Patent Publication Number: US-11379530-B2

Title: Leveraging references values in inverted indexes to retrieve associated event records comprising raw machine data

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a Continuation-in-part of, claims the benefit of and priority to U.S. application Ser. No. 15/421,293, filed Jan. 31, 2017, entitled “USING AN INVERTED INDEX IN A PIPELINED SEARCH QUERY TO DETERMINE A SET OF EVENT DATA THAT IS FURTHER LIMITED BY FILTERING AND/OR PROCESSING OF SUBSEQUENT QUERY PIPESTAGES,” and hereby incorporated by reference in its entirety. 
    
    
     BACKGROUND 
     The rapid increase in the production and collection of machine generated data has created relatively large data sets that are difficult to search. The machine data can include sequences of time stamped records that may occur in one or more usually continuous streams. Further, machine data often represents some type of activity made up of discrete events. 
     Searching data requires different ways to express searches. Search engines today allow users to search by the most frequently occurring terms or keywords within the data and generally have little notion of event based searching. Given the large volume and repetitive characteristics of machine data, users often need to start by narrowing the set of potential search results using event-based search mechanisms and then, through examination of the results, choose one or more keywords to add to their search parameters. Timeframes and event-base metadata like frequency, distribution, and likelihood of occurrence are especially important when searching data, but difficult to achieve with current search engine approaches. 
     Also, users often generate arbitrary queries to produce statistics and metrics about selected data fields that may be included in the data. Indexing may enable raw data records to be identified quickly, but operations that examine/scan the individual data records may become prohibitively expensive as the size of the data set grows. Certain Extract, Transform, Load (ETL) based database systems in use today allow for data to be transformed during the data ingestion process for storing in a proper format and structure for purposes of querying and analysis. The shortcoming of such database systems is that certain information, e.g., select data fields not designated for extraction by a user at data ingestion time, is discarded and, therefore, cannot be retrieved if required at a later time. Consequently, a user needs to pre-specify the data fields that need to be extracted from the raw data records at data ingestion time which makes these database systems rather inflexible. As storage capacity becomes cheaper, there are fewer incentives to discard the unused portions of the raw data records. Thus, systems that can search relatively large sets of data are the subject of considerable innovation. 
     SUMMARY 
     This Summary is provided to introduce a selection of concepts in a simplified form that is further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. 
     Performing extraction and analysis operations at search time in an event-based data intake and query system can involve a large amount of data and require a large number of computational operations, which can cause delays in processing queries. One way to reduce the amount of time it takes to perform these operations at search time is to use inverted indexes. 
     An inverted index (also known as a “summarization table”) contains entries for specific field-value pairs and can be created to address queries that are frequently encountered or computationally intensive. The inverted index also comprises one or more reference values associated with a field-value pair, where the reference value references the location of a source event record in a field searchable data store containing the field-value pair, where the field searchable data store stores all the event records. Creating the inverted index data structure avoids the computational overhead each time an event record needs to be retrieved and searched from the field searchable data store. 
     In order to expedite queries, in some embodiments, the search engine will employ the inverted index separate from the raw record data store to generate responses to the received queries. In other embodiments, the search engine may employ the inverted index to leverage the posting values therein to provide faster and more efficient access to the raw event records. 
     According to one or more embodiments of the present invention, a method is provided for leveraging reference values in inverted indexes to retrieve and search associated event records comprising raw machine data. The method comprises accessing a query associated with a first set of event records in a field searchable data store comprising a plurality of event records, each event record comprising a time-stamped portion of raw machine data. Further, the method comprises evaluating the query. Responsive to a determination that the query is a pipelined query comprising a plurality of pipe-stages, the method comprises generating results for the query, wherein the generating comprises: (a) responsive to a first pipe-stage of the query, accessing an inverted index, wherein each entry in the inverted index comprises at least one field from a plurality of fields operable to be extracted from each of the first set of event records, a corresponding at least one field value and a reference value associated with the at least one field and corresponding field value that identifies a location in the field searchable data store where an associated event record in the first set of event records is stored; (b) responsive to a second pipe-stage of the query, performing a search to filter out a second set of event records from the first set of event records; and (c) retrieving the second set of event records from the field searchable data store using reference values in the inverted index. 
     In another embodiment, the method further comprises displaying the second set of event records in a user-interface, wherein the displaying comprises displaying the time-stamped portion of raw machine data comprised within each of the second set of event records. 
     In one embodiment, performing a search further comprises: (a) responsive to a determination that the second pipe-stage of the query comprises a predicate referencing the at least one field, evaluating the predicate against the at least one field and the corresponding field value in each entry within the inverted index; and (b) in accordance with the evaluating, determining the second set of event records to retrieve from the field searchable data store using the reference values in the inverted index. 
     In a different embodiment, performing a search further comprises: (a) responsive to a determination that the second pipe-stage of the query comprises a predicate that references a field not indexed in the inverted index, accessing the first set of event records in the field searchable data store; and (b) evaluating the predicate against the plurality of fields and corresponding field values extracted from the raw machine data in the first set of event records during the performing of the search to filter out the second set of event records. 
     In one embodiment, responsive to a determination that the pipelined query does not comprise a plurality of pipe-stages, generating results for the query, wherein the generating comprises: (a) responsive to the query, accessing the inverted index; (b) retrieving the first set of event records from the field searchable data store using the reference values in the inverted index; and (c) displaying the first set of event records in a display. 
     In another embodiment, the method further comprises producing a third set of event records by performing filtering operations on the second set of event records responsive to a third stage of the query. 
     In one embodiment, the method further comprises performing a statistical calculation using the plurality of fields and corresponding values extracted from the second set of event records responsive to a third stage of the query. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the drawings: 
         FIG. 1  illustrates a networked computer environment in which an embodiment may be implemented. 
         FIG. 2  illustrates a block diagram of an example data intake and query system in which an embodiment may be implemented. 
         FIG. 3  is a flow diagram that illustrates how indexers process, index, and store data received from forwarders in accordance with the disclosed embodiments. 
         FIG. 4  is a flow diagram that illustrates how a search head and indexers perform a search query in accordance with the disclosed embodiments. 
         FIG. 5  illustrates a scenario where a common customer ID is found among log data received from three disparate sources in accordance with the disclosed embodiments. 
         FIG. 6A  illustrates a search screen in accordance with the disclosed embodiments. 
         FIG. 6B  illustrates a data summary dialog that enables a user to select various data sources in accordance with the disclosed embodiments. 
         FIG. 7  illustrates a user interface screen for an example data model-driven report generation interface in accordance with the disclosed embodiments. 
         FIG. 8  illustrates an example search query received from a client and executed by search peers in accordance with the disclosed embodiments. 
         FIG. 9A  illustrates a key indicators view in accordance with the disclosed embodiments. 
         FIG. 9B  illustrates an incident review dashboard in accordance with the disclosed embodiments. 
         FIG. 9C  illustrates a proactive monitoring tree in accordance with the disclosed embodiments. 
         FIG. 9D  illustrates a user interface screen displaying both log data and performance data in accordance with the disclosed embodiments. 
         FIG. 10  illustrates a block diagram of an example cloud-based data intake and query system in which an embodiment may be implemented. 
         FIG. 11  illustrates a block diagram of an example data intake and query system that performs searches across external data systems in accordance with the disclosed embodiments. 
         FIG. 12  illustrates an exemplary manner in which time-stamped event data can be stored in a data store in accordance with the disclosed embodiments. 
         FIG. 13  provides a visual representation of the manner in which a pipelined search language or query operates in accordance with the disclosed embodiments. 
         FIG. 14  illustrates the manner in which keyword searches and field searches are processed in accordance with disclosed embodiments. 
         FIG. 15  illustrates the manner in which an inverted index is created and used in accordance with the disclosed embodiments. 
         FIG. 16  presents a flowchart illustrating how an inverted index in a pipelined search query can be used to determine a set of event data that can be further processed in accordance with the disclosed embodiments. 
         FIG. 17  illustrates the manner in which an inverted index may be used to retrieve related event records efficiently in response to a query in accordance with the disclosed embodiments. 
         FIG. 18  presents a flowchart illustrating how an inverted index may be used to retrieve related event records efficiently in response to a query in accordance with the disclosed embodiments. 
         FIG. 19A  illustrates a set of event records that may be stored in a bucket data structure comprised within a raw record data store in accordance with the disclosed embodiments. 
         FIG. 19B  illustrates a data model created by specifying search constraints for the events in  FIG. 19A  and accelerating the data model using a summarization table in accordance with the disclosed embodiments. 
         FIG. 19C  illustrates the manner in which a query invoking the accelerated data model of  FIG. 19B  and comprising a predicate with a structured field may be processed in accordance with the disclosed embodiments. 
         FIG. 20A  illustrates an exemplary user interface with a set of event records that may be stored in a raw record data store in accordance with the disclosed embodiments. 
         FIG. 20B  illustrates an exemplary user interface for defining constraints for a data model created using the events of  FIG. 20A  in accordance with the disclosed embodiments. 
         FIG. 20C  illustrates an exemplary user interface showing the manner in which events in the data model of  FIG. 20B  may be retrieved and annotated with structured field in accordance with the disclosed embodiments. 
         FIG. 20D  illustrates an exemplary user interface showing the manner in which a query invoking the accelerated data model of  20 B and comprising a predicate with a structured field may be processed in accordance with the disclosed embodiments. 
         FIG. 21  presents a flowchart illustrating a computer implemented process in which structured fields may be emitted in response to a search of an accelerated data model in accordance with the disclosed embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments are described herein according to the following outline: 
     1.0. General Overview 
     2.0. Operating Environment
         2.1. Host Devices   2.2. Client Devices   2.3. Client Device Applications   2.4. Data Server System   2.5. Data Ingestion
           2.5.1. Input   2.5.2. Parsing   2.5.3. Indexing   
           2.6. Query Processing   2.7 Pipelined Search Language   2.8. Field Extraction Using A Configuration File   2.9. Example Search Screen   2.10. Data Modelling   2.11. Acceleration Techniques
           2.11.1. Aggregation Technique   2.11.2. Keyword Index   2.11.3. High Performance Analytics Store
               2.11.3.1 Extracting Event Data Using Posting Values   2.11.3.2 Leveraging Reference Values In An Inverted Index To Retrieve Associated Event Data   2.11.3.3 Accelerating Data Models Using Summarization Tables   
               2.11.4. Accelerating Report Generation   
           2.12. Security Features   2.13. Data Center Monitoring   2.14. Cloud-Based System Overview   2.14. Searching Externally Archived Data
           2.14.1. ERP Process Features   
               

     1.0. General Overview 
     Modern data centers and other computing environments can comprise anywhere from a few host computer systems to thousands of systems configured to process data, service requests from remote clients, and perform numerous other computational tasks. During operation, various components within these computing environments often generate significant volumes of machine-generated data. For example, machine data is generated by various components in the information technology (IT) environments, such as servers, sensors, routers, mobile devices, virtual machines, operating systems, Internet of Things (IoT) devices, etc. Machine-generated data can include system logs, network packet data, sensor data, application program data, error logs, stack traces, system performance data, etc. In general, machine-generated data can also include performance data, diagnostic information, and many other types of data that can be analyzed to diagnose performance problems, monitor user interactions, and to derive other insights. 
     A number of tools are available to analyze raw machine data, that is, machine-generated data. In order to reduce the size of the potentially vast amount of machine data that may be generated, many of these tools typically pre-process the data based on anticipated data-analysis needs. For example, pre-specified data items may be extracted from the machine data and stored in a database to facilitate efficient retrieval and analysis of those data items at search time. However, the rest of the machine data typically is not saved and discarded during pre-processing. As storage capacity becomes progressively cheaper and more plentiful, there are fewer incentives to discard these portions of machine data and many reasons to retain more of the data. 
     This plentiful storage capacity is presently making it feasible to store massive quantities of minimally processed machine data for later retrieval and analysis. In general, storing minimally processed machine data and performing analysis operations at search time can provide greater flexibility because it enables an analyst to search all of the machine data, instead of searching only a pre-specified set of data items. This may enable an analyst to investigate different aspects of the machine data that previously were unavailable for analysis. 
     However, analyzing and searching massive quantities of machine data presents a number of challenges. For example, a data center, servers, or network appliances may generate many different types and formats of machine data (e.g., system logs, network packet data (e.g., wire data, etc.), sensor data, application program data, error logs, stack traces, system performance data, operating system data, virtualization data, etc.) from thousands of different components, which can collectively be very time-consuming to analyze. Further, new machine data is being produced in real-time, which requires that any searching or analysis of the data needs to be dynamic and updated continuously. By way of example, a server may be interacting with many different types of components in the IT environment in real-time, e.g., client device, operating system, routers, firewalls, etc. Each of the components may be producing log files with information regarding its interaction with the server in a different format. In order to determine if the server is secure, for example, data exchanged with all the various components needs to be analyzed and correlated in real-time. In another example, mobile devices may generate large amounts of information relating to data accesses, application performance, operating system performance, network performance, etc. There can be millions of mobile devices that report these types of information. 
     These challenges can be addressed by using an event-based data intake and query system, such as the SPLUNK® ENTERPRISE system developed by Splunk Inc. of San Francisco, Calif. The SPLUNK® ENTERPRISE system is the leading platform for providing real-time operational intelligence that enables organizations to collect, index, and search machine-generated data from various websites, applications, servers, networks, and mobile devices that power their businesses. The SPLUNK® ENTERPRISE system is particularly useful for analyzing data which is commonly found in system log files, network data, and other data input sources. Although many of the techniques described herein are explained with reference to a data intake and query system similar to the SPLUNK® ENTERPRISE system, these techniques are also applicable to other types of data systems. 
     In the SPLUNK® ENTERPRISE system, machine-generated data are collected and stored as “events”. An event comprises a portion of the machine-generated data and is associated with a specific point in time. For example, events may be derived from “time series data,” where the time series data comprises a sequence of data points (e.g., performance measurements from a computer system, etc.) that are associated with successive points in time. In general, each event can be associated with a timestamp that is derived from the raw data in the event, determined through interpolation between temporally proximate events having known timestamps, or determined based on other configurable rules for associating timestamps with events, etc. 
     In some instances, machine data can have a predefined format, where data items with specific data formats are stored at predefined locations in the data. For example, the machine data may include data stored as fields in a database table. In other instances, machine data may not have a predefined format, that is, the data is not at fixed, predefined locations, but the data does have repeatable patterns and is not random. This means that some machine data can comprise various data items of different data types and that may be stored at different locations within the data. For example, when the data source is an operating system log, an event can include one or more lines from the operating system log containing raw data that includes different types of performance and diagnostic information associated with a specific point in time. 
     Examples of components which may generate machine data from which events can be derived include, but are not limited to, web servers, application servers, databases, firewalls, routers, operating systems, and software applications that execute on computer systems, mobile devices, sensors, Internet of Things (IoT) devices, etc. The data generated by such data sources can include, for example and without limitation, server log files, activity log files, configuration files, messages, network packet data, performance measurements, sensor measurements, etc. 
     The SPLUNK® ENTERPRISE system uses flexible schema to specify how to extract information from the event data. A flexible schema may be developed and redefined as needed. Note that a flexible schema may be applied to event data “on the fly,” when it is needed (e.g., at search time, index time, ingestion time, etc.). When the schema is not applied to event data until search time it may be referred to as a “late-binding schema.” 
     During operation, the SPLUNK® ENTERPRISE system starts with raw input data (e.g., one or more system logs, streams of network packet data, sensor data, application program data, error logs, stack traces, system performance data, etc.). The system divides this raw data into blocks (e.g., buckets of data, each associated with a specific time frame, etc.), and parses the raw data to produce timestamped events. The system stores the timestamped events in a data store. The system enables users to run queries against the stored data to, for example, retrieve events that meet criteria specified in a query, such as containing certain keywords or having specific values in defined fields. As used herein throughout, data that is part of an event is referred to as “event data”. In this context, the term “field” refers to a location in the event data containing one or more values for a specific data item. As will be described in more detail herein, the fields are defined by extraction rules (e.g., regular expressions) that derive one or more values from the portion of raw machine data in each event that has a particular field specified by an extraction rule. The set of values so produced are semantically-related (such as IP address), even though the raw machine data in each event may be in different formats (e.g., semantically-related values may be in different positions in the events derived from different sources). 
     As noted above, the SPLUNK® ENTERPRISE system utilizes a late-binding schema to event data while performing queries on events. One aspect of a late-binding schema is applying “extraction rules” to event data to extract values for specific fields during search time. More specifically, the extraction rules for a field can include one or more instructions that specify how to extract a value for the field from the event data. An extraction rule can generally include any type of instruction for extracting values from data in events. In some cases, an extraction rule comprises a regular expression where a sequence of characters form a search pattern, in which case the rule is referred to as a “regex rule.” The system applies the regex rule to the event data to extract values for associated fields in the event data by searching the event data for the sequence of characters defined in the regex rule. In some embodiments, an extraction rule may be identified automatically (e.g., auto-discovery) or by being specified within a particular file (e.g., a configuration file). In the same or alternative embodiments, an extraction rule may also be defined by a search query. For example, the search query may define a field and may further perform computations that may be named as fields. 
     In the SPLUNK® ENTERPRISE system, a field extractor may be configured to automatically generate extraction rules for certain field values in the events when the events are being created, indexed, or stored, or possibly at a later time. Alternatively, a user may manually define extraction rules for fields using a variety of techniques. In contrast to a conventional schema for a database system, a late-binding schema is not defined at data ingestion time. Instead, the late-binding schema can be developed on an ongoing basis until the time a query is actually executed. This means that extraction rules for the fields in a query may be provided in the query itself, or may be located during execution of the query. Hence, as a user learns more about the data in the events, the user can continue to refine the late-binding schema by adding new fields, deleting fields, or modifying the field extraction rules for use the next time the schema is used by the system. Because the SPLUNK® ENTERPRISE system maintains the underlying raw data and uses late-binding schema for searching the raw data, it enables a user to continue investigating and learn valuable insights about the raw data. 
     In contrast to a conventional schema for a database system, a late-binding schema is not defined at data ingestion time. Instead, the late-binding schema can be developed on an ongoing basis until the time a query is actually executed. This means that extraction rules for the fields in a query may be provided in the query itself, or may be located during execution of the query. Hence, as an analyst learns more about the data in the events, the analyst can continue to refine the late-binding schema by adding new fields, deleting fields, or changing the field extraction rules until the next time the schema is used by a query. Because the SPLUNK® ENTERPRISE system maintains the underlying raw data and provides a late-binding schema for searching the raw data, it enables an analyst to investigate questions that arise as the analyst learns more about the events. 
     In some embodiments, a common field name may be used to reference two or more fields containing equivalent data items, even though the fields may be associated with different types of events that possibly have different data formats and different extraction rules. By enabling a common field name to be used to identify equivalent fields from different types of events generated by disparate data sources, the system facilitates use of a “common information model” (CIM) across the disparate data sources (further discussed with respect to  FIG. 5 ). 
     2.0. Operating Environment 
       FIG. 1  illustrates a networked computer system  100  in which an embodiment may be implemented. Those skilled in the art would understand that  FIG. 1  represents one example of a networked computer system and other embodiments may use different arrangements. 
     The networked computer system  100  comprises one or more computing devices. These one or more computing devices comprise any combination of hardware and software configured to implement the various logical components described herein. For example, the one or more computing devices may include one or more memories that store instructions for implementing the various components described herein, one or more hardware processors configured to execute the instructions stored in the one or more memories, and various data repositories in the one or more memories for storing data structures utilized and manipulated by the various components. 
     In an embodiment, one or more client devices  102  are coupled to one or more host devices  106  and a data intake and query system  108  via one or more networks  104 . Networks  104  broadly represent one or more LANs, WANs, cellular networks (e.g., LTE, HSPA, 3G, and other cellular technologies), or networks using any of wired, wireless, terrestrial microwave, or satellite links, and may include the public Internet. 
     2.1. Host Devices 
     In the illustrated embodiment, a system  100  includes one or more host devices  106 . Host devices  106  may broadly include any number of computers, virtual machine instances, or data centers that are configured to host or execute one or more instances of host applications  114 . In general, a host device  106  may be involved, directly or indirectly, in processing requests received from client devices  102 . Each host device  106  may comprise, for example, one or more of a network device, a web server, an application server, a database server, etc. A collection of host devices  106  may be configured to implement a network-based service. For example, a provider of a network-based service may configure one or more host devices  106  and host applications  114  (e.g., one or more web servers, application servers, database servers, etc.) to collectively implement the network-based application. 
     In general, client devices  102  communicate with one or more host applications  114  to exchange information. The communication between a client device  102  and a host application  114  may, for example, be based on the Hypertext Transfer Protocol (HTTP) or any other network protocol. Content delivered from the host application  114  to a client device  102  may include, for example, HTML documents, media content, etc. The communication between a client device  102  and host application  114  may include sending various requests and receiving data packets. For example, in general, a client device  102  or application running on a client device may initiate communication with a host application  114  by making a request for a specific resource (e.g., based on an HTTP request), and the application server may respond with the requested content stored in one or more response packets. 
     In the illustrated embodiment, one or more of host applications  114  may generate various types of performance data during operation, including event logs, network data, sensor data, and other types of machine-generated data. For example, a host application  114  comprising a web server may generate one or more web server logs in which details of interactions between the web server and any number of client devices  102  is recorded. As another example, a host device  106  comprising a router may generate one or more router logs that record information related to network traffic managed by the router. As yet another example, a host application  114  comprising a database server may generate one or more logs that record information related to requests sent from other host applications  114  (e.g., web servers or application servers) for data managed by the database server. 
     2.2. Client Devices 
     Client devices  102  of  FIG. 1  represent any computing device capable of interacting with one or more host devices  106  via a network  104 . Examples of client devices  102  may include, without limitation, smart phones, tablet computers, handheld computers, wearable devices, laptop computers, desktop computers, servers, portable media players, gaming devices, and so forth. In general, a client device  102  can provide access to different content, for instance, content provided by one or more host devices  106 , etc. Each client device  102  may comprise one or more client applications  110 , described in more detail in a separate section hereinafter. 
     2.3. Client Device Applications 
     In an embodiment, each client device  102  may host or execute one or more client applications  110  that are capable of interacting with one or more host devices  106  via one or more networks  104 . For instance, a client application  110  may be or comprise a web browser that a user may use to navigate to one or more websites or other resources provided by one or more host devices  106 . As another example, a client application  110  may comprise a mobile application or “app.” For example, an operator of a network-based service hosted by one or more host devices  106  may make available one or more mobile apps that enable users of client devices  102  to access various resources of the network-based service. As yet another example, client applications  110  may include background processes that perform various operations without direct interaction from a user. A client application  110  may include a “plug-in” or “extension” to another application, such as a web browser plug-in or extension. 
     In an embodiment, a client application  110  may include a monitoring component  112 . At a high level, the monitoring component  112  comprises a software component or other logic that facilitates generating performance data related to a client device&#39;s operating state, including monitoring network traffic sent and received from the client device and collecting other device or application-specific information. Monitoring component  112  may be an integrated component of a client application  110 , a plug-in, an extension, or any other type of add-on component. Monitoring component  112  may also be a stand-alone process. 
     In one embodiment, a monitoring component  112  may be created when a client application  110  is developed, for example, by an application developer using a software development kit (SDK). The SDK may include custom monitoring code that can be incorporated into the code implementing a client application  110 . When the code is converted to an executable application, the custom code implementing the monitoring functionality can become part of the application itself. 
     In some cases, an SDK or other code for implementing the monitoring functionality may be offered by a provider of a data intake and query system, such as a system  108 . In such cases, the provider of the system  108  can implement the custom code so that performance data generated by the monitoring functionality is sent to the system  108  to facilitate analysis of the performance data by a developer of the client application or other users. 
     In an embodiment, the custom monitoring code may be incorporated into the code of a client application  110  in a number of different ways, such as the insertion of one or more lines in the client application code that call or otherwise invoke the monitoring component  112 . As such, a developer of a client application  110  can add one or more lines of code into the client application  110  to trigger the monitoring component  112  at desired points during execution of the application. Code that triggers the monitoring component may be referred to as a monitor trigger. For instance, a monitor trigger may be included at or near the beginning of the executable code of the client application  110  such that the monitoring component  112  is initiated or triggered as the application is launched, or included at other points in the code that correspond to various actions of the client application, such as sending a network request or displaying a particular interface. 
     In an embodiment, the monitoring component  112  may monitor one or more aspects of network traffic sent or received by a client application  110 . For example, the monitoring component  112  may be configured to monitor data packets transmitted to or from one or more host applications  114 . Incoming or outgoing data packets can be read or examined to identify network data contained within the packets, for example, and other aspects of data packets can be analyzed to determine a number of network performance statistics. Monitoring network traffic may enable information to be gathered particular to the network performance associated with a client application  110  or set of applications. 
     In an embodiment, network performance data refers to any type of data that indicates information about the network or network performance. Network performance data may include, for instance, a URL requested, a connection type (e.g., HTTP, HTTPS, etc.), a connection start time, a connection end time, an HTTP status code, request length, response length, request headers, response headers, connection status (e.g., completion, response time(s), failure, etc.), and the like. Upon obtaining network performance data indicating performance of the network, the network performance data can be transmitted to a data intake and query system  108  for analysis. 
     Upon developing a client application  110  that incorporates a monitoring component  112 , the client application  110  can be distributed to client devices  102 . Applications generally can be distributed to client devices  102  in any manner, or they can be pre-loaded. In some cases, the application may be distributed to a client device  102  via an application marketplace or other application distribution system. For instance, an application marketplace or other application distribution system might distribute the application to a client device based on a request from the client device to download the application. 
     Examples of functionality that enables monitoring performance of a client device are described in U.S. patent application Ser. No. 14/524,748, entitled “UTILIZING PACKET HEADERS TO MONITOR NETWORK TRAFFIC IN ASSOCIATION WITH A CLIENT DEVICE”, filed on 27 Oct. 2014, and which is hereby incorporated by reference in its entirety for all purposes. 
     In an embodiment, the monitoring component  112  may also monitor and collect performance data related to one or more aspects of the operational state of a client application  110  or client device  102 . For example, a monitoring component  112  may be configured to collect device performance information by monitoring one or more client device operations, or by making calls to an operating system or one or more other applications executing on a client device  102  for performance information. Device performance information may include, for instance, a current wireless signal strength of the device, a current connection type and network carrier, current memory performance information, a geographic location of the device, a device orientation, and any other information related to the operational state of the client device. 
     In an embodiment, the monitoring component  112  may also monitor and collect other device profile information including, for example, a type of client device, a manufacturer and model of the device, versions of various software applications installed on the device, and so forth. 
     In general, a monitoring component  112  may be configured to generate performance data in response to a monitor trigger in the code of a client application  110  or other triggering application event, as described above, and to store the performance data in one or more data records. Each data record, for example, may include a collection of field-value pairs, each field-value pair storing a particular item of performance data in association with a field for the item. For example, a data record generated by a monitoring component  112  may include a “networkLatency” field (not shown in the Figure) in which a value is stored. This field indicates a network latency measurement associated with one or more network requests. The data record may include a “state” field to store a value indicating a state of a network connection, and so forth for any number of aspects of collected performance data. 
     2.4. Data Server System 
       FIG. 2  depicts a block diagram of an exemplary data intake and query system  108 , similar to the SPLUNK® ENTERPRISE system. System  108  includes one or more forwarders  204  that receive raw machine data from a variety of input data sources  202 , and one or more indexers  206  that process and store the data in one or more data stores  208 . These forwarders and indexers can comprise separate computer systems, or may alternatively comprise separate processes executing on one or more computer systems. 
     Each data source  202  broadly represents a distinct source of data that can be consumed by a system  108 . Examples of a data source  202  include, without limitation, data files, directories of files, data sent over a network, event logs, registries, etc. 
     During operation, the forwarders  204  identify which indexers  206  receive data collected from a data source  202  and forward the data to the appropriate indexers. Forwarders  204  can also perform operations on the data before forwarding, including removing extraneous data, detecting timestamps in the data, parsing data, indexing data, routing data based on criteria relating to the data being routed, or performing other data transformations. 
     In an embodiment, a forwarder  204  may comprise a service accessible to client devices  102  and host devices  106  via a network  104 . For example, one type of forwarder  204  may be capable of consuming vast amounts of real-time data from a potentially large number of client devices  102  or host devices  106 . The forwarder  204  may, for example, comprise a computing device which implements multiple data pipelines or “queues” to handle forwarding of network data to indexers  206 . A forwarder  204  may also perform many of the functions that are performed by an indexer. For example, a forwarder  204  may perform keyword extractions on raw data or parse raw data to create events. A forwarder  204  may generate time stamps for events. Additionally or alternatively, a forwarder  204  may perform routing of events to indexers. Data store  208  may contain events derived from machine data from a variety of sources all pertaining to the same component in an IT environment, and this data may be produced by the machine in question or by other components in the IT environment. 
     2.5. Data Ingestion 
       FIG. 3  depicts a flow chart illustrating an example data flow performed by Data Intake and Query system  108 , in accordance with the disclosed embodiments. The data flow illustrated in  FIG. 3  is provided for illustrative purposes only; those skilled in the art would understand that one or more of the steps of the processes illustrated in  FIG. 3  may be removed or the ordering of the steps may be changed. Furthermore, for the purposes of illustrating a clear example, one or more particular system components are described in the context of performing various operations during each of the data flow stages. For example, a forwarder is described as receiving and processing data during an input phase; an indexer is described as parsing and indexing data during parsing and indexing phases; and a search head is described as performing a search query during a search phase. However, other system arrangements and distributions of the processing steps across system components may be used. 
     2.5.1. Input 
     At block  302 , a forwarder receives raw machine data from an input source, such as a data source  202  shown in  FIG. 2 . A forwarder initially may receive the data as a raw data stream generated by the input source. For example, a forwarder may receive a data stream from a log file generated by an application server, from a stream of network data from a network device, or from any other source of data. In one embodiment, a forwarder receives the raw data and may segment the data stream into “blocks”, or “buckets,” possibly of a uniform data size, to facilitate subsequent processing steps. 
     At block  304 , a forwarder or other system component annotates each block generated from the raw data with one or more metadata fields. These metadata fields may, for example, provide information related to the data block as a whole and may apply to each event that is subsequently derived from the data in the data block. For example, the metadata fields may include separate fields specifying each of a host, a source, and a source type related to the data block. A host field may contain a value identifying a host name or IP address of a device that generated the data. A source field may contain a value identifying a source of the data, such as a pathname of a file, the name of the file, stream, or a protocol and port related to received network data. A source type field may contain a value specifying a particular source type label for the data. Additional metadata fields may also be included during the input phase, such as a character encoding of the data, if known, and possibly other values that provide information relevant to later processing steps. In an embodiment, a forwarder forwards the annotated data blocks to another system component (typically an indexer) for further processing. 
     The SPLUNK® ENTERPRISE system allows forwarding of data from one SPLUNK® ENTERPRISE instance to another, or even to a third-party system. SPLUNK® ENTERPRISE system can employ different types of forwarders in a configuration. 
     In an embodiment, a forwarder may contain the essential components needed to forward data. It can gather data from a variety of inputs and forward the data to a SPLUNK® ENTERPRISE server for indexing and searching. It also can tag metadata (e.g., source, source type, host, etc.). 
     Additionally or optionally, in an embodiment, a forwarder has the capabilities of the aforementioned forwarder as well as additional capabilities. The forwarder can parse data before forwarding the data (e.g., associate a time stamp with a portion of data and create an event, etc.) and can route data based on criteria such as source or type of event. It can also index data locally while forwarding the data to another indexer. 
     2.5.2. Parsing 
     At block  306 , an indexer receives data blocks from a forwarder and parses the data to organize the data into events. This process is referred to as “event breaking” which, in one embodiment, may involve breaking up the data blocks at regularly occurring time-stamps within the raw data using a pattern-matching algorithm. 
     In an embodiment, to organize the data into events, an indexer may determine a source type associated with each data block (e.g., by extracting a source type label from the metadata fields associated with the data block, etc.) and refer to a source type configuration corresponding to the identified source type. A source type can either be well known, e.g., HTTP Web server logs, Windows event logs, etc. or can be created by the user. The source type definition may include one or more properties that indicate to the indexer to automatically determine the boundaries of events within the data. In general, these properties may include regular expression-based rules or delimiter rules where, for example, event boundaries may be indicated by predefined characters or character strings. These predefined characters may include punctuation marks or other special characters including, for example, carriage returns, tabs, spaces, line breaks, etc. If a source type for the data is unknown to the indexer, an indexer may infer a source type for the data by examining the structure of the data. Then, it can apply an inferred source type definition to the data to create the events. 
     At block  308 , the indexer determines a timestamp for each event. Similar to the process for creating events, an indexer may again refer to a source type definition associated with the data to locate one or more properties that indicate instructions for determining a timestamp for each event. The properties may, for example, instruct an indexer to extract a time value from a portion of data in the event, to interpolate time values based on timestamps associated with temporally proximate events, to create a timestamp based on a time the event data was received or generated, to use the timestamp of a previous event, or use any other rules for determining timestamps. 
     At block  310 , the indexer associates with each event one or more metadata fields including a field containing the timestamp (in some embodiments, a timestamp may be included in the metadata fields) determined for the event. These metadata fields may include a number of “default fields” that are associated with all events, and may also include one more custom fields as defined by a user. Similar to the metadata fields associated with the data blocks at block  304 , the default metadata fields associated with each event may include a host, source, and source type field including or in addition to a field storing the timestamp. Note, however, that other default fields may be extracted during index time as well. 
     At block  312 , an indexer may optionally apply one or more transformations to data included in the events created at block  306 . For example, such transformations can include removing a portion of an event (e.g., a portion used to define event boundaries, extraneous characters from the event, other extraneous text, etc.), masking a portion of an event (e.g., masking a credit card number), removing redundant portions of an event, etc. The transformations applied to event data may, for example, be specified in one or more configuration files and referenced by one or more source type definitions. 
       FIG. 12  illustrates an exemplary manner in which time-stamped event data can be stored in a data store in accordance with the disclosed embodiments. As mentioned above, certain metadata fields (also known as indexed fields), e.g., host  1210 , source  1211 , source type  1212  and timestamps  1214  are generated for each event, and associated with a corresponding event when storing the event data in a data store, e.g., data store  208 . The metadata can be extracted from the raw machine data, or supplied or defined by an entity, such as a user or computer system. The metadata or indexed fields can become part of the event data. Note that while the time-stamp metadata field can be extracted from the raw data associated with each event, the values for the other metadata fields may be determined by the indexer based on information it receives pertaining to the source of the data. 
     As noted above, the metadata or indexed fields  1210 ,  1211 , and  1212  may be “default fields” that are associated with all events. However, the event data may include one more other custom indexed fields as defined by a user that can be indexed and also stored along with the event data  1213 . In other words, other default fields may be extracted during index time as well. 
     Even though certain default or user-defined metadata fields can be extracted from the raw data for indexing purposes, e.g., time-based data, all the raw machine data within each event can be maintained in its original condition. In other words, unless certain information needs to be removed for practical reasons (e.g. extraneous information, confidential information), all the raw machine data associated with an event can be preserved and saved in the data store in field  1213  as shown in  FIG. 12 . Accordingly, the data store in which the event records are stored is sometimes referred to as a “raw record data store.” The raw record data store contains a record of the raw event data tagged with the various default fields. 
     Referring back to  FIG. 12 , events  1221 ,  1222  and  1223  are associated with a server access log that records all requests from multiple clients that have been processed by the server. Each of the events  1221 - 1223  is associated with a discrete request made from a client device. The raw data associated with an event extracted from a server access log will comprise the IP address of the client  1203 , the user id of the person requesting the document  1204 , the time the server finished processing the request  1205 , the request line from the client  1206 , the status code returned by the server to the client  1207 , the size of the object returned to the client (in this case, the gif file requested by the client)  1208  and the time spent to serve the request in microseconds  1209 . As seen in  FIG. 12 , all the raw data retrieved from the server access log is retained and stored as part of each event in the data store. 
     Event  1224  is associated with an entry in a server error log that records any errors that the server encountered when processing a client request. Similar to the events related to the server access log, all the raw data in the error log file pertaining to this event is preserved and stored as part of the event record  1224 . 
     Saving minimally processed event data in a data store and associating it with metadata fields in the manner shown in  FIG. 12  is advantageous because it allows a search analyst to search all the machine data at search time instead of searching only a pre-specified set of data items. As mentioned above, because the system maintains the underlying raw data and uses a late-binding schema for searching the raw data, it enables a user to continue investigating and learn valuable insights about the raw data. In other words, the user is not compelled to know about all the fields of information that will be needed at data ingestion time. As a user learns more about the data in the events, the user can continue to refine the late-binding schema by adding new fields, deleting fields, or modifying the field extraction rules for use the next time the schema is used by the system. 
     2.5.3. Indexing 
     At blocks  314  and  316 , an indexer can optionally generate a keyword index to facilitate fast keyword searching for event data. To build a keyword index, at block  314 , the indexer identifies a set of keywords in each event. At block  316 , the indexer includes the identified keywords in an index, which associates each stored keyword with reference pointers to events containing that keyword (or to locations within events where that keyword is located, other location identifiers, etc.). When an indexer subsequently receives a keyword-based query, the indexer can access the keyword index to quickly identify events containing the keyword. 
     In some embodiments, the keyword index may include entries for name-value pairs found in events, where a name-value pair can include a pair of keywords connected by a symbol, such as an equals sign or colon. This way, events containing these name-value pairs can be quickly located. In some embodiments, fields can automatically be generated for some or all of the name-value pairs at the time of indexing. For example, if the string “dest=10.0.1.2” is found in an event, a field named “dest” may be created for the event, and assigned a value of “10.0.1.2”. 
     At block  318 , the indexer stores the events with an associated timestamp in a data store  208 . Timestamps enable a user to search for events based on a time range, thereby, making the search process time-sensitive and efficient. In one embodiment, the stored events are organized into “buckets,” where each bucket stores events associated with a specific time range based on the timestamps associated with each event. Organizing events into buckets optimizes time-based searching because it allows an indexer to search only the relevant buckets when responding to a query. It also allows for events with recent timestamps, which may have a higher likelihood of being accessed, to be stored in a faster memory to facilitate faster retrieval. In one or more embodiments, buckets can be designated as “hot,” “warm,” or “cold” depending on the time range of the events contained within them. For example, a bucket may be designated “hot” if it is still open and accepting new incoming events. A bucket may be designated “warm” if it is not accepting any more new data and its time range has been finalized. Further, a bucket may be designated “cold” if the data it contains is historical and can be archived in slower memory. The “hot” and “warm” buckets, for example, may be stored in faster flash memory, while the “cold” buckets may be stored on a hard disk. 
     Each indexer  206  may be responsible for storing and searching a subset of the events contained in a corresponding data store  208 . By distributing events among the indexers and data stores, the indexers can analyze events for a query in parallel. For example, using map-reduce techniques, each indexer returns partial responses for a subset of events to a search head that combines the results to produce an answer for the query. By storing events in buckets for specific time ranges, an indexer may further optimize data retrieval process by searching buckets corresponding to time ranges that are relevant to a query. 
     Moreover, events and buckets can also be replicated across different indexers and data stores to facilitate high availability and disaster recovery as described in U.S. patent application Ser. No. 14/266,812, entitled “SITE-BASED SEARCH AFFINITY”, filed on 30 Apr. 2014, and in U.S. patent application Ser. No. 14/266,817, entitled “MULTI-SITE CLUSTERING”, also filed on 30 Apr. 2014, each of which is hereby incorporated by reference in its entirety for all purposes. 
     2.6. Query Processing 
       FIG. 4  is a flow diagram that illustrates an exemplary process that a search head and one or more indexers may perform during a search query. At block  402 , a search head receives a search query from a client. At block  404 , the search head analyzes the search query to determine what portion(s) of the query can be delegated to indexers and what portions of the query can be executed locally by the search head. At block  406 , the search head distributes the determined portions of the query to the appropriate indexers. In an embodiment, a search head cluster may take the place of an independent search head where each search head in the search head cluster coordinates with peer search heads in the search head cluster to schedule jobs, replicate search results, update configurations, fulfill search requests, etc. In an embodiment, the search head (or each search head) communicates with a master node (also known as a cluster master, not shown in Fig.) that provides the search head with a list of indexers to which the search head can distribute the determined portions of the query. The master node maintains a list of active indexers and can also designate which indexers may have responsibility for responding to queries over certain sets of events. A search head may communicate with the master node before the search head distributes queries to indexers to discover the addresses of active indexers. 
     At block  408 , the indexers to which the query was distributed, search data stores associated with them for events that are responsive to the query. To determine which events are responsive to the query, the indexer searches for events that match the criteria specified in the query. These criteria can include matching keywords or specific values for certain fields. The searching operations at block  408  may use the late-binding schema to extract values for specified fields from events at the time the query is processed. In an embodiment, one or more rules for extracting field values may be specified as part of a source type definition. The indexers may then either send the relevant events back to the search head, or use the events to determine a partial result, and send the partial result back to the search head. 
     At block  410 , the search head combines the partial results or events received from the indexers to produce a final result for the query. This final result may comprise different types of data depending on what the query requested. For example, the results can include a listing of matching events returned by the query, or some type of visualization of the data from the returned events. In another example, the final result can include one or more calculated values derived from the matching events. 
     The results generated by the system  108  can be returned to a client using different techniques. For example, one technique streams results or relevant events back to a client in real-time as they are identified. Another technique waits to report the results to the client until a complete set of results (which may include a set of relevant events or a result based on relevant events) is ready to return to the client. Yet another technique streams interim results or relevant events back to the client in real-time until a complete set of results is ready, and then returns the complete set of results to the client. In another technique, certain results are stored as “search jobs” and the client may retrieve the results by referring the search jobs. The search head can also perform various operations to make the search more efficient. For example, before the search head begins execution of a query, the search head can determine a time range for the query and a set of common keywords that all matching events include. The search head may then use these parameters to query the indexers to obtain a superset of the eventual results. Then, during a filtering stage, the search head can perform field-extraction operations on the superset to produce a reduced set of search results. This speeds up queries that are performed on a periodic basis. 
     2.7. Pipelined Search Language 
     Splunk Processing Language (SPL), used in conjunction with the SPLUNK® ENTERPRISE system, can be utilized to make a query. SPL is a pipelined search language in which a set of inputs is operated on by a first command in a command line, and then a subsequent command following the pipe symbol “|” operates on the results produced by the first command, and so on for additional commands. In other words, a search using SPL comprises a series of consecutive commands that are delimited by pipe (|) characters. The pipe character indicates to the system that the output or result of one command (to the left of the pipe) should be used as the input for the next command (to the right of the pipe). This enables the user to refine or enhance the data at each step along the pipeline until the desired results are attained. A search can start with search terms at the beginning of the pipeline. These search terms are keywords, phrases, Boolean expressions, key/value pairs, etc. that specify which events should be retrieved from the indices. The retrieved events can then be passed as inputs into a search command using a pipe character. The search commands comprise directives regarding what to do with the events after they have been retrieved from the index(es). For example, search commands may be used to filter unwanted information, extract more information, evaluate new fields, calculate statistics, reorder the results, create an alert, create a chart or perform some type of aggregate function, where an aggregate function can be used to return an aggregate value, e.g., an average value, a sum, a maximum value, a root mean square etc. 
     Accordingly, a pipeline search language is highly advantageous because it can perform “filtering” as well as “processing” functions. In other words, a single query can include search term expressions as well as data-analysis expressions. For example, search terms at the beginning of a query can perform a “filtering” step by retrieving a set of events based on a condition (e.g., records associated with server response times of less than 1 microsecond). The results of the filtering step can then be passed to a search command that performs a “processing” step (e.g. calculating an aggregate value related to the filtered events such as the average response time of servers with response times of less than 1 microsecond). Furthermore, the search term expressions allow events to be filtered by keyword as well as field value criteria. For example, a search can filter out all events containing the word “warning” or filter out all events where a field value associated with a field “clientip” is “10.0.1.2.” 
     The search results retrieved from the index in response to search terms at the beginning of a query can be considered of as a dynamically created table. Each search command redefines the shape of that table. Each indexed event can be considered a row with a column for each field value. Columns contain basic information about the data and also may contain data that has been dynamically extracted at search time. 
       FIG. 13  provides a visual representation of the manner in which a pipelined search language or query operates in accordance with the disclosed embodiments. The query  1310  is inputted by the user into the search bar  602 . The query comprises a search, the results of which are piped to two commands (namely, command  1  and command  2 ) that follow the search step. 
     Disk  1302  represents the event data in the raw record data store, e.g., similar to the event data illustrated in  FIG. 12 . 
     When a user query is processed, a search step will precede other queries in the pipeline in order to generate a set of events at block  1320 . For example, the query can comprise search terms “sourcetype=syslog ERROR” at the front of the pipeline as shown in  FIG. 13 . Intermediate results table  1304  shows fewer rows because it represents the subset of events retrieved from the index that matched the search terms “sourcetype=syslog ERROR” from search command  1310 . By way of further example, instead of a search step, the set of events at the head of the pipeline may be generated by a call to a pre-existing inverted index (as will be explained later). 
     At block  1322 , the set of events generated in the first part of the query may be piped to a query that searches the set of events for field-value pairs or for keywords. For example, the second intermediate results table  1306  shows fewer columns, representing the result of the top command, “top user” which summarizes the events into a list of the top 10 users and displays the user, count, and percentage. 
     Finally, at block  1324 , the results of the prior stage can be pipelined to another stage where further filtering or processing of the data can be performed, e.g., preparing the data for display purposes, filtering the data based on a condition, performing a mathematical calculation with the data, etc. As shown in  FIG. 13 , the “fields—percent” part of command  1310  removes the column that shows the percentage, thereby, leaving a final results table  1308  without a percentage column. In different embodiments, other query languages, such as the Structured Query Language (“SQL”), can be used to create a query. 
     2.8 Field Extraction Using a Configuration File 
     The search head  210  allows users to search and visualize event data extracted from raw machine data received from homogenous data sources. It also allows users to search and visualize event data extracted from raw machine data received from heterogeneous data sources. The search head  210  includes various mechanisms, which may additionally reside in an indexer  206 , for processing a query. 
     As mentioned above, the search system enables users to run queries against the stored data to retrieve events that meet criteria specified in a query, such as containing certain keywords or having specific values in defined fields.  FIG. 14  illustrates the manner in which keyword searches and field searches are processed in accordance with disclosed embodiments. 
     If a user inputs a search query into search bar  1401  that includes only keywords (also known as “tokens”), e.g., the keyword “error” or “warning”, the query search engine of the SPLUNK® ENTERPRISE system searches for those keywords directly in the event data  1412  stored in the raw record data store. Note that while  FIG. 14  only illustrates four events, the raw record data store (corresponding to data store  208  in  FIG. 2 ) may contain records for millions of events. 
     As disclosed above, an indexer can optionally generate a keyword index (not shown) to facilitate fast keyword searching for event data. The indexer includes the identified keywords in an index, which associates each stored keyword with reference pointers to events containing that keyword (or to locations within events where that keyword is located, other location identifiers, etc.). When an indexer subsequently receives a keyword-based query, the indexer can access the keyword index to quickly identify events containing the keyword. For example, if the keyword “HTTP” was indexed by the indexer at index time, and the user searches for the keyword “HTTP”, events  1403 ,  1404  and  1405  will be identified based on the results returned from the keyword index. As also noted above, the index contains reference pointers to the events containing the keyword, which allows for efficient retrieval of the relevant events from the raw record data store. 
     If a user searches for a keyword that has not been indexed by the indexer, the SPLUNK® ENTERPRISE system would nevertheless be able to retrieve the events by searching the event data for the keyword in the raw record data store  1412 , shown in  FIG. 14 , directly. For example, if a user searches for the keyword “frank”, and the name “frank” has not been indexed at index time, the SPLUNK® ENTERPRISE system will search the event data directly and return the first event  1403 . Note that whether the keyword has been indexed at index time or not, in both cases the raw data with the events  1412  is accessed from the raw data record store to service the keyword search. In the case where the keyword has been indexed, the index will contain a reference pointer that will allow for a more efficient retrieval of the event data from the data store. If the keyword has not been indexed, the search engine will need to search through all the records in the data store to service the search. 
     In most cases, however, in addition to keywords, a user&#39;s search will also include fields. The term “field” refers to a location in the event data containing one or more values for a specific data item. Often, a field is a value with a fixed, delimited position on a line, or a name and value pair, where there is a single value to each field name. A field can also be multivalued, that is, it can appear more than once in an event and have a different value for each appearance, e.g., email address fields. Fields are searchable name and value pairings that distinguish one event from another. Some examples of fields are “clientip” for IP addresses accessing a web server, or the “From” and “To” fields in email addresses. 
     By way of further example, consider the search, “status=404”. This search query finds events with “status” fields that have a value of “404.” When the search is run, the search engine does not look for events with any other “status” value. It also does not look for events containing other fields that share “404” as a value. As a result, the search returns a set of results that are more focused than if “404” had been used in the search string as part of a keyword search. Note also that fields can appear in events as “key=value” pairs such as “user name=Bob.” But in most cases, field values appear in fixed, delimited positions without identifying keys. For example, the data store may contain events where the “user name” value always appears by itself after the timestamp as illustrated by the following string: “November 15 09:33:22 johnryan.” 
     The SPLUNK® ENTERPRISE system advantageously allows for search time field extraction. In other words, fields can be extracted from the event data at search time using late-binding schema as opposed to at data ingestion time, which was a major limitation of the prior art systems. 
     In response to receiving the search query, search head  210  uses extraction rules to extract values for the fields associated with a field or fields in the event data being searched. The search head  210  obtains extraction rules that specify how to extract a value for certain fields from an event. Extraction rules can comprise regex rules that specify how to extract values for the relevant fields. In addition to specifying how to extract field values, the extraction rules may also include instructions for deriving a field value by performing a function on a character string or value retrieved by the extraction rule. For example, a transformation rule may truncate a character string, or convert the character string into a different data format. In some cases, the query itself can specify one or more extraction rules. 
       FIG. 14  illustrates the manner in which configuration files may be used to configure custom fields at search time in accordance with the disclosed embodiments. In response to receiving a search query, the SPLUNK® ENTERPRISE system determines if the query references a “field.” For example, a query may request a list of events where the “clientip” field equals “127.0.0.1.” If the query itself does not specify an extraction rule and if the field is not a metadata field, e.g., time, host, source, source type, etc., then in order to determine an extraction rule, the search engine may, in one or more embodiments, need to locate configuration file  1402  during the execution of the search as shown in  FIG. 14 . 
     Configuration file  1402  may contain extraction rules for all the various fields that are not metadata (or prior indexed) fields, e.g., the “clientip” field. The extraction rules may be inserted into the configuration file in a variety of ways. In some embodiments, the extraction rules can comprise regular expression rules that are manually entered in by the user. Regular expressions match patterns of characters in text and are used for extracting custom fields in text. 
     In one or more embodiments, as noted above, a field extractor may be configured to automatically generate extraction rules for certain field values in the events when the events are being created, indexed, or stored, or possibly at a later time. In one embodiment, a user may be able to dynamically create custom fields by highlighting portions of a sample event that should be extracted as fields using a graphical user interface. The system would then generate a regular expression, which extracts those fields from similar events, and store the regular expression as an extraction rule for the associated field in the configuration file  1402 . 
     In some embodiments, the indexers may automatically discover certain custom fields at index time and the regular expressions for those fields will be automatically generated at index time and stored as part of extraction rules in configuration file  1402 . For example, fields that appear in the event data as “key=value” pairs may be automatically extracted as part of an automatic field discovery process. Note that there may be several other ways of adding field definitions to configuration files in addition to the methods discussed herein. 
     The search head  210  can apply the extraction rules derived from configuration file  1402  to event data that it receives from indexers  206 . Indexers  206  may apply the extraction rules from the configuration file to events in an associated data store  208 . Extraction rules can be applied to all the events in a data store, or to a subset of the events that have been filtered based on some criteria (e.g., event time stamp values, etc.). Extraction rules can be used to extract one or more values for a field from events by parsing the event data and examining the event data for one or more patterns of characters, numbers, delimiters, etc., that indicate where the field begins and, optionally, ends. 
     In one more embodiments, the extraction rule in configuration file  1402  will also need to define the type or set of events that the rule applies to. Because the raw record data store will contain events from multiple heterogeneous sources, multiple events may contain the same fields in different locations because of discrepancies in the format of the data generated by the various sources. Furthermore, certain events may not contain a particular field at all. For example, event  1409  also contains “clientip” field, however, the “clientip” field occurs within a different format as compared with events  1403 - 1405 . To address the discrepancies in the format and content of the different types of events, the configuration file will also need to specify the set of events that an extraction rule applies to, e.g., extraction rule  1406  specifies a rule for filtering by the type of event and contains a regular expression for parsing out the field value. Accordingly, each extraction rule will pertain to only a particular type of event (e.g. to a particular sourcetype). If a particular field, e.g., “clientip” occurs in multiple events (e.g. events from multiple different sources), each of those types of events would need its own corresponding extraction rule in the configuration file  1402  and each of the extraction rules would comprise a different regular expression to parse out the associated field value. The most common way to categorize events is by source type because events generated by a particular source can have the same format. 
     It should be noted that fields and corresponding values may also be extracted using other fields. In other words, new fields can be defined by performing transformations and/or calculations with fields extracted from raw data. These fields can also be defined in the configuration file  1402 . 
     The field extraction rules stored in configuration file  1402  perform search-time field extractions. For example, for a query that requests a list of events with source type “access_combined” where the “clientip” field equals “127.0.0.1,” the query search engine would first locate the configuration file  1402  to retrieve extraction rule  1406  that would allow it to extract values associated with the “clientip” field from the event data  1410  where the source type is “access_combined.” After the “clientip” field has been extracted from all the events comprising the “clientip” field where the source type is “access_combined,” the query search engine can then execute the field criteria by performing the compare operation to filter out the events where the “clientip” field equals “127.0.0.1.” In the example shown in  FIG. 14 , events  1403 - 1405  would be returned in response to the user query. In this manner, the search engine can service queries containing field criteria in addition to queries containing keyword criteria (as explained above). 
     The configuration file can be created during indexing. It may either be manually created by the user or automatically generated with certain predetermined field extraction rules. As discussed above, the events may be distributed across several indexers, wherein each indexer may be responsible for storing and searching a subset of the events contained in a corresponding data store. In a distributed indexer system, each indexer would need to maintain a local copy of the configuration file that is synchronized periodically across the various indexers (as described in U.S. application Ser. No. 14/815,973, filed Aug. 1, 2015, entitled “GENERATING AND STORING SUMMARIZATION TABLES FOR SETS OF SEARCHABLE EVENTS” and in U.S. application Ser. No. 15/007,185, filed Jan. 26, 2016, entitled “GENERATING AND STORING SUMMARIZATION TABLES FOR SEARCHABLE EVENTS”, both of which are hereby incorporated by reference in their entirety for all purposes). 
     The ability to add schema to the configuration file at search time results in increased efficiency. A user can create new fields at search time and simply add field definitions to the configuration file. As a user learns more about the data in the events, the user can continue to refine the late-binding schema by adding new fields, deleting fields, or modifying the field extraction rules in the configuration file for use the next time the schema is used by the system. Because the SPLUNK® ENTERPRISE system maintains the underlying raw data and uses late-binding schema for searching the raw data, it enables a user to continue investigating and learn valuable insights about the raw data long after data ingestion time. 
     The ability to add multiple field definitions to the configuration file at search time also results in increased flexibility. For example, multiple field definitions can be added to the configuration file to capture the same field across events generated by different source types. This allows the SPLUNK® ENTERPRISE system to search and correlate data across heterogeneous sources flexibly and efficiently. 
     Further, by providing the field definitions for the queried fields at search time, the configuration file  1402  allows the record data store  1402  to be field searchable. In other words, the raw record data store  1402  can be searched using keywords as well as fields, wherein the fields are searchable name/value pairings that distinguish one event from another and can be defined in configuration file  1402  using extraction rules. In comparison to a search containing field names, a keyword search does not need the configuration file and can search the event data directly as shown in  FIG. 14 . 
     It should also be noted that any events filtered out by performing a search-time field extraction using a configuration file can be further processed by directing the results of the filtering step to a processing step using a pipelined search language. Using the prior example (requesting a list of events with source type “access_combined” where the “clientip” field equals “127.0.0.1), a user could pipeline the results of the compare step to an aggregate function by asking the query search engine to count the number of events where the “clientip” field equals “127.0.0.1.” 
     It should be noted that configuration files are not the only source for extraction rules. Configuration settings and configuration files will typically be used in connection with event records that are unstructured. Events can also be extracted from sources, e.g., csv files where the data is captured in a structured file format. Fields can be extracted from structured file formats, e.g., csv files, without requiring configuration settings. 
       FIG. 5  illustrates an example of raw machine data received from disparate data sources. In this example, a user submits an order for merchandise using a vendor&#39;s shopping application program  501  running on the user&#39;s system. In this example, the order was not delivered to the vendor&#39;s server due to a resource exception at the destination server that is detected by the middleware code  502 . The user then sends a message to the customer support  503  to complain about the order failing to complete. The three systems  501 ,  502 , and  503  are disparate systems that do not have a common logging format. The order application  501  sends log data  504  to the SPLUNK® ENTERPRISE system in one format, the middleware code  502  sends error log data  505  in a second format, and the support server  503  sends log data  506  in a third format. 
     Using the log data received at one or more indexers  206  from the three systems the vendor can uniquely obtain an insight into user activity, user experience, and system behavior. The search head  210  allows the vendor&#39;s administrator to search the log data from the three systems that one or more indexers  206  are responsible for searching, thereby obtaining correlated information, such as the order number and corresponding customer ID number of the person placing the order. The system also allows the administrator to see a visualization of related events via a user interface. The administrator can query the search head  210  for customer ID field value matches across the log data from the three systems that are stored at the one or more indexers  206 . The customer ID field value exists in the data gathered from the three systems, but the customer ID field value may be located in different areas of the data given differences in the architecture of the systems—there is a semantic relationship between the customer ID field values generated by the three systems. The search head  210  requests event data from the one or more indexers  206  to gather relevant event data from the three systems. It then applies extraction rules to the event data in order to extract field values that it can correlate. The search head may apply a different extraction rule to each set of events from each system when the event data format differs among systems. In this example, the user interface can display to the administrator the event data corresponding to the common customer ID field values  507 ,  508 , and  509 , thereby providing the administrator with insight into a customer&#39;s experience. 
     Note that query results can be returned to a client, a search head, or any other system component for further processing. In general, query results may include a set of one or more events, a set of one or more values obtained from the events, a subset of the values, statistics calculated based on the values, a report containing the values, or a visualization, such as a graph or chart, generated from the values. 
     2.9. Example Search Screen 
       FIG. 6A  illustrates an example search screen  600  in accordance with the disclosed embodiments. Search screen  600  includes a search bar  602  that accepts user input in the form of a search string. It also includes a time range picker  612  that enables the user to specify a time range for the search. The SPLUNK® ENTERPRISE system is adept at handling both real-time searches and historical searches. For “historical searches” the user can select a specific time range, or alternatively a relative time range, such as “today,” “yesterday” or “last week.” For “real-time searches,” the user can select the size of a preceding time window to search for real-time events. A “real-time” search can be open-ended, e.g., a query could request any events where the server response time is over 1 second in the last hour and further request that the search results continue to be updated. Search screen  600  also initially displays a “data summary” dialog as is illustrated in  FIG. 6B  that enables the user to select different sources for the event data, such as by selecting specific hosts and log files. 
     After the search is executed, the search screen  600  in  FIG. 6A  can display the results through search results tabs  604 , wherein search results tabs  604  includes: an “events tab” that displays various information about events returned by the search; a “statistics tab” that displays statistics about the search results; and a “visualization tab” that displays various visualizations of the search results. The events tab illustrated in  FIG. 6A  displays a timeline graph  605  that graphically illustrates the number of events that occurred in one-hour intervals over the selected time range. It also displays an events list  608  that enables a user to view the raw data in each of the returned events. It additionally displays a fields sidebar  606  that includes statistics about occurrences of specific fields in the returned events, including “selected fields” that are pre-selected by the user, and “interesting fields” that are automatically selected by the system based on pre-specified criteria. 
     2.10. Data Models 
     A data model is a hierarchically structured search-time mapping of semantic knowledge about one or more datasets. It encodes the domain knowledge necessary to build a variety of specialized searches of those datasets. Those searches, in turn, can be used to generate reports. 
     A data model is composed of one or more “objects” (or “data model objects”) that define or otherwise correspond to a specific set of data. 
     Objects in data models can be arranged hierarchically in parent/child relationships. Each child object represents a subset of the dataset covered by its parent object. The top-level objects in data models are collectively referred to as “root objects.” 
     Child objects have inheritance. Data model objects are defined by characteristics that mostly break down into constraints and attributes. Child objects inherit constraints and attributes from their parent objects and have additional constraints and attributes of their own. Child objects provide a way of filtering events from parent objects. Because a child object always provides an additional constraint in addition to the constraints it has inherited from its parent object, the dataset it represents is always a subset of the dataset that its parent represents. 
     For example, a first data model object may define a broad set of data pertaining to e-mail activity generally, and another data model object may define specific datasets within the broad dataset, such as a subset of the e-mail data pertaining specifically to e-mails sent. Examples of data models can include electronic mail, authentication, databases, intrusion detection, malware, application state, alerts, compute inventory, network sessions, network traffic, performance, audits, updates, vulnerabilities, etc. Data models and their objects can be designed by knowledge managers in an organization, and they can enable downstream users to quickly focus on a specific set of data. For example, a user can simply select an “e-mail activity” data model object to access a dataset relating to e-mails generally (e.g., sent or received), or select an “e-mails sent” data model object (or data sub-model object) to access a dataset relating to e-mails sent. 
     A data model object may be defined by (1) a set of search constraints, and (2) a set of fields. Thus, a data model object can be used to quickly search data to identify a set of events and to identify a set of fields to be associated with the set of events. For example, an “e-mails sent” data model object may specify a search for events relating to e-mails that have been sent, and specify a set of fields that are associated with the events. Thus, a user can retrieve and use the “e-mails sent” data model object to quickly search source data for events relating to sent e-mails, and may be provided with a listing of the set of fields relevant to the events in a user interface screen. 
     A child of the parent data model may be defined by a search (typically a narrower search) that produces a subset of the events that would be produced by the parent data model&#39;s search. The child&#39;s set of fields can include a subset of the set of fields of the parent data model or additional fields. Data model objects that reference the subsets can be arranged in a hierarchical manner, so that child subsets of events are proper subsets of their parents. A user iteratively applies a model development tool (not shown in Fig.) to prepare a query that defines a subset of events and assigns an object name to that subset. A child subset is created by further limiting a query that generated a parent subset. A late-binding schema of field extraction rules is associated with each object or subset in the data model. 
     Data definitions in associated schemas can be taken from the common information model (CIM) or can be devised for a particular schema and optionally added to the CIM. Child objects inherit fields from parents and can include fields not present in parents. A model developer can select fewer extraction rules than are available for the sources returned by the query that defines events belonging to a model. Selecting a limited set of extraction rules can be a tool for simplifying and focusing the data model, while allowing a user flexibility to explore the data subset. Development of a data model is further explained in U.S. Pat. Nos. 8,788,525 and 8,788,526, both entitled “DATA MODEL FOR MACHINE DATA FOR SEMANTIC SEARCH”, both issued on 22 Jul. 2014, U.S. Pat. No. 8,983,994, entitled “GENERATION OF A DATA MODEL FOR SEARCHING MACHINE DATA”, issued on 17 Mar. 2015, U.S. patent application Ser. No. 14/611,232, entitled “GENERATION OF A DATA MODEL APPLIED TO QUERIES”, filed on 31 Jan. 2015, and U.S. patent application Ser. No. 14/815,884, entitled “GENERATION OF A DATA MODEL APPLIED TO OBJECT QUERIES”, filed on 31 Jul. 2015, each of which is hereby incorporated by reference in its entirety for all purposes. See, also, Knowledge Manager Manual, Build a Data Model, Splunk Enterprise 6.1.3 pp. 150-204 (Aug. 25, 2014). 
     A data model can also include reports. One or more report formats can be associated with a particular data model and be made available to run against the data model. A user can use child objects to design reports with object datasets that already have extraneous data pre-filtered out. In an embodiment, the data intake and query system  108  provides the user with the ability to produce reports (e.g., a table, chart, visualization, etc.) without having to enter SPL, SQL, or other query language terms into a search screen. Data models are used as the basis for the search feature. 
     Data models may be selected in a report generation interface. The report generator supports drag-and-drop organization of fields to be summarized in a report. When a model is selected, the fields with available extraction rules are made available for use in the report. The user may refine or filter search results to produce more precise reports. The user may select some fields for organizing the report and select other fields for providing detail according to the report organization. For example, “region” and “salesperson” are fields used for organizing the report and sales data can be summarized (subtotaled and totaled) within this organization. The report generator allows the user to specify one or more fields within events and apply statistical analysis on values extracted from the specified one or more fields. The report generator may aggregate search results across sets of events and generate statistics based on aggregated search results. Building reports using the report generation interface is further explained in U.S. patent application Ser. No. 14/503,335, entitled “GENERATING REPORTS FROM UNSTRUCTURED DATA”, filed on 30 Sep. 2014, and which is hereby incorporated by reference in its entirety for all purposes, and in Pivot Manual, Splunk Enterprise 6.1.3 (Aug. 4, 2014). Data visualizations also can be generated in a variety of formats, by reference to the data model. Reports, data visualizations, and data model objects can be saved and associated with the data model for future use. The data model object may be used to perform searches of other data. 
       FIG. 7  illustrates a user interface screen where a user may select report generation options using data models. The report generation process may be driven by a predefined data model object, such as a data model object defined or saved via a reporting application or a data model object obtained from another source. A user can load a saved data model object using a report editor. For example, the initial search query and fields used to drive the report editor may be obtained from a data model object. The data model object that is used to drive a report generation process may define a search and a set of fields. Upon loading of the data model object, the report generation process may enable a user to use the fields (e.g., the fields defined by the data model object) to define criteria for a report (e.g., filters, split rows/columns, aggregates, etc.) and the search may be used to identify events (e.g., to identify events responsive to the search) used to generate the report. That is, for example, if a data model object is selected to drive a report editor, the graphical user interface of the report editor may enable a user to define reporting criteria for the report using the fields associated with the selected data model object, and the events used to generate the report may be constrained to the events that match, or otherwise satisfy, the search constraints of the selected data model object. 
     The selection of a data model object for use in driving a report generation may be facilitated by a data model object selection interface. 
     Once a data model object is selected by the user, a user interface screen  700  shown in  FIG. 7  may display an interactive listing of automatic field identification options  701  based on the selected data model object. For example, a user may select one of the three illustrated options (e.g., the “All Fields” option  702 , the “Selected Fields” option  703 , or the “Coverage” option (e.g., fields with at least a specified % of coverage)  704 ). If the user selects the “All Fields” option  702 , all of the fields identified from the events that were returned in response to an initial search query may be selected. That is, for example, all of the fields of the identified data model object fields may be selected. If the user selects the “Selected Fields” option  703 , only the fields from the fields of the identified data model object fields that are selected by the user may be used. If the user selects the “Coverage” option  704 , only the fields of the identified data model object fields meeting a specified coverage criteria may be selected. A percent coverage may refer to the percentage of events returned by the initial search query that a given field appears in. Thus, for example, if an object dataset includes 10,000 events returned in response to an initial search query, and the “avg_age” field appears in 854 of those 10,000 events, then the “avg_age” field would have a coverage of 8.54% for that object dataset. If, for example, the user selects the “Coverage” option and specifies a coverage value of 2%, only fields having a coverage value equal to or greater than 2% may be selected. The number of fields corresponding to each selectable option may be displayed in association with each option. For example, “97” displayed next to the “All Fields” option  702  indicates that 97 fields will be selected if the “All Fields” option is selected. The “3” displayed next to the “Selected Fields” option  703  indicates that 3 of the 97 fields will be selected if the “Selected Fields” option is selected. The “49” displayed next to the “Coverage” option  704  indicates that 49 of the 97 fields (e.g., the 49 fields having a coverage of 2% or greater) will be selected if the “Coverage” option is selected. The number of fields corresponding to the “Coverage” option may be dynamically updated based on the specified percent of coverage. 
     2.11. Acceleration Technique 
     The above-described system provides significant flexibility by enabling a user to analyze massive quantities of minimally processed data “on the fly” at search time instead of storing pre-specified portions of the data in a database at ingestion time. This flexibility enables a user to see valuable insights, correlate data, and perform subsequent queries to examine interesting aspects of the data that may not have been apparent at ingestion time. 
     However, performing extraction and analysis operations at search time can involve a large amount of data and require a large number of computational operations, which can cause delays in processing the queries. Advantageously, SPLUNK® ENTERPRISE system employs a number of unique acceleration techniques that have been developed to speed up analysis operations performed at search time. These techniques include: (1) performing search operations in parallel across multiple indexers; (2) using a keyword index; (3) using a high performance analytics store; and (4) accelerating the process of generating reports. These novel techniques are described in more detail below. Note that none of the acceleration techniques are mutually exclusive. They can all be used together in the same system contemporaneously. 
     2.11.1. Aggregation Technique 
     To facilitate faster query processing, a query can be structured such that multiple indexers perform the query in parallel, while aggregation of search results from the multiple indexers is performed locally at the search head. For example,  FIG. 8  illustrates how a search query  802  received from a client at a search head  210  can split into two phases, including: (1) subtasks  804  (e.g., data retrieval or simple filtering) that may be performed in parallel by indexers  206  for execution, and (2) a search results aggregation operation  806  to be executed by the search head when the results are ultimately collected from the indexers. 
     During operation, upon receiving search query  802 , a search head  210  determines that a portion of the operations involved with the search query may be performed locally by the search head. The search head also determined the portion of the operations that may be distributed to the indexers. Typically, most of the computationally intensive operations will be distributed to the indexers. The search head modifies search query  802  by substituting “stats” (create aggregate statistics over results sets received from the indexers at the search head) with “prestats” (create statistics by the indexer from local results set) to produce search query  804 , and then distributes search query  804  to distributed indexers, which are also referred to as “search peers.” The multiple indexers operate in parallel and each indexer operates on only a non-overlapping portion of the overall data. Note that search queries may generally specify search criteria or operations to be performed on events that meet the search criteria. Search queries may also specify field names, as well as search criteria for the values in the fields or operations to be performed on the values in the fields. Moreover, the search head may distribute the full search query to the search peers as illustrated in  FIG. 4 , or may alternatively distribute a modified version (e.g., a more restricted version) of the search query to the search peers. In this example, the indexers are responsible for producing the results and sending them to the search head. After the indexers return the results to the search head, the search head aggregates the received results  806  to form a single search result set. In this way, using map-reduce techniques allows each indexer to return partial responses for a subset of events to a search head that combines the results to produce an answer for the query. By executing the query in this manner, the system effectively distributes the computational operations across the indexers while minimizing data transfers. 
     2.11.2. Keyword Index 
     As described above with reference to the flow charts in  FIG. 3  and  FIG. 4 , data intake and query system  108  can construct and maintain one or more keyword indices to quickly identify events containing specific keywords. This technique can greatly speed up the processing of queries involving specific keywords. As mentioned above, to build a keyword index (also known an “tokenizing”), an indexer first identifies a set of keywords. Then, the indexer includes the identified keywords in an index, which associates each stored keyword with references to events containing that keyword, or to locations within events where that keyword is located. When an indexer subsequently receives a keyword-based query, the indexer can access the keyword index to quickly identify events containing the keyword. 
     2.11.3. High Performance Analytics Store 
     To speed up certain types of queries, e.g., frequently encountered queries or computationally intensive queries, some embodiments of system  108  create a high performance analytics store, which is referred to as a “summarization table,” (also referred to as a “lexicon” or “inverted index”) that contains entries for specific field-value pairs. Each of these entries keeps track of instances of a specific value in a specific field in the event data and includes references (or posting values) to events containing the specific value in the specific field. A reference value may be a pointer, memory address, etc. For example, an example entry in an inverted index can keep track of occurrences of the value “94107” in a “ZIP code” field of a set of events and the entry includes references to all of the events that contain the value “94107” in the ZIP code field. Creating the inverted index data structure avoids the computational overhead each time a query needs to be run on a frequently encountered field-value pair. In order to expedite queries, in some embodiments, the search engine will employ the inverted index separate from the raw record data store to generate responses to the received queries. In other embodiments, the search engine may employ the inverted index to leverage the posting values therein to provide faster and more efficient access to the raw event records. 
     Note that the term “summarization table” or “inverted index” as used herein is a data structure (stored in memory, e.g., in a file) that may be generated by an indexer that includes at least field names and field values that have been extracted and/or indexed from event records. An inverted index may also include reference values that point to the location(s) in the field searchable data store where the event records that include the field may be found. Also, an inverted index may be stored using well-know compression techniques to reduce its storage size. 
     Further, note that the term “reference value” (also referred to as a “posting value”) as used herein is a value that references the location of a source record in the field searchable data store. In some embodiments, the reference value may include additional information about each record, such as timestamps, record size, meta-data, or the like. Each reference value may be a unique identifier which may be used to access the event data directly in the field searchable data store. In some embodiments, the reference values may be ordered based on each event record&#39;s timestamp. For example, if numbers are used as identifiers, they may be sorted so event records having a later timestamp always have a lower valued identifier than event records with an earlier timestamp, or vice-versa. Reference values are often included in inverted indexes for retrieving and/or identifying event records efficiently. 
     In one or more embodiments, an inverted index is generated in response to a user-initiated collection query. The term “collection query” as used herein refers to queries that include commands that generate summarization information and inverted indexes (or summarization tables) from event records stored in the field searchable data store. 
     Note that a collection query is a special type of query that can be user-generated and is used to create an inverted index. A collection query is not the same as a query that is used to call up or invoke a pre-existing inverted index. In one or more embodiments, a query can comprise an initial step that calls up a pre-generated inverted index on which further filtering and processing can be performed. For example, referring back to  FIG. 13 , a set of events can be generated at block  1320  by either using a “collection” query to create a new inverted index or by calling up a pre-generated inverted index. A query with several pipelined steps will start with a pre-generated index to accelerate the query because creating a new inverted index using a “collection query” can have a high computational overhead. 
       FIG. 15  illustrates the manner in which an inverted index is created and used in accordance with the disclosed embodiments. As shown in  FIG. 15 , an inverted index  1502  can be created in response to a user-initiated collection query using the event data  1503  stored in the raw record data store. For example, a non-limiting example of a collection query may include “collect clientip=127.0.0.1” which may result in an inverted index  1502  being generated from the event data  1503  as shown in  FIG. 15 . It should be noted that the collection query may also specify other fields from the event data to index into the inverted index as well, e.g., the request line from the client  1206 , the status code returned by the server to the client  1207  (as explained in connection with  FIG. 12 ) etc. Stated differently, other fields from the event data besides “clientip” may also be indexed into the same summarization table. 
     Each entry in inverted index  1502  includes an event reference value that references the location of a source record in the field searchable data store. As mentioned above, the reference value may be used to access the original event record directly from the field searchable data store efficiently in subsequent searches. In other words, a subsequent search for instances where “clientip” equals “127.0.0.1” in the raw record data store can leverage the pre-created inverted index  1502  and the posting values therein to efficiently access the event data  1503  in the raw record data store to retrieve the relevant events instead of searching the entire data store. Using posting values in the inverted index to quickly access the relevant events (e.g., events with posting values 55000, 55002, 55005, and 55007 as shown in  FIG. 15 ), dramatically reduces the computational overhead as compared with searching for the desired field-value pair anew in the raw record data store. 
     Note that while inverted index  1502  is represented in  FIG. 15  as comprising a separate entry for each occurrence of a field value pair in the event records, the inverted index data structure is not limited to being represented as such in memory. For example, an inverted index may contain only one entry for each unique field value pair and all the reference values for that particular field value pair may be stored as part of a single entry (e.g. each entry may comprise multiple columns, wherein each column stores a separate reference value corresponding to each occurrence of the particular field value pair within the event records). In other embodiments, the information contained in an inverted index may be represented within a data structure in multiple different ways within memory. Inverted index  1502  provides just one example of a data structure for an inverted index. 
     In one or more embodiments, if one or more of the queries is a collection query, the responsive indexers may generate summarization information based on the fields of the event records located in the field searchable data store. In at least one of the various embodiments, one or more of the fields used in the summarization information may be listed in the collection query and/or they may be determined based on terms included in the collection query. For example, a collection query may include an explicit list of fields to summarize. Or, in at least one of the various embodiments, a collection query may include terms or expressions that explicitly define the fields, e.g., using regex rules. Referring back to the example in  FIG. 15 , prior to running the collection query that generates the inverted index  1502 , the field name “clientip” may need to be defined in a configuration file by specifying the “access_combined” source type and a regular expression rule to parse out the client IP address. Alternatively, the collection query may contain an explicit definition for the field name “clientip” which may obviate the need to reference the configuration file at search time. The field “clientip” may also be defined in a number of other ways including automated lookups. 
     In one or more embodiments, collection queries may be saved and scheduled to run periodically. These scheduled collection queries may periodically update the summarization information corresponding to the query. For example, if the collection query that generates inverted index  1502  is scheduled to run periodically, one or more indexers would periodically search through the relevant buckets to update inverted index  1502  with event data for any new events with the “clientip” value of “127.0.0.1.” 
     In some embodiments, the inverted indexes (e.g., inverted index  1502 ) that include fields, values, and reference values (or posting value) for event records may be included in the summarization information provided to the user. In other embodiments, a user may not be interested in specific fields and values contained in the inverted index, but may need to perform a statistical query on the data in the inverted index. For example, referencing the example of  FIG. 15 , rather than viewing the fields within summarization table  1502 , a user&#39;s query may request generating a count of all client requests from IP address “127.0.0.1.” In this case, the search engine would simply return a result of “4” rather than including details about the inverted index  1502  in the information provided to the user. In other words, statistical or aggregate functions may be performed using the data summarized in the inverted index. 
     The pipelined search language, e.g., SPL of the SPLUNK® ENTERPRISE system can be used to pipe the contents of an inverted index to a statistical query using the “stats” command for example. A “stats” query refers to queries that generate result sets that may produce aggregate and statistical results from event records, e.g., average, mean, max, min, rms, etc. Where sufficient information is available in an inverted index, a “stats” query may generate their result sets rapidly from the summarization information available in the inverted index rather than directly scanning event records. For example, the contents of inverted index  1502  can be pipelined to a stats query, e.g., a “count” function that counts the number of entries in the inverted index and returns a value of “4.” In this way, inverted indexes may enable various stats queries to be performed without scanning or searching the event records. Accordingly, this optimization technique enables the system to quickly process queries that, for example, seek to determine how many events have a particular value for a particular field. To this end, the system can examine the entry in the inverted index to count instances of the specific value in the field without having to go through the individual events or perform data extractions at search time. 
     In some embodiments, the system maintains a separate inverted index for each of the above-described time-specific buckets that stores events for a specific time range. A bucket-specific inverted index includes entries for specific field-value combinations that occur in events in the specific bucket. Alternatively, the system can maintain a separate inverted index for each indexer. The indexer-specific inverted index includes entries for the events in a data store that are managed by the specific indexer. Indexer-specific inverted indexes may also be bucket-specific. In at least one or more embodiments, if one or more of the queries is a stats query, each indexer may generate a partial result set from previously generated summarization information. The partial result sets may be returned to the search head that received the query and combined into a single result set for the query 
     As mentioned above, the inverted index can be populated by running a periodic query that scans a set of events to find instances of a specific field-value combination, or alternatively instances of all field-value combinations for a specific field. A periodic query can be initiated by a user, or can be scheduled to occur automatically at specific time intervals. A periodic query can also be automatically launched in response to a query that asks for a specific field-value combination. In some embodiments, if summarization information is absent from an indexer that includes responsive event records, further actions may be taken, such as, the summarization information may be generated on the fly, warnings may be provided the user, the collection query operation may be halted, the absence of summarization information may be ignored, or the like, or combinations thereof. 
     In one or more embodiments, an inverted index may be set up to update continually. For example, the query may ask for the inverted index to update its result periodically, e.g., every hour. In such instances, the inverted index may be a dynamic data structure that is regularly updated to include information regarding incoming events. 
     In some cases, e.g., where a query is executed before an inverted index updates, when the inverted index may not cover all of the events that are relevant to a query, the system can use the inverted index to obtain partial results for the events that are covered by the inverted index, but may also have to search through other events that are not covered by the inverted index to produce additional results on the fly. In other words, an indexer would need to search through event data on the data store to supplement the partial results. These additional results can then be combined with the partial results to produce a final set of results for the query. Note that in typical instances where an inverted index is not completely up to date, the number of events that an indexer would need to search through to supplement the results from the inverted index would be relatively small. In other words, the search to get the most recent results can be quick and efficient because only a small number of event records will be searched through to supplement the information from the inverted index. The inverted index and associated techniques are described in more detail in U.S. Pat. No. 8,682,925, entitled “DISTRIBUTED HIGH PERFORMANCE ANALYTICS STORE”, issued on 25 Mar. 2014, U.S. Pat. No. 9,128,985, entitled “SUPPLEMENTING A HIGH PERFORMANCE ANALYTICS STORE WITH EVALUATION OF INDIVIDUAL EVENTS TO RESPOND TO AN EVENT QUERY”, filed on 31 Jan. 2014, and U.S. patent application Ser. No. 14/815,973, entitled “STORAGE MEDIUM AND CONTROL DEVICE”, filed on 21 Feb. 2014, each of which is hereby incorporated by reference in its entirety. 
     2.11.3.1 Using Reference Values in an Inverted Index to Retrieve and Extract Further Information From Associated Event Data 
     In one or more embodiments, if the system needs to process events that have a specific field-value combination, the system can use the references in the inverted index entry to directly access the events to extract further information without having to search all of the events to find the specific field-value combination at search time. In other words, the system can use the reference values to locate the associated event data in the field searchable data store and extract further information from those events, e.g., extract further field values from the events for purposes of filtering or processing or both. 
     The information extracted from the event data using the reference values can be directed for further filtering or processing in a query using the pipeline search language. The pipelined search language will, in one embodiment, include syntax that can direct the initial filtering step in a query to an inverted index. In one embodiment, a user would include syntax in the query that explicitly directs the initial searching or filtering step to the inverted index. 
     Referencing the example in  FIG. 15 , if the user determines that she needs the user id fields associated with the client requests from IP address “127.0.0.1” instead of incurring the computational overhead of performing a brand new search or re-generating the inverted index with an additional field “user id,” the user can instead generate a query that explicitly directs or pipes the contents of the pre-generated inverted index  1502  to another filtering step. The additional filtering step may, for example, use the posting values in inverted index  1502  to access related event records  1503  to extract the further information pertaining to the “user id” field. 
     For example, the additional filtering step may, for example, request the user ids for entries in inverted index  1502  where the server response time is greater than “0.0900” microseconds. The search engine would use the reference values stored in inverted index  1502  to retrieve the event data from the field searchable data store, filter the results based on the “response time” field values and, further, extract the user id field from the resulting event data to return to the user. There are only two events ( 1511  and  1513 ) within the event records  1503  where the server response time is greater than “0.0900” microseconds. Accordingly, in the present instance, the user ids “frank” and “carlos” would be returned to the user from the generated results table  1504 . 
     In one embodiment, the same methodology can be used to pipe the contents of the inverted index to a processing step. In other words, the user is able to use the inverted index to efficiently and quickly perform aggregate functions on field values that were not part of the initially generated inverted index. For example, a user may want to determine an average object size (size of the requested gif) requested by clients from IP address “127.0.0.1.” In this case, the search engine would again use the reference values stored in inverted index  1502  to retrieve the event data from the field searchable data store and, further, extract the object size field values from the associated events  1511 ,  1512 ,  1513  and  1514 . Once, the corresponding object sizes have been extracted (i.e. 2326, 2900, 2920, and 5000), the average can be computed and returned to the user. 
     In one embodiment, instead of explicitly invoking the inverted index in a user-generated query, e.g., by the use of special commands or syntax, the SPLUNK® ENTERPRISE system can be configured to automatically determine if any prior-generated inverted index can be used to expedite a user query. For example, the user&#39;s query may request the average object size (size of the requested gif) requested by clients from IP address “127.0.0.1.” without any reference to or use of inverted index  1502 . The search engine, in this case, would automatically determine that an inverted index  1502  already exists in the system that could expedite this query. In one embodiment, prior to running any search comprising a field-value pair, for example, a search engine may search though all the existing inverted indexes to determine if a pre-generated inverted index could be used to expedite the search comprising the field-value pair. Accordingly, the search engine would automatically use the pre-generated inverted index, e.g., index  1502  to generate the results without any user-involvement that directs the use of the index. 
     Using the reference values in an inverted index to be able to directly access the event data in the field searchable data store and extract further information from the associated event data for further filtering and processing is highly advantageous because it avoids incurring the computation overhead of regenerating the inverted index with additional fields or performing a new search. 
     As explained above, the SPLUNK® ENTERPRISE system includes one or more forwarders that receive raw machine data from a variety of input data sources, and one or more indexers that process and store the data in one or more data stores. By distributing events among the indexers and data stores, the indexers can analyze events for a query in parallel. In one or more embodiments, a multiple indexer implementation of the search system would maintain a separate and respective inverted index for each of the above-described time-specific buckets that stores events for a specific time range. A bucket-specific inverted index includes entries for specific field-value combinations that occur in events in the specific bucket. As explained above, a search head would be able to correlate and synthesize data from across the various buckets and indexers. 
     This feature advantageously expedites searches because instead of performing a computationally intensive search in a centrally located inverted index that catalogues all the relevant events, an indexer is able to directly search an inverted index stored in a bucket associated with the time-range specified in the query. This allows the search to be performed in parallel across the various indexers. Further, if the query requests further filtering or processing to be conducted on the event data referenced by the locally stored bucket-specific inverted index, the indexer is able to simply access the event records stored in the associated bucket for further filtering and processing instead of needing to access a central repository of event records, which would dramatically add to the computational overhead. 
     In one embodiment, there may be multiple buckets associated with the time-range specified in a query. If the query is directed to an inverted index, or if the search engine automatically determines that using an inverted index would expedite the processing of the query, the indexers will search through each of the inverted indexes associated with the buckets for the specified time-range. This feature allows the High Performance Analytics Store to be scaled easily. 
     In certain instances, where a query is executed before a bucket-specific inverted index updates, when the bucket-specific inverted index may not cover all of the events that are relevant to a query, the system can use the bucket-specific inverted index to obtain partial results for the events that are covered by a bucket-specific inverted index, but may also have to search through the event data in the bucket associated with the bucket-specific inverted index to produce additional results on the fly. In other words, an indexer would need to search through event data stored in the bucket (that was not yet processed by the indexer for the corresponding inverted index) to supplement the partial results from the bucket-specific inverted index. 
       FIG. 16  presents a flowchart illustrating how an inverted index in a pipelined search query can be used to determine a set of event data that can be further processed in accordance with the disclosed embodiments. 
     At block  1602 , a user generated query is inputted into the search bar  602 . The search interface also includes a time range picker  612  that enables the user to specify a time range for the search. 
     At block  1604 , an inverted index is retrieved. Note, that the inverted index can be retrieved in response to an explicit user search command inputted as part of the user generated query. Alternatively, the search engine can be configured to automatically use an inverted index if it determines that using the inverted index would expedite the servicing of the user generated query. Each of the entries in an inverted index keeps track of instances of a specific value in a specific field in the event data and includes references to events containing the specific value in the specific field. In order to expedite queries, in most embodiments, the search engine will employ the inverted index separate from the raw record data store to generate responses to the received queries. 
     At block  1606 , the query engine determines if the query contains further filtering and processing steps. If the query contains no further commands, then, in one embodiment, summarization information can be provided to the user at block  1614 . 
     If, however, the query does contain further filtering and processing commands, then at block  1610 , the query engine determines if the commands relate to further filtering or processing of the data extracted as part of the inverted index or whether the commands are directed to using the inverted index as an initial filtering step to further filter and process event data referenced by the entries in the inverted index. If the query can be completed using data already in the generated inverted index, then the further filtering or processing steps, e.g., a “count” number of records function, “average” number of records per hour etc. are performed and the results are provided to the user at block  1612 . 
     If, however, the query references fields that are not extracted in the inverted index, then the indexers will access event data pointed to by the reference values in the inverted index to retrieve any further information required at block  1616 . Subsequently, any further filtering or processing steps are performed on the fields extracted directly from the event data and the results are provided to the user at step  1618 . 
     2.11.3.2 Leveraging Reference Values in an Inverted Index to Retrieve Associated Event Data 
       FIG. 17  illustrates the manner in which an inverted index may be used to retrieve related event records efficiently in response to a query in accordance with the disclosed embodiments. As noted previously, reference values in a pre-generated inverted index may be leveraged to directly and efficiently access related event records without needing to search the entire raw record data store. In some instances, instead of performing a statistical or aggregate function using the summarized fields in the inverted index or using the associated event data in the record data store, the reference values in an inverted index may be leveraged to retrieve the entire related event records (including the raw data) for the user, e.g., to display on-screen for a user to review or to perform a further search on the retrieved event record. 
     Referencing the example in  FIG. 17 , a summarization table  1702  (generated previously using a collection query or otherwise) may contain summarization information for event records  1703  in a raw record data store where the “source” of the event records is an “error.log”. Stated differently, the summarization table summarizes all event records where the value of the “source” field is equal to “error.log.” Additionally, inverted index  1702  further comprises “clientip” as an additional field-value pair that is extracted into the summary information from events in the raw record store where “source” is equal to “error.log.” In other words, “clientip” is an indexed field that is also summarized in summarization table  1702 . 
     In response to receiving a user query that requests all event records where “source” equals “error.log,” posting values in the inverted index may be used to efficiently access and retrieve all event records that contain the matching field-value pair. Instead of searching for the field-value pair combination through potentially millions of event records in the data store, the search engine can leverage the posting values in the inverted index  1702  to directly access event records where the “source” field is equal to “error.log.” In the example of  FIG. 17 , posting values 550003 and 550006 are used to directly retrieve the associated event records  1713  and  1714 . 
     The retrieved event records  1720  may be displayed on-screen to the user for review or logged into a file of the user&#39;s choice. In one embodiment, the entire event record, comprising all the indexed metadata fields (e.g., source, host, source type, etc.) and the raw data in the event, are displayed to the user as shown in  FIG. 17 . In another embodiment, the event records may be edited prior to displaying in accordance with the user instructions, e.g., the user may simply want to display the raw data in the event without the additional metadata fields. 
     In one embodiment, summarization table  1702  may also be leveraged to expedite certain types of searches. For example, if a search references a field that is already indexed in the summarization table, the summarization table  1702  can be used to execute the search faster. For example, in response to a search query where the user requests to retrieve all events where the “clientip” equals “127.10.1.1.015” and the “source” is an error log, the indexed field “clientip” in the summarization table  1702  can be leveraged to first determine all events where “clientip” equals “127.10.1.1.015.” After the query engine identifies only a single record  1798  in summarization table  1702  that satisfies the search criteria, the associated event record can be retrieved from the record data store  1703  using posting value 55,0003. 
     In one embodiment, in addition to retrieving entire associated event records, search time field extraction may be performed for certain fields within the events for a user. For example, if the user wants certain fields extracted from the events at search time (for purposes of “annotating” the retrieved events), the search time extraction of the fields may be performed while the events are being read or retrieved from the record data store. In other words, “annotating” the event records comprises performing search time field and field value extraction for the retrieved events. In one embodiment, even fields that have previously been indexed as part of the summarization table (e.g., clientip) may be directly extracted at search time from the retrieved event data  1720 . In other words, the summarization table may primarily be used for its posting values in order to provide faster access to the relevant event data; any field extraction from the event data (including field extraction for fields previously indexed in the summarization table) is conducted directly using the retrieved event data. As discussed in detail above, the rules for field extraction may be obtained through various sources, e.g., configuration files, etc. 
     In a different embodiment, however, the fields of interest and corresponding values may be derived from the summarization table if they are indexed with the summarization table, e.g., the field “clientip” and corresponding values may be extracted from the summarization table while any other fields that were not indexed in the summarization table will be extracted using the retrieved event data at search time. 
     In one embodiment, as discussed above, the user&#39;s query may pipe the retrieved event records to further filtering or processing steps using the pipelined search language. For example, a first portion of a user query may retrieve event records by leveraging an inverted index, while subsequent stages of the query may direct the retrieved event records for further processing or filtering. 
     Using the example in  FIG. 17 , a user&#39;s query may search for “requested file=furby.gif” in all events extracted from an error log (e.g. where the “source” field equals “error.log”). (Note that the requested file that resulted in an error in record  1714  is “daffy_duck.gif” while the requested file in record  1713  is “furby.gif”). Because “requested file” is not a field that has been indexed into summarization table  1798 , the predicate “requested file=furby.gif” cannot be evaluated using the summarization table. Accordingly, all the events extracted from error logs (e.g. events  1714  and  1713 ) need to be retrieved from the data store using the posting values in summarization table  1702  in order to evaluate the predicate. 
     The query engine may, in the first stage, leverage the inverted index  1702  to first efficiently retrieve those events where “source” field equals “error.log,” e.g., events  1720  in  FIG. 17 . Subsequently, the results from the first stage of the query may be piped to a subsequent stage where the retrieved events are filtered further using the predicate “requested file=furby.gif.” In response to evaluating the predicate, event record  1713  is retrieved. In addition to filtering, the event records retrieved using the reference values in the inverted index  1702  may also be piped to subsequent pipe-stages for further processing of the event data. For example, statistical calculations may be performed on the fields in the retrieved events to provide a response to the user. 
     In one embodiment, the user may explicitly invoke the inverted index  1702  in a first part of the query. Alternatively, as mentioned previously, even if the inverted index is not invoked, in a user-generated query, e.g., by the use of special commands or syntax, the SPLUNK® ENTERPRISE system can be configured to automatically determine if any prior-generated inverted index can be used to expedite a user query. For example, the user&#39;s query may request to search for “clientip=127.10.1.1.03” in all error logs. The SPLUNK® ENTERPRISE system may be configured, in such an instance, to search through all pre-existing inverted indices to determine if a pre-generated inverted index could be used to expedite the search comprising the field-value pair. Accordingly, the search engine would automatically use the pre-generated inverted index, e.g., index  1702  to generate the results without any user-involvement that directs the use of the index. 
     Using the reference values in an inverted index to be able to directly retrieve the event records from the field searchable data store is highly advantageous because it avoids incurring the computational overhead of performing a search through the entire raw record data store. The reference values are used as pointers to directly access and retrieve the event records with minimal processing overhead. The retrieved events are then displayed and annotated with certain fields for a user to review. 
       FIG. 18  presents a flowchart illustrating how an inverted index may be used to retrieve related event records efficiently in response to a query in accordance with the disclosed embodiments. 
     At block  1802 , a user generated query is inputted into the search bar  602 . 
     At block  1804 , an inverted index is retrieved. Note, that the inverted index can be retrieved in response to an explicit user search command inputted as part of the user generated query. Alternatively, the search engine can be configured to automatically use an inverted index if it determines that using the inverted index would expedite the servicing of the user-generated query. In other words, the search engine may be configured to determine if an inverted index exists that may expedite the user&#39;s query and further configured to use the inverted index if it exists. Each of the entries in an inverted index keeps track of instances of a specific value in a specific field in the event data and includes references to events containing the specific value in the specific field. In order to expedite queries, in most embodiments, the search engine will employ the inverted index and the reference values therein to access and retrieve the associated event records to generate responses to the received queries. 
     At block  1806 , the query engine uses the reference values in the inverted index to retrieve the referenced event records. It should be noted that in some embodiments the entire event record is retrieved and displayed to the user. Alternatively, in other embodiments, the event record retrieved may be displayed in accordance with a user&#39;s instructions, e.g., displaying only the raw data without the metadata fields. As noted above, in certain embodiments, search time field extraction or annotation for certain fields within the events may be performed when the referenced event records are retrieved. 
     At step  1810 , the query engine determines if the query contains further filtering and processing steps. If the query contains no further steps, then, in one embodiment, the retrieved event records along with any annotated fields can be presented to the user at step  1814 . 
     If, however, the query does contain further filtering and processing steps, then at block  1812 , the query engine performs the filtering and processing steps on the retrieved event data. For example, as noted above, a search predicate may require searching for “requested file=furby.gif” in all error logs. In order to satisfy the predicate, the retrieved event records  1720  may need to be further filtered. 
     At step  1816 , the results of the subsequent pipelined steps are displayed to the user. 
     2.11.3.3 Accelerating Data Models Using Inverted Indexes 
     In some embodiments, a summarization table can be generated for a data model and can be used, for example, to accelerate generation of reports on attributes (also referred to as “fields”) of a data model. As described previously, a data model can include one or more “objects” (also referred to as “data model objects”) that define or otherwise correspond to a specific set of data. A data model object may be defined by: (1) a set of search constraints; and (2) a set of structured fields. Thus, a data model object can be used to quickly search data to identify a set of events (e.g., a set of events that satisfy the set of search constraints of the data model object) and a set of structured fields associated with the set of events (e.g., the set of fields of the data model object that are in the set of events identified). Note, that “structured” fields are fields that are specifically defined as part the data model object definition by a creator of the data model. By comparison, “unstructured” fields (also referred to as ‘dynamic’ fields) may be fields that appear in the set of events that satisfy the set of search constraints of the data model object, but were not defined explicitly within the data model object definition. 
     For example, an “e-mails processed” data model object may specify a search for events relating to e-mails that have been processed by a given e-mail server, and specify a set of structured fields (e.g., date, size, etc.) that are associated with the events. Thus, a user can retrieve and use the “e-mails processed” data model object to quickly retrieve a listing of the set of structured fields (e.g., date, size, etc.) of the events relating to e-mails processed by the given e-mail server. By using a data model, the user may not have to recreate the search and re-identify the structured fields of interest. 
     Data model searches can be accelerated using summarization tables. Generating reports on very large datasets within data models can take significant amounts of time and can be impractical. Running reports on such large datasets regularly is impractical and the impracticality increases exponentially as more and more users in an organization run similar reports. Accordingly, data model acceleration may be employed using summarization tables. Data model acceleration accelerates all the structured fields defined in the data model. Data model acceleration uses the high performance analytics store (HPAS) by building summarization tables alongside the buckets containing raw event data in the indexers. Once data model acceleration is enabled, the SPLUNK® ENTERPRISE system starts building a summarization table that spans either the entire set of events in a data model or a user-indicated range. When the summarization table completes, any report that uses an accelerated data model dataset will execute leveraging the posting values in the summarization table rather than searching the full array of raw events whenever possible, and search time is improved significantly. These summarization tables can be stored in files and are accessed automatically when an event-based search is run on the data model to accelerate the search. In other words, if the user has chosen to accelerate the data model, the summarization tables will be leveraged automatically to execute event-based searches being run against the data model faster. 
     A data model summarization table for a data model can include or otherwise identify values for the structured fields (or attributes) specified by the data model that are from the events that satisfy the search criteria of the data model. For example, if a data model object specifies (1) search criteria of events from e-mail servers, and (2) a structured field of “size”, and a bucket includes 10,000 events total, with 1,000 of the 10,000 events having been generated by an e-mail server and including a structured field for size, then the data model summarization table may include or otherwise identify the 1,000 events and/or the values of the “size” fields of the 1,000 events. Further, the summarization table may include reference or posting values indicating the location of the 1,000 events pertaining to the email-server within the total set of 10,000 events. Thus, the set of data associated with the data model summarization table may be significantly smaller in size than the original set of data that is summarized. 
     The posting values in the summarization table are leveraged to easily access the relevant set of events within the raw record data store. In other words, a search of a data model dataset may be accelerated by using the posting values in the summarization table to easily access and retrieve the events associated with the data model dataset from the raw record data store. In the example cited above, to perform searches on the data model comprising the 1,000 events generated by the e-mail server, the reference values in the summarization table associated with the data model may be leveraged to easily access the 1,000 events rather than searching the entirety of the 10,000 events from the raw record data store each time. 
       FIG. 19A  illustrates a set of event records that may be stored in a bucket data structure comprised within a raw record data store in accordance with the disclosed embodiments. It should be noted that while the bucket may contain thousands of event records, for the purposes of this example only five event records  1902 ,  1904 ,  1906 ,  1908  and  1910  are illustrated. Event records  1902 ,  1904 ,  1906  and  1910  are extracted from an access log and are of the type “access_combined” while event  1908  is derived from an error log and is of the type “apache_error.” 
       FIG. 19B  illustrates a data model created by specifying search constraints for the events in  FIG. 19A  and accelerating the data model using a summarization table in accordance with the disclosed embodiments. By way of example, a user may want to define a data model object that specifies (1) search criteria of events of the “access_combined” type; (2) structured fields of “clientip” and “user id”. If the data model is accelerated, a summarization table  1924  is created that contains posting values for the 4 events (out of a total of 5 events in  FIG. 19A ) of the type “access_combined” and further comprises structured indexed fields, “clientip” and “user id.” Furthermore, the summarization table  1924  will also comprise posting values (e.g., 55000, 55001, 55002, 55004) that point directly to, or otherwise indicate, the location in the bucket within the raw record store where the associated event data is stored, as shown in  FIG. 19B . As noted previously, the posting values in the summarization table are leveraged to easily access the relevant set of events within the raw record data store so that the search engine does not have to search the entire raw record data store for events of the type “access_combined.” 
     In order to retrieve the events in the “access_combined” data model and to annotate them with structured fields within the model, an exemplary query  1925  that a user may enter through the query interface is “|datamodel&lt;name of datamodel&gt;search.” For example, assuming the name selected for the data model of  FIG. 19B  is “access_combined_events,” the exemplary query “|datamodel access_combined_events search” will run a search associated with the “access_combined_events” data model object. The command will retrieve events associated with the data model object and annotate the events with the structured fields. It should be noted that query  1925  shown in  FIG. 19B  is exemplary and that there may be other commands (e.g., the “from” command) that can also be used to retrieve event data from a data model dataset. 
     In response to query  1925 , the search engine will use the posting values in summarization table  1924  to locate and retrieve the events  1922  associated with the data model. The summarization table may primarily be used for its posting values in order to provide faster access to the relevant event data; any field extraction from the event data (including field extraction for structured fields previously indexed in the summarization table) is conducted directly using the retrieved event data. Because query  1925  does not comprise any further processing or filtering steps, the events  1922  will be retrieved and displayed through the user interface for a user to review. 
     Further, the event data may be annotated with the structured fields  1923  that are defined within the data model while the event data is being retrieved from the record data store. As mentioned above, in one embodiment, in addition to retrieving the associated event records, search time field extraction may be performed for structured fields within the events for a user. In one embodiment, the retrieved event records are annotated with the structured fields within the data model object (e.g., “clientip” field  1927  and “user id” field  1928 ) as the events are being read or retrieved from the record data store. 
     It should be noted that even though the “clientip” and “user id” fields are previously indexed fields (e.g., as shown in columns  1931  and  1932 ) and their values may be stored as part of summarization table  1924 , in typical embodiments, the structured fields are extracted directly from the raw event records  1922  at search time as the events are being read or retrieved using field extraction rules. As explained previously, field extraction rules can be derived from several different sources including configuration settings in configuration files. 
     Alternatively, in other embodiments, event data may be annotated with structured fields and corresponding values extracted from the summarization table  1924  instead of directly from the event records at search time, e.g., the field “clientip” and corresponding values may be extracted from the summarization table. The structured fields can, therefore, be annotated using data extracted from the summarization table  1924 , as opposed to the raw event records  1922 . 
     In some embodiments, the structured fields may be displayed with some statistical information regarding the values of the structured fields. For example, as shown in  FIG. 19B , information regarding the number of unique values taken on by each of the structured fields is provided. For example, there are at least  3  unique values for the “clientip” field within event data  1922  and there are four different user ids (e.g., frank, bob, carlos and virgil). In addition to the number of unique values, other statistics pertaining to a respective field may also be provided, e.g. the percentage of time each value appears, the percentage of times the field was found in all events, the number of events with the field, top values by time, maximum value over time, minimum value over time, rare values, etc. 
       FIG. 19C  illustrates the manner in which a query invoking the accelerated data model of  FIG. 19B  and comprising a predicate with a structured field may be processed in accordance with the disclosed embodiments. 
     As noted previously, data model searches using summarization tables are expedited significantly by using posting values as references to directly access the events comprised within the data model in the raw record data store. Furthermore, the query engine may comprise an optimizer that includes functionality to optimize the command pipeline. The command pipeline may be optimized, for example, to process a predicate in a search query that invokes a data model in the most efficient manner. 
     As noted previously, Splunk Processing Language (SPL) is a pipelined search language. The command pipeline in SPL is a sequence of commands, whereby each command is in a particular order. Each command in the sequence is ordered such that the output of a previous command is an input to the next command. For example, the output of the immediately preceding command may be the input to the immediate next commend. The particular order is preset prior to execution. Thus, the order of the commands in the sequence is independent of the execution. 
     The optimizer is able to, among other things, optimize the order of the commands in the sequence in order to execute the query more efficiently. Further, the optimizer may also include functionality to change the parameters of a command, add additional parameters to a command, remove a command, reorder commands and perform other actions so as to reduce an execution time of the pipeline on a computing system. 
     When a query is first received, the optimizer receives the initial command pipeline and partitions the pipeline into blocks corresponding to commands. The optimizer extracts the commands from the pipeline while maintaining the arguments of the commands. Subsequently, for each command in the sequence of commands semantic information is obtained. The optimizer may then generate an abstract semantic tree (AST) with the semantic information. 
     Using the AST, various types of optimization are performed. One example of an optimization is a predicate pushdown. For example, predicate pushdown is an optimization that applies predicates as early as possible in the pipeline, thereby avoiding searching and loading events that are not applicable. By performing predicate pushdown, the indexers may eliminate or reduce the number of events in the data stores that are searched. 
     Referencing the example in  FIG. 19C , if the user enters exemplary query  1945  into the query interface, the optimizer in the query engine will generate an AST for the query and determine whether the predicate “search user_id=frank” can be pushed down. 
     In the typical case, without a predicate pushdown, evaluating query  1945  comprises using summarization table  1945  to first retrieve all the events in the data model (e.g. the events  1922  shown in  FIG. 19B ) in response to the “|datamodel” search. Subsequently, the predicate “search user_id=frank” is evaluated against all the events retrieved from the first part of the pipeline. Stated differently, all four of the events  1922  returned in response to the first portion of the query are scanned to find events where the user_id=frank. 
     With the predicate pushdown, however, the query is resolved more efficiently. The predicate “search user_id=frank” is applied as early as possible in the pipeline. In other words, the predicate is applied prior to the “|datamodel” search portion of the query. In this case, using the indexed fields in the summarization table  1945 , the query engine can determine that there is only one event  1984  where the “user id” is equal to “frank.” Subsequently, when the remaining portion of the query is evaluated, only a single event  1946  with reference value 55,000 needs to be scanned and retrieved from the record data store. This event is retrieved using the corresponding posting value 55,000 in the summarization table  1945 . Accordingly, pushing the predicate allows a single event to be scanned and retrieved from the raw record data store (instead of all 4 events). 
     As discussed previously, the user interface may display event  1946  and annotate it with search time extracted structured fields  1947 , namely, “client ip” and “user id.” Similar to the example of  FIG. 19B , as shown in  FIG. 19C , information regarding the number of unique values taken on by each of the structured fields  1947  is also displayed through the user interface. 
       FIG. 20A  illustrates an exemplary user interface screen with a set of event records that may be stored in a raw record data store in accordance with the disclosed embodiments. Each of the five event records comprises two fields, “field A”  2001  and “field B”  2002 , where field A  2101  occurs before a comma delimiter and field B  2102  occurs after the comma delimiter. 
       FIG. 20B  illustrates an exemplary user interface screen for defining constraints for a data model created using the events of  FIG. 20A  in accordance with the disclosed embodiments. The data model “sample_dm” comprises dataset “sample_event,” where “sample_event” is defined as all event records (from the set of 5 in  FIG. 20A ) where “field A” is not equal to 5. Note that there are 4 events in the set shown in  FIG. 20A  where “field A” is not equal to 5. Furthermore, structured field, “field A” is defined as part of the dataset “sample_event.” Note that, “field B” is not defined within the data model and is, therefore, unstructured. Also, it should be noted that the data model “sample_dm” is accelerated as shown in  FIG. 20B . Accordingly, there exists a summarization table (not shown in the user interface) that is used to quickly and efficiently retrieve the events comprising the data model by leveraging posting values. 
       FIG. 20C  illustrates an exemplary user interface showing the manner in which events in the data model of  FIG. 20B  may be retrieved and annotated with structured field in accordance with the disclosed embodiments. Similar to the example in  FIG. 19B , the query  2011  will retrieve all the events in the “sample_dm” data model and display them through the user interface. Accordingly, the 4 events in the data model (as defined by the constraints) are displayed as shown in  FIG. 20C  and annotated with structured field, “field A.” Note, that the value displayed next “field A” is the number of discrete values that “field A” takes on in the events returned (e.g., the value of “4” is displayed because “field A” takes on four discrete values, e.g., 1, 2, 3, and 4). A different user interface may, however, choose to display a different statistic next to the annotated structured fields. 
       FIG. 20D  illustrates an exemplary user interface showing the manner in which a query invoking the accelerated data model of  21 B and comprising a predicate with a structured field may be processed in accordance with the disclosed embodiments. The predicate  2032  in query  2031  can be pushed down because “field A” is structured. As seen in  FIG. 20C  there is only one event that satisfies predicate  2032 , e.g., where “field A” equals a value of “4.” If the data model was not accelerated, it would not be possible to push the predicate down. In this case all the events in the index (all 5 events shown in  FIG. 20A ) may need to be scanned and filtered. However, data model “sample_dm” is accelerated which means a summarization table data structure (comprising indexed field “field A”) may be used to enable predicate pushdown. The summarization table informs the optimizer that only a single event matches the predicate condition and, therefore, the optimizer only needs to scan one event and retrieve a single result as shown in  FIG. 20D . Also, as shown in  FIG. 20D , only “field A” appears in the field picker because the structured fields are extracted. 
       FIG. 21  presents a flowchart illustrating the manner in which structured fields may be emitted in response to a search of an accelerated data model in accordance with the disclosed embodiments. 
     At step  2102 , a pipelined query associated with a data model is received by the query engine. The data model, as explained earlier, can be used to quickly search data to identify a set of events (e.g., a set of events that satisfy the set of search constraints of the data model) and a set of structured fields associated with the set of events (e.g., the set of fields of the data model that are in the set of events identified). 
     At step  2104 , the incoming pipeline query is evaluated. For example, the optimizer receives the initial pipelined query and partitions the pipeline into blocks corresponding to commands in order to extract semantic information regarding the commands in the pipelined query. The optimizer extracts the commands from the pipeline and, for each command in the sequence of commands, semantic information is obtained. Further, the optimizer may then generate an abstract semantic tree (AST) with the semantic information. 
     At step  2106 , a summarization table that accelerates the data model is accessed. As also explained earlier, a data model summarization table for a data model can include or otherwise identify values for the structured fields specified by the data model that are from the events that satisfy the search criteria of the data model. Further, the summarization table may include reference or posting values indicating the location of the events in the data model. 
     At step  2108 , the posting values in the summarization table are used to retrieve the events in the data model. 
     At step  2110 , as shown in  FIG. 20A , if the query does not comprise further pipelined stages, the events in the data model are displayed through a user-interface and annotated with the structured fields defined in the data model. 
     2.11.4. Accelerating Report Generation 
     In some embodiments, a data server system such as the SPLUNK® ENTERPRISE system can accelerate the process of periodically generating updated reports based on query results. To accelerate this process, a summarization engine automatically examines the query to determine whether generation of updated reports can be accelerated by creating intermediate summaries. If reports can be accelerated, the summarization engine periodically generates a summary covering data obtained during a latest non-overlapping time period. For example, where the query seeks events meeting a specified criteria, a summary for the time period includes only events within the time period that meet the specified criteria. Similarly, if the query seeks statistics calculated from the events, such as the number of events that match the specified criteria, then the summary for the time period includes the number of events in the period that match the specified criteria. 
     In addition to the creation of the summaries, the summarization engine schedules the periodic updating of the report associated with the query. During each scheduled report update, the query engine determines whether intermediate summaries have been generated covering portions of the time period covered by the report update. If so, then the report is generated based on the information contained in the summaries. Also, if additional event data has been received and has not yet been summarized, and is required to generate the complete report, the query can be run on this additional event data. Then, the results returned by this query on the additional event data, along with the partial results obtained from the intermediate summaries, can be combined to generate the updated report. This process is repeated each time the report is updated. Alternatively, if the system stores events in buckets covering specific time ranges, then the summaries can be generated on a bucket-by-bucket basis. Note that producing intermediate summaries can save the work involved in re-running the query for previous time periods, so advantageosly only the newer event data needs to be processed while generating an updated report. These report acceleration techniques are described in more detail in U.S. Pat. No. 8,589,403, entitled “COMPRESSED JOURNALING IN EVENT TRACKING FILES FOR METADATA RECOVERY AND REPLICATION”, issued on 19 Nov. 2013, U.S. Pat. No. 8,412,696, entitled “REAL TIME SEARCHING AND REPORTING”, issued on 2 Apr. 2011, and U.S. Pat. Nos. 8,589,375 and 8,589,432, both also entitled “REAL TIME SEARCHING AND REPORTING”, both issued on 19 Nov. 2013, each of which is hereby incorporated by reference in its entirety. 
     2.12. Security Features 
     The SPLUNK® ENTERPRISE platform provides various schemas, dashboards and visualizations that simplify developers&#39; task to create applications with additional capabilities. One such application is the SPLUNK® APP FOR ENTERPRISE SECURITY, which performs monitoring and alerting operations and includes analytics to facilitate identifying both known and unknown security threats based on large volumes of data stored by the SPLUNK® ENTERPRISE system. SPLUNK® APP FOR ENTERPRISE SECURITY provides the security practitioner with visibility into security-relevant threats found in the enterprise infrastructure by capturing, monitoring, and reporting on data from enterprise security devices, systems, and applications. Through the use of SPLUNK® ENTERPRISE searching and reporting capabilities, SPLUNK® APP FOR ENTERPRISE SECURITY provides a top-down and bottom-up view of an organization&#39;s security posture. 
     The SPLUNK® APP FOR ENTERPRISE SECURITY leverages SPLUNK® ENTERPRISE search-time normalization techniques, saved searches, and correlation searches to provide visibility into security-relevant threats and activity and generate notable events for tracking. The App enables the security practitioner to investigate and explore the data to find new or unknown threats that do not follow signature-based patterns. 
     Conventional Security Information and Event Management (SIEM) systems that lack the infrastructure to effectively store and analyze large volumes of security-related data. Traditional SIEM systems typically use fixed schemas to extract data from pre-defined security-related fields at data ingestion time and storing the extracted data in a relational database. This traditional data extraction process (and associated reduction in data size) that occurs at data ingestion time inevitably hampers future incident investigations that may need original data to determine the root cause of a security issue, or to detect the onset of an impending security threat. 
     In contrast, the SPLUNK® APP FOR ENTERPRISE SECURITY system stores large volumes of minimally processed security-related data at ingestion time for later retrieval and analysis at search time when a live security threat is being investigated. To facilitate this data retrieval process, the SPLUNK® APP FOR ENTERPRISE SECURITY provides pre-specified schemas for extracting relevant values from the different types of security-related event data and enables a user to define such schemas. 
     The SPLUNK® APP FOR ENTERPRISE SECURITY can process many types of security-related information. In general, this security-related information can include any information that can be used to identify security threats. For example, the security-related information can include network-related information, such as IP addresses, domain names, asset identifiers, network traffic volume, uniform resource locator strings, and source addresses. The process of detecting security threats for network-related information is further described in U.S. Pat. No. 8,826,434, entitled “SECURITY THREAT DETECTION BASED ON INDICATIONS IN BIG DATA OF ACCESS TO NEWLY REGISTERED DOMAINS”, issued on 2 Sep. 2014, U.S. patent application Ser. No. 13/956,252, entitled “INVESTIGATIVE AND DYNAMIC DETECTION OF POTENTIAL SECURITY-THREAT INDICATORS FROM EVENTS IN BIG DATA”, filed on 31 Jul. 2013, U.S. patent application Ser. No. 14/445,018, entitled “GRAPHIC DISPLAY OF SECURITY THREATS BASED ON INDICATIONS OF ACCESS TO NEWLY REGISTERED DOMAINS”, filed on 28 Jul. 2014, U.S. patent application Ser. No. 14/445,023, entitled “SECURITY THREAT DETECTION OF NEWLY REGISTERED DOMAINS”, filed on 28 Jul. 2014, U.S. patent application Ser. No. 14/815,971, entitled “SECURITY THREAT DETECTION USING DOMAIN NAME ACCESSES”, filed on 1 Aug. 2015, and U.S. patent application Ser. No. 14/815,972, entitled “SECURITY THREAT DETECTION USING DOMAIN NAME REGISTRATIONS”, filed on 1 Aug. 2015, each of which is hereby incorporated by reference in its entirety for all purposes. Security-related information can also include malware infection data and system configuration information, as well as access control information, such as login/logout information and access failure notifications. The security-related information can originate from various sources within a data center, such as hosts, virtual machines, storage devices and sensors. The security-related information can also originate from various sources in a network, such as routers, switches, email servers, proxy servers, gateways, firewalls and intrusion-detection systems. 
     During operation, the SPLUNK® APP FOR ENTERPRISE SECURITY facilitates detecting “notable events” that are likely to indicate a security threat. These notable events can be detected in a number of ways: (1) a user can notice a correlation in the data and can manually identify a corresponding group of one or more events as “notable;” or (2) a user can define a “correlation search” specifying criteria for a notable event, and every time one or more events satisfy the criteria, the application can indicate that the one or more events are notable. A user can alternatively select a pre-defined correlation search provided by the application. Note that correlation searches can be run continuously or at regular intervals (e.g., every hour) to search for notable events. Upon detection, notable events can be stored in a dedicated “notable events index,” which can be subsequently accessed to generate various visualizations containing security-related information. Also, alerts can be generated to notify system operators when important notable events are discovered. 
     The SPLUNK® APP FOR ENTERPRISE SECURITY provides various visualizations to aid in discovering security threats, such as a “key indicators view” that enables a user to view security metrics, such as counts of different types of notable events. For example,  FIG. 9A  illustrates an example key indicators view  900  that comprises a dashboard, which can display a value  901 , for various security-related metrics, such as malware infections  902 . It can also display a change in a metric value  903 , which indicates that the number of malware infections increased by 63 during the preceding interval. Key indicators view  900  additionally displays a histogram panel  904  that displays a histogram of notable events organized by urgency values, and a histogram of notable events organized by time intervals. This key indicators view is described in further detail in pending U.S. patent application Ser. No. 13/956,338, entitled “KEY INDICATORS VIEW”, filed on 31 Jul. 2013, and which is hereby incorporated by reference in its entirety for all purposes. 
     These visualizations can also include an “incident review dashboard” that enables a user to view and act on “notable events.” These notable events can include: (1) a single event of high importance, such as any activity from a known web attacker; or (2) multiple events that collectively warrant review, such as a large number of authentication failures on a host followed by a successful authentication. For example,  FIG. 9B  illustrates an example incident review dashboard  910  that includes a set of incident attribute fields  911  that, for example, enables a user to specify a time range field  912  for the displayed events. It also includes a timeline  913  that graphically illustrates the number of incidents that occurred in time intervals over the selected time range. It additionally displays an events list  914  that enables a user to view a list of all of the notable events that match the criteria in the incident attributes fields  911 . To facilitate identifying patterns among the notable events, each notable event can be associated with an urgency value (e.g., low, medium, high, critical), which is indicated in the incident review dashboard. The urgency value for a detected event can be determined based on the severity of the event and the priority of the system component associated with the event. 
     2.12. Data Center Monitoring 
     As mentioned above, the SPLUNK® ENTERPRISE platform provides various features that simplify the developers&#39;s task to create various applications. One such application is SPLUNK® APP FOR VMWARE® that provides operational visibility into granular performance metrics, logs, tasks and events, and topology from hosts, virtual machines and virtual centers. It empowers administrators with an accurate real-time picture of the health of the environment, proactively identifying performance and capacity bottlenecks. 
     Conventional data-center-monitoring systems lack the infrastructure to effectively store and analyze large volumes of machine-generated data, such as performance information and log data obtained from the data center. In conventional data-center-monitoring systems, machine-generated data is typically pre-processed prior to being stored, for example, by extracting pre-specified data items and storing them in a database to facilitate subsequent retrieval and analysis at search time. However, the rest of the data is not saved and discarded during pre-processing. 
     In contrast, the SPLUNK® APP FOR VMWARE® stores large volumes of minimally processed machine data, such as performance information and log data, at ingestion time for later retrieval and analysis at search time when a live performance issue is being investigated. In addition to data obtained from various log files, this performance-related information can include values for performance metrics obtained through an application programming interface (API) provided as part of the vSphere Hypervisor™ system distributed by VMware, Inc. of Palo Alto, Calif. For example, these performance metrics can include: (1) CPU-related performance metrics; (2) disk-related performance metrics; (3) memory-related performance metrics; (4) network-related performance metrics; (5) energy-usage statistics; (6) data-traffic-related performance metrics; (7) overall system availability performance metrics; (8) cluster-related performance metrics; and (9) virtual machine performance statistics. Such performance metrics are described in U.S. patent application Ser. No. 14/167,316, entitled “CORRELATION FOR USER-SELECTED TIME RANGES OF VALUES FOR PERFORMANCE METRICS OF COMPONENTS IN AN INFORMATION-TECHNOLOGY ENVIRONMENT WITH LOG DATA FROM THAT INFORMATION-TECHNOLOGY ENVIRONMENT”, filed on 29 Jan. 2014, and which is hereby incorporated by reference in its entirety for all purposes. 
     To facilitate retrieving information of interest from performance data and log files, the SPLUNK® APP FOR VMWARE® provides pre-specified schemas for extracting relevant values from different types of performance-related event data, and also enables a user to define such schemas. 
     The SPLUNK® APP FOR VMWARE® additionally provides various visualizations to facilitate detecting and diagnosing the root cause of performance problems. For example, one such visualization is a “proactive monitoring tree” that enables a user to easily view and understand relationships among various factors that affect the performance of a hierarchically structured computing system. This proactive monitoring tree enables a user to easily navigate the hierarchy by selectively expanding nodes representing various entities (e.g., virtual centers or computing clusters) to view performance information for lower-level nodes associated with lower-level entities (e.g., virtual machines or host systems). Example node-expansion operations are illustrated in  FIG. 9C , wherein nodes  933  and  934  are selectively expanded. Note that nodes  931 - 939  can be displayed using different patterns or colors to represent different performance states, such as a critical state, a warning state, a normal state or an unknown/offline state. The ease of navigation provided by selective expansion in combination with the associated performance-state information enables a user to quickly diagnose the root cause of a performance problem. The proactive monitoring tree is described in further detail in U.S. patent application Ser. No. 14/253,490, entitled “PROACTIVE MONITORING TREE WITH SEVERITY STATE SORTING”, filed on 15 Apr. 2014, and U.S. patent application Ser. No. 14/812,948, also entitled “PROACTIVE MONITORING TREE WITH SEVERITY STATE SORTING”, filed on 29 Jul. 2015, each of which is hereby incorporated by reference in its entirety for all purposes. 
     The SPLUNK® APP FOR VMWARE® also provides a user interface that enables a user to select a specific time range and then view heterogeneous data comprising events, log data, and associated performance metrics for the selected time range. For example, the screen illustrated in  FIG. 9D  displays a listing of recent “tasks and events” and a listing of recent “log entries” for a selected time range above a performance-metric graph for “average CPU core utilization” for the selected time range. Note that a user is able to operate pull-down menus  942  to selectively display different performance metric graphs for the selected time range. This enables the user to correlate trends in the performance-metric graph with corresponding event and log data to quickly determine the root cause of a performance problem. This user interface is described in more detail in U.S. patent application Ser. No. 14/167,316, entitled “CORRELATION FOR USER-SELECTED TIME RANGES OF VALUES FOR PERFORMANCE METRICS OF COMPONENTS IN AN INFORMATION-TECHNOLOGY ENVIRONMENT WITH LOG DATA FROM THAT INFORMATION-TECHNOLOGY ENVIRONMENT”, filed on 29 Jan. 2014, and which is hereby incorporated by reference in its entirety for all purposes. 
     2.13. Cloud-Based System Overview 
     The example data intake and query system  108  described in reference to  FIG. 2  comprises several system components, including one or more forwarders, indexers, and search heads. In some environments, a user of a data intake and query system  108  may install and configure, on computing devices owned and operated by the user, one or more software applications that implement some or all of these system components. For example, a user may install a software application on server computers owned by the user and configure each server to operate as one or more of a forwarder, an indexer, a search head, etc. This arrangement generally may be referred to as an “on-premises” solution. That is, the system  108  is installed and operates on computing devices directly controlled by the user of the system. Some users may prefer an on-premises solution because it may provide a greater level of control over the configuration of certain aspects of the system (e.g., security, privacy, standards, controls, etc.). However, other users may instead prefer an arrangement in which the user is not directly responsible for providing and managing the computing devices upon which various components of system  108  operate. 
     In one embodiment, to provide an alternative to an entirely on-premises environment for system  108 , one or more of the components of a data intake and query system instead may be provided as a cloud-based service. In this context, a cloud-based service refers to a service hosted by one more computing resources that are accessible to end users over a network, for example, by using a web browser or other application on a client device to interface with the remote computing resources. For example, a service provider may provide a cloud-based data intake and query system by managing computing resources configured to implement various aspects of the system (e.g., forwarders, indexers, search heads, etc.) and by providing access to the system to end users via a network. Typically, a user may pay a subscription or other fee to use such a service. Each subscribing user of the cloud-based service may be provided with an account that enables the user to configure a customized cloud-based system based on the user&#39;s preferences. 
       FIG. 10  illustrates a block diagram of an example cloud-based data intake and query system. Similar to the system of  FIG. 2 , the networked computer system  1000  includes input data sources  202  and forwarders  204 . These input data sources and forwarders may be in a subscriber&#39;s private computing environment. Alternatively, they might be directly managed by the service provider as part of the cloud service. In the example system  1000 , one or more forwarders  204  and client devices  1002  are coupled to a cloud-based data intake and query system  1006  via one or more networks  1004 . Network  1004  broadly represents one or more LANs, WANs, cellular networks, intranetworks, internetworks, etc., using any of wired, wireless, terrestrial microwave, satellite links, etc., and may include the public Internet, and is used by client devices  1002  and forwarders  204  to access the system  1006 . Similar to the system of  108 , each of the forwarders  204  may be configured to receive data from an input source and to forward the data to other components of the system  1006  for further processing. 
     In an embodiment, a cloud-based data intake and query system  1006  may comprise a plurality of system instances  1008 . In general, each system instance  1008  may include one or more computing resources managed by a provider of the cloud-based system  1006  made available to a particular subscriber. The computing resources comprising a system instance  1008  may, for example, include one or more servers or other devices configured to implement one or more forwarders, indexers, search heads, and other components of a data intake and query system, similar to system  108 . As indicated above, a subscriber may use a web browser or other application of a client device  1002  to access a web portal or other interface that enables the subscriber to configure an instance  1008 . 
     Providing a data intake and query system as described in reference to system  108  as a cloud-based service presents a number of challenges. Each of the components of a system  108  (e.g., forwarders, indexers and search heads) may at times refer to various configuration files stored locally at each component. These configuration files typically may involve some level of user configuration to accommodate particular types of data a user desires to analyze and to account for other user preferences. However, in a cloud-based service context, users typically may not have direct access to the underlying computing resources implementing the various system components (e.g., the computing resources comprising each system instance  1008 ) and may desire to make such configurations indirectly, for example, using one or more web-based interfaces. Thus, the techniques and systems described herein for providing user interfaces that enable a user to configure source type definitions are applicable to both on-premises and cloud-based service contexts, or some combination thereof (e.g., a hybrid system where both an on-premises environment such as SPLUNK® ENTERPRISE and a cloud-based environment such as SPLUNK CLOUD™ are centrally visible). 
     2.14. Searching Externally Archived Data 
       FIG. 11  shows a block diagram of an example of a data intake and query system  108  that provides transparent search facilities for data systems that are external to the data intake and query system. Such facilities are available in the HUNK® system provided by Splunk Inc. of San Francisco, Calif. HUNK® represents an analytics platform that enables business and IT teams to rapidly explore, analyze, and visualize data in Hadoop and NoSQL data stores. 
     The search head  210  of the data intake and query system receives search requests from one or more client devices  1104  over network connections  1120 . As discussed above, the data intake and query system  108  may reside in an enterprise location, in the cloud, etc.  FIG. 11  illustrates that multiple client devices  1104   a ,  1104   b , . . . ,  1104   n  may communicate with the data intake and query system  108 . The client devices  1104  may communicate with the data intake and query system using a variety of connections. For example, one client device in  FIG. 11  is illustrated as communicating over an Internet (Web) protocol, another client device is illustrated as communicating via a command line interface, and another client device is illustrated as communicating via a system developer kit (SDK). 
     The search head  210  analyzes the received search request to identify request parameters. If a search request received from one of the client devices  1104  references an index maintained by the data intake and query system, then the search head  210  connects to one or more indexers  206  of the data intake and query system for the index referenced in the request parameters. That is, if the request parameters of the search request reference an index, then the search head accesses the data in the index via the indexer. The data intake and query system  108  may include one or more indexers  206 , depending on system access resources and requirements. As described further below, the indexers  206  retrieve data from their respective local data stores  208  as specified in the search request. The indexers and their respective data stores can comprise one or more storage devices and typically reside on the same system, though they may be connected via a local network connection. 
     If the request parameters of the received search request reference an external data collection, which is not accessible to the indexers  206  or under the management of the data intake and query system, then the search head  210  can access the external data collection through an External Result Provider (ERP) process  1110 . An external data collection may be referred to as a “virtual index” (plural, “virtual indices”). An ERP process provides an interface through which the search head  210  may access virtual indices. 
     Thus, a search reference to an index of the system relates to a locally stored and managed data collection. In contrast, a search reference to a virtual index relates to an externally stored and managed data collection, which the search head may access through one or more ERP processes  1110 ,  1112 .  FIG. 11  shows two ERP processes  1110 ,  1112  that connect to respective remote (external) virtual indices, which are indicated as a Hadoop or another system  1114  (e.g., Amazon S3, Amazon EMR, other Hadoop Compatible File Systems (HCFS), etc.) and a relational database management system (RDBMS)  1116 . Other virtual indices may include other file organizations and protocols, such as Structured Query Language (SQL) and the like. The ellipses between the ERP processes  1110 ,  1112  indicate optional additional ERP processes of the data intake and query system  108 . An ERP process may be a computer process that is initiated or spawned by the search head  210  and is executed by the search data intake and query system  108 . Alternatively or additionally, an ERP process may be a process spawned by the search head  210  on the same or different host system as the search head  210  resides. 
     The search head  210  may spawn a single ERP process in response to multiple virtual indices referenced in a search request, or the search head may spawn different ERP processes for different virtual indices. Generally, virtual indices that share common data configurations or protocols may share ERP processes. For example, all search query references to a Hadoop file system may be processed by the same ERP process, if the ERP process is suitably configured. Likewise, all search query references to an SQL database may be processed by the same ERP process. In addition, the search head may provide a common ERP process for common external data source types (e.g., a common vendor may utilize a common ERP process, even if the vendor includes different data storage system types, such as Hadoop and SQL). Common indexing schemes also may be handled by common ERP processes, such as flat text files or Weblog files. 
     The search head  210  determines the number of ERP processes to be initiated via the use of configuration parameters that are included in a search request message. Generally, there is a one-to-many relationship between an external results provider “family” and ERP processes. There is also a one-to-many relationship between an ERP process and corresponding virtual indices that are referred to in a search request. For example, using RDBMS, assume two independent instances of such a system by one vendor, such as one RDBMS for production and another RDBMS used for development. In such a situation, it is likely preferable (but optional) to use two ERP processes to maintain the independent operation as between production and development data. Both of the ERPs, however, will belong to the same family, because the two RDBMS system types are from the same vendor. 
     The ERP processes  1110 ,  1112  receive a search request from the search head  210 . The search head may optimize the received search request for execution at the respective external virtual index. Alternatively, the ERP process may receive a search request as a result of analysis performed by the search head or by a different system process. The ERP processes  1110 ,  1112  can communicate with the search head  210  via conventional input/output routines (e.g., standard in/standard out, etc.). In this way, the ERP process receives the search request from a client device such that the search request may be efficiently executed at the corresponding external virtual index. 
     The ERP processes  1110 ,  1112  may be implemented as a process of the data intake and query system. Each ERP process may be provided by the data intake and query system, or may be provided by process or application providers who are independent of the data intake and query system. Each respective ERP process may include an interface application installed at a computer of the external result provider that ensures proper communication between the search support system and the external result provider. The ERP processes  1110 ,  1112  generate appropriate search requests in the protocol and syntax of the respective virtual indices  1114 ,  1116 , each of which corresponds to the search request received by the search head  210 . Upon receiving search results from their corresponding virtual indices, the respective ERP process passes the result to the search head  210 , which may return or display the results or a processed set of results based on the returned results to the respective client device. 
     Client devices  1104  may communicate with the data intake and query system  108  through a network interface  1120 , e.g., one or more LANs, WANs, cellular networks, intranetworks, or internetworks using any of wired, wireless, terrestrial microwave, satellite links, etc., and may include the public Internet. 
     The analytics platform utilizing the External Result Provider process described in more detail in U.S. Pat. No. 8,738,629, entitled “EXTERNAL RESULT PROVIDED PROCESS FOR RETRIEVING DATA STORED USING A DIFFERENT CONFIGURATION OR PROTOCOL”, issued on 27 May 2014, U.S. Pat. No. 8,738,587, entitled “PROCESSING A SYSTEM SEARCH REQUEST BY RETRIEVING RESULTS FROM BOTH A NATIVE INDEX AND A VIRTUAL INDEX”, issued on 25 Jul. 2013, U.S. patent application Ser. No. 14/266,832, entitled “PROCESSING A SYSTEM SEARCH REQUEST ACROSS DISPARATE DATA COLLECTION SYSTEMS”, filed on 1 May 2014, and U.S. patent application Ser. No. 14/449,144, entitled “PROCESSING A SYSTEM SEARCH REQUEST INCLUDING EXTERNAL DATA SOURCES”, filed on 31 Jul. 2014, each of which is hereby incorporated by reference in its entirety for all purposes. 
     2.14.1. ERP Process Features 
     The ERP processes described above may include two operation modes: a streaming mode and a reporting mode. The ERP processes can operate in streaming mode only, in reporting mode only, or in both modes simultaneously. Operating in both modes simultaneously is referred to as mixed mode operation. In a mixed mode operation, the ERP at some point can stop providing the search head with streaming results and only provide reporting results thereafter, or the search head at some point may start ignoring streaming results it has been using and only use reporting results thereafter. 
     The streaming mode returns search results in real time, with minimal processing, in response to the search request. The reporting mode provides results of a search request with processing of the search results prior to providing them to the requesting search head, which in turn provides results to the requesting client device. ERP operation with such multiple modes provides greater performance flexibility with regard to report time, search latency, and resource utilization. 
     In a mixed mode operation, both streaming mode and reporting mode are operating simultaneously. The streaming mode results (e.g., the raw data obtained from the external data source) are provided to the search head, which can then process the results data (e.g., break the raw data into events, timestamp it, filter it, etc.) and integrate the results data with the results data from other external data sources, or from data stores of the search head. The search head performs such processing and can immediately start returning interim (streaming mode) results to the user at the requesting client device; simultaneously, the search head is waiting for the ERP process to process the data it is retrieving from the external data source as a result of the concurrently executing reporting mode. 
     In some instances, the ERP process initially operates in a mixed mode, such that the streaming mode operates to enable the ERP quickly to return interim results (e.g., some of the raw or unprocessed data necessary to respond to a search request) to the search head, enabling the search head to process the interim results and begin providing to the client or search requester interim results that are responsive to the query. Meanwhile, in this mixed mode, the ERP also operates concurrently in reporting mode, processing portions of raw data in a manner responsive to the search query. Upon determining that it has results from the reporting mode available to return to the search head, the ERP may halt processing in the mixed mode at that time (or some later time) by stopping the return of data in streaming mode to the search head and switching to reporting mode only. The ERP at this point starts sending interim results in reporting mode to the search head, which in turn may then present this processed data responsive to the search request to the client or search requester. Typically the search head switches from using results from the ERP&#39;s streaming mode of operation to results from the ERP&#39;s reporting mode of operation when the higher bandwidth results from the reporting mode outstrip the amount of data processed by the search head in the streaming mode of ERP operation. 
     A reporting mode may have a higher bandwidth because the ERP does not have to spend time transferring data to the search head for processing all the raw data. In addition, the ERP may optionally direct another processor to do the processing. 
     The streaming mode of operation does not need to be stopped to gain the higher bandwidth benefits of a reporting mode; the search head could simply stop using the streaming mode results—and start using the reporting mode results—when the bandwidth of the reporting mode has caught up with or exceeded the amount of bandwidth provided by the streaming mode. Thus, a variety of triggers and ways to accomplish a search head&#39;s switch from using streaming mode results to using reporting mode results may be appreciated by one skilled in the art. 
     The reporting mode can involve the ERP process (or an external system) performing event breaking, time stamping, filtering of events to match the search query request, and calculating statistics on the results. The user can request particular types of data, such as if the search query itself involves types of events, or the search request may ask for statistics on data, such as on events that meet the search request. In either case, the search head understands the query language used in the received query request, which may be a proprietary language. One examplary query language is Splunk Processing Language (SPL) developed by the assignee of the application, Splunk Inc. The search head typically understands how to use that language to obtain data from the indexers, which store data in a format used by the SPLUNK® Enterprise system. 
     The ERP processes support the search head, as the search head is not ordinarily configured to understand the format in which data is stored in external data sources such as Hadoop or SQL data systems. Rather, the ERP process performs that translation from the query submitted in the search support system&#39;s native format (e.g., SPL if SPLUNK® ENTERPRISE is used as the search support system) to a search query request format that will be accepted by the corresponding external data system. The external data system typically stores data in a different format from that of the search support system&#39;s native index format, and it utilizes a different query language (e.g., SQL or MapReduce, rather than SPL or the like). 
     As noted, the ERP process can operate in the streaming mode alone. After the ERP process has performed the translation of the query request and received raw results from the streaming mode, the search head can integrate the returned data with any data obtained from local data sources (e.g., native to the search support system), other external data sources, and other ERP processes (if such operations were required to satisfy the terms of the search query). An advantage of mixed mode operation is that, in addition to streaming mode, the ERP process is also executing concurrently in reporting mode. Thus, the ERP process (rather than the search head) is processing query results (e.g., performing event breaking, timestamping, filtering, possibly calculating statistics if required to be responsive to the search query request, etc.). It should be apparent to those skilled in the art that additional time is needed for the ERP process to perform the processing in such a configuration. Therefore, the streaming mode will allow the search head to start returning interim results to the user at the client device before the ERP process can complete sufficient processing to start returning any search results. The switchover between streaming and reporting mode happens when the ERP process determines that the switchover is appropriate, such as when the ERP process determines it can begin returning meaningful results from its reporting mode. 
     The operation described above illustrates the source of operational latency: streaming mode has low latency (immediate results) and usually has relatively low bandwidth (fewer results can be returned per unit of time). In contrast, the concurrently running reporting mode has relatively high latency (it has to perform a lot more processing before returning any results) and usually has relatively high bandwidth (more results can be processed per unit of time). For example, when the ERP process does begin returning report results, it returns more processed results than in the streaming mode, because, e.g., statistics only need to be calculated to be responsive to the search request. That is, the ERP process doesn&#39;t have to take time to first return raw data to the search head. As noted, the ERP process could be configured to operate in streaming mode alone and return just the raw data for the search head to process in a way that is responsive to the search request. Alternatively, the ERP process can be configured to operate in the reporting mode only. Also, the ERP process can be configured to operate in streaming mode and reporting mode concurrently, as described, with the ERP process stopping the transmission of streaming results to the search head when the concurrently running reporting mode has caught up and started providing results. The reporting mode does not require the processing of all raw data that is responsive to the search query request before the ERP process starts returning results; rather, the reporting mode usually performs processing of chunks of events and returns the processing results to the search head for each chunk. 
     For example, an ERP process can be configured to merely return the contents of a search result file verbatim, with little or no processing of results. That way, the search head performs all processing (such as parsing byte streams into events, filtering, etc.). The ERP process can be configured to perform additional intelligence, such as analyzing the search request and handling all the computation that a native search indexer process would otherwise perform. In this way, the configured ERP process provides greater flexibility in features while operating according to desired preferences, such as response latency and resource requirements. 
     2.14. IT Service Monitoring 
     As previously mentioned, the SPLUNK® ENTERPRISE platform provides various schemas, dashboards and visualizations that make it easy for developers to create applications to provide additional capabilities. One such application is SPLUNK® IT SERVICE INTELLIGENCE™, which performs monitoring and alerting operations. It also includes analytics to help an analyst diagnose the root cause of performance problems based on large volumes of data stored by the SPLUNK® ENTERPRISE system as correlated to the various services an IT organization provides (a service-centric view). This differs significantly from conventional IT monitoring systems that lack the infrastructure to effectively store and analyze large volumes of service-related event data. Traditional service monitoring systems typically use fixed schemas to extract data from pre-defined fields at data ingestion time, wherein the extracted data is typically stored in a relational database. This data extraction process and associated reduction in data content that occurs at data ingestion time inevitably hampers future investigations, when all of the original data may be needed to determine the root cause of or contributing factors to a service issue. 
     In contrast, a SPLUNK® IT SERVICE INTELLIGENCE™ system stores large volumes of minimally-processed service-related data at ingestion time for later retrieval and analysis at search time, to perform regular monitoring, or to investigate a service issue. To facilitate this data retrieval process, SPLUNK® IT SERVICE INTELLIGENCE™ enables a user to define an IT operations infrastructure from the perspective of the services it provides. In this service-centric approach, a service such as corporate e-mail may be defined in terms of the entities employed to provide the service, such as host machines and network devices. Each entity is defined to include information for identifying all of the event data that pertains to the entity, whether produced by the entity itself or by another machine, and considering the many various ways the entity may be identified in raw machine data (such as by a URL, an IP address, or machine name). The service and entity definitions can organize event data around a service so that all of the event data pertaining to that service can be easily identified. This capability provides a foundation for the implementation of Key Performance Indicators. 
     One or more Key Performance Indicators (KPI&#39;s) are defined for a service within the SPLUNK® IT SERVICE INTELLIGENCE™ application. Each KPI measures an aspect of service performance at a point in time or over a period of time (aspect KPI&#39;s). Each KPI is defined by a search query that derives a KPI value from the machine data of events associated with the entities that provide the service. Information in the entity definitions may be used to identify the appropriate events at the time a KPI is defined or whenever a KPI value is being determined. The KPI values derived over time may be stored to build a valuable repository of current and historical performance information for the service, and the repository, itself, may be subject to search query processing. Aggregate KPIs may be defined to provide a measure of service performance calculated from a set of service aspect KPI values; this aggregate may even be taken across defined timeframes or across multiple services. A particular service may have an aggregate KPI derived from substantially all of the aspect KPI&#39;s of the service to indicate an overall health score for the service. 
     SPLUNK® IT SERVICE INTELLIGENCE™ facilitates the production of meaningful aggregate KPI&#39;s through a system of KPI thresholds and state values. Different KPI definitions may produce values in different ranges, and so the same value may mean something very different from one KPI definition to another. To address this, SPLUNK® IT SERVICE INTELLIGENCE™ implements a translation of individual KPI values to a common domain of “state” values. For example, a KPI range of values may be 1-100, or 50-275, while values in the state domain may be ‘critical,’ ‘warning,’ “normal,” and ‘informational’. Thresholds associated with a particular KPI definition determine ranges of values for that KPI that correspond to the various state values. In one case, KPI values 95-100 may be set to correspond to ‘critical’ in the state domain. KPI values from disparate KPI&#39;s can be processed uniformly once they are translated into the common state values using the thresholds. For example, “normal 80% of the time” can be applied across various KPI&#39;s. To provide meaningful aggregate KPI&#39;s, a weighting value can be assigned to each KPI so that its influence on the calculated aggregate KPI value is increased or decreased relative to the other KPI&#39;s. 
     One service in an IT environment often impacts, or is impacted by, another service. SPLUNK® IT SERVICE INTELLIGENCE™ can reflect these dependencies. For example, a dependency relationship between a corporate e-mail service and a centralized authentication service can be reflected by recording an association between their respective service definitions. The recorded associations establish a service dependency topology that informs the data or selection options presented in a GUI, for example. (The service dependency topology is like a “map” showing how services are connected based on their dependencies.) The service topology may itself be depicted in a GUI and may be interactive to allow navigation among related services. 
     Entity definitions in SPLUNK® IT SERVICE INTELLIGENCE™ can include informational fields that can serve as metadata, implied data fields, or attributed data fields for the events identified by other aspects of the entity definition. Entity definitions in SPLUNK® IT SERVICE INTELLIGENCE™ can also be created and updated by an import of tabular data (as represented in a CSV, another delimited file, or a search query result set). The import may be GUI-mediated or processed using import parameters from a GUI-based import definition process. Entity definitions in SPLUNK® IT SERVICE INTELLIGENCE™ can also be associated with a service by means of a service definition rule. Processing the rule results in the matching entity definitions being associated with the service definition. The rule can be processed at creation time, and thereafter on a scheduled or on-demand basis. This allows dynamic, rule-based updates to the service definition. 
     During operation, SPLUNK® IT SERVICE INTELLIGENCE™ can recognize so-called “notable events” that may indicate a service performance problem or other situation of interest. These notable events can be recognized by a “correlation search” specifying trigger criteria for a notable event: every time KPI values satisfy the criteria, the application indicates a notable event. A severity level for the notable event may also be specified. Furthermore, when trigger criteria are satisfied, the correlation search may additionally or alternatively cause a service ticket to be created in an IT service management (ITSM) system, such as a systems available from ServiceNow, Inc., of Santa Clara, Calif. 
     SPLUNK® IT SERVICE INTELLIGENCE™ provides various visualizations built on its service-centric organization of event data and the KPI values generated and collected. Visualizations can be particularly useful for monitoring or investigating service performance. SPLUNK® IT SERVICE INTELLIGENCE™ provides a service monitoring interface suitable as the home page for ongoing IT service monitoring. The interface is appropriate for settings such as desktop use or for a wall-mounted display in a network operations center (NOC). The interface may prominently display a services health section with tiles for the aggregate KPI&#39;s indicating overall health for defined services and a general KPI section with tiles for KPI&#39;s related to individual service aspects. These tiles may display KPI information in a variety of ways, such as by being colored and ordered according to factors like the KPI state value. They also can be interactive and navigate to visualizations of more detailed KPI information. 
     SPLUNK® IT SERVICE INTELLIGENCE™ provides a service-monitoring dashboard visualization based on a user-defined template. The template can include user-selectable widgets of varying types and styles to display KPI information. The content and the appearance of widgets can respond dynamically to changing KPI information. The KPI widgets can appear in conjunction with a background image, user drawing objects, or other visual elements, that depict the IT operations environment, for example. The KPI widgets or other GUI elements can be interactive so as to provide navigation to visualizations of more detailed KPI information. 
     SPLUNK® IT SERVICE INTELLIGENCE™ provides a visualization showing detailed time-series information for multiple KPI&#39;s in parallel graph lanes. The length of each lane can correspond to a uniform time range, while the width of each lane may be automatically adjusted to fit the displayed KPI data. Data within each lane may be displayed in a user selectable style, such as a line, area, or bar chart. During operation a user may select a position in the time range of the graph lanes to activate lane inspection at that point in time. Lane inspection may display an indicator for the selected time across the graph lanes and display the KPI value associated with that point in time for each of the graph lanes. The visualization may also provide navigation to an interface for defining a correlation search, using information from the visualization to pre-populate the definition. 
     SPLUNK® IT SERVICE INTELLIGENCE™ provides a visualization for incident review showing detailed information for notable events. The incident review visualization may also show summary information for the notable events over a time frame, such as an indication of the number of notable events at each of a number of severity levels. The severity level display may be presented as a rainbow chart with the warmest color associated with the highest severity classification. The incident review visualization may also show summary information for the notable events over a time frame, such as the number of notable events occurring within segments of the time frame. The incident review visualization may display a list of notable events within the time frame ordered by any number of factors, such as time or severity. The selection of a particular notable event from the list may display detailed information about that notable event, including an identification of the correlation search that generated the notable event. 
     SPLUNK® IT SERVICE INTELLIGENCE™ provides pre-specified schemas for extracting relevant values from the different types of service-related event data. It also enables a user to define such schemas.