Patent Description:
A query is a request for information from an information retrieval system. There are three general methods for posing queries: menu driven, querying by example and query language formulation. In the first instance, a query is formulated and issued based upon the selection of parameters in a menu. In the second instance, the information retrieval system presents a blank record and allows the end user to specify the fields and values that define the query. In the third instance, the end user formulates the query utilizing a stylized query written in a query language. The latter is the most complex method because it requires the use of a specialized language, but the latter is also the most powerful as it is the least constrained mode of querying an information retrieval system.

Queries generally are issued either on demand through a query interface, or programmatically at the time of executing a computer program. But, queries also may be issued in batch mode. That is to say, a query may be specified at one time, but execution of the query against the information retrieval system may be deferred to a later time. In this regard, in an information retrieval system, it is common for multiple users to concurrently submit queries to the database for execution. Consequently, if the information retrieval system lacks sufficient computing resources to execute all of the submitted queries simultaneously, the information retrieval system must defer execution of one or more of those queries while only a subset of the queries may be processed immediately. The process of determining which queries to defer and at what time the deferred queries are to execute is known as query scheduling.

One way to perform query scheduling is to execute incoming queries in the order they arrive referred to as a "first-come-first-serve" approach. However, the first-come-first serve approach cannot differentiate between queries that have differing response time requirements, some queries being more time sensitive than others. If queries are simply scheduled according to order of arrival, some time-sensitive queries may be forced to wait behind time-insensitive queries, which can adversely affect the usability and responsiveness of the information retrieval system.

Query scheduling also may be performed according to fixed priority. In fixed priority scheduling, each query is assigned a priority based on one or more properties known at the time of query arrival such as the identity or type of the query requestor. Thereafter, each query may be scheduled according to an assigned priority. As can be seen, fixed priority scheduling avoids the problems of the first-come-first-serve approach since time-sensitive queries can be prioritized over less time-sensitive queries. Yet, fixed priority scheduling cannot account for "heavy" queries that take a relatively long time to execute and "light" queries that take a relatively short time to execute, such as on the order of milliseconds or seconds.

<CIT> discloses a query handler that may be configured to receive a query which is applicable against different combinations of a plurality of remote databases and a corresponding plurality of replica databases including at least some replicated data of respective ones of the remote databases, wherein the query arrives at a plurality of query arrival times and is executed at a plurality of query execution times. A replication manager may be configured to execute a synchronization plan for at least one selected replica database in which a selected synchronization timestamp of the at least one selected replica database is updated to a target synchronization timestamp, wherein the synchronization occurs during a synchronization processing time. A synchronization scheduler may be configured to schedule the synchronization plan to increase an information value of a query response, including selecting the target synchronization timestamp including relating the synchronization processing time to a selected query execution time.

<CIT> refers to resource assignment for jobs in a system having a processing pipeline.

In <CIT>, a set of jobs to be scheduled is identified in the system including the processing pipeline having plural processing stages that apply corresponding different processing to a data update to allow the data update to be stored. The set of jobs is based on one or both of the data update and a query that is to access data in the system. The set of jobs is scheduled by assigning resources to perform the set of jobs, where assigning the resources is subject to at least one constraint selected from at least one constraint associated with the data update and at least one constraint associated with the query.

Objects of the present invention are achieved by subject matters of independent claims. Dependent claims define some of possible embodiments of the present invention as defined in the independent claims.

Embodiments of the present disclosure address deficiencies of the art in respect to query scheduling and provide a novel and non-obvious method, system and computer program product for optimal query scheduling according to data freshness requirements. In an embodiment of the disclosure, a process for optimal query scheduling includes receiving in an information retrieval data processing system, a request to accelerate query execution of a specified query to a time prior to a scheduled time. A specific field is then identified in the specified query that corresponds to data in a database. Thereafter, a freshness of data requirement for the specific field is retrieved along with a frequency of change the data corresponding to the specific field. It is then determined if execution of the specific query at the time prior to the scheduled time will violate the freshness of data requirement based upon the frequency of change of the data corresponding of the specific field. The specific query is then scheduled for execution at the time prior to the scheduled time only if the execution of the specific query is determined not to violate the freshness of data requirement. But otherwise, the scheduled time is maintained for executing the specific query.

In one aspect of the embodiment, the time prior is a time that is under-scheduled with fewer scheduled queries consuming fewer resources of the information retrieval data processing system than available resources of the information retrieval data processing system at the located time or scheduled time and that has enough of the available resources to support execution of the specific query. In another aspect of the embodiment, the method further includes maintaining the scheduled time for executing the specific query even though the specific query is determined not to violate the freshness of data requirement on condition that it is determined that the specific query has an estimated cost of execution that is below a threshold value. In yet another aspect of the embodiment, the estimated cost of execution is computed by matching at least a portion of each of the specific query to an entry in a table of queries fragments and corresponding historical execution times.

In another embodiment of the disclosure, an information retrieval data processing system is adapted for optimal query scheduling according to data freshness requirements. The system includes a host computing platform having one or more computers each with memory and at least one processor. The system further includes a query interface coupled to a database. The query interface receives from requesters from over a computer communications network, requests to schedule queries against the database, and in response, schedules the queries for execution so as to return different results sets to the requesters. Finally, the system includes an optimal query scheduling module.

The module includes computer program instructions that when executing in the memory of the host computing platform, are operable to receive a request to accelerate query execution of a specified query to a time prior to a scheduled time and to identify in the specified query, a specific field corresponding to data in a database. The program instructions further are enabled to retrieve a freshness of data requirement for the specific field and a frequency of change the data corresponding to the specific field, and to determine if execution of the specific query at the time prior to the scheduled time instead of the scheduled time violates the freshness of data requirement based upon the frequency of change of the data corresponding of the specific field. Finally, the program instructions are enabled to schedule the specific query for execution at the time prior to the scheduled time on condition that the execution of the specific query is determined not to violate the freshness of data requirement by scheduling the specific query at the time prior to the scheduled time. But otherwise, the program instructions are enabled to maintain the scheduled time for executing the specific query.

Additional aspects of the disclosure will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the disclosure. The aspects of the disclosure will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims.

The accompanying drawings, which are incorporated in and constitute part of this specification, illustrate embodiments of the disclosure and together with the description, serve to explain the principles of the disclosure. The embodiments illustrated herein are presently preferred, it being understood, however, that the disclosure is not limited to the precise arrangements and instrumentalities shown, wherein:.

Embodiments of the disclosure provide for the optimal query scheduling of one or more queries in an information retrieval data processing system according to data freshness requirements. In accordance with an embodiment of the disclosure, a request may be received in the information retrieval data processing system for the acceleration of query execution of a specified query from the scheduled time, to a time prior to a scheduled time. In response to the receipt of the request, a specific field that corresponds to data in a database may be identified within the specified query. As well, a freshness of data requirement is retrieved for the specific field as is a frequency of change the data corresponding to the specific field. Thereafter, it may be determined if execution of the specific query at the time prior to the scheduled time instead of the scheduled time violates the freshness of data requirement based upon the frequency of change of the data corresponding of the specific field. On the condition that the execution of the specific query is determined not to violate the freshness of data requirement by scheduling the specific query at the time prior to the scheduled time, the specific query may be scheduled for execution at the time prior to the scheduled time. But, otherwise the scheduled time for executing the specific query may be maintained.

In further illustration of an exemplary embodiment of the disclosure, <FIG> pictorially shows a process for optimal query scheduling for an information retrieval data processing system according to data freshness requirements. As shown in <FIG>, a request <NUM> is received requesting the acceleration of the scheduling of a query <NUM> to a specified time <NUM> earlier than an existing scheduled time for the query. A field <NUM> of a database or data model implicated by the query <NUM> is identified. Thereafter, a data freshness requirement <NUM> for the field <NUM> is retrieved--specifically, a previously stored indication of how recently updated data for the field <NUM> must be at the time of executing a query accessing data in the field <NUM>, whether directly are as part of an aggregation. As well, an observed volatility <NUM> of the field <NUM> is retrieved--specifically, an indication of how frequently the data in the field <NUM> has been updated in the past.

Thereafter, the freshness requirement <NUM> is compared to the observed volatility <NUM> at the specified time <NUM> relative to a time at which the request <NUM> had been received in order to determine the expected freshness of data in the field <NUM> at the specified time <NUM>. To the extent that the acceleration of scheduling of the query <NUM> to the specified time <NUM> will lead to a violation of the freshness requirement <NUM>, the request <NUM> is rejected and the query <NUM> remains in the schedule <NUM> for execution at the previously scheduled time <NUM>. But otherwise, the query <NUM> is rescheduled in the schedule <NUM> to the specified time <NUM>. Optionally, an execution cost <NUM> of the query <NUM> is determined based upon at least a portion of the query <NUM>. To the extent that the execution cost is below a threshold value, no re-scheduling to the specified time <NUM> is permitted.

The process described in connection with <FIG> can be implemented within an information retrieval data processing system <NUM>. In further illustration, <FIG> schematically shows an information retrieval data processing system configured for optimal query scheduling. The system includes a host computing platform <NUM> that includes one or more computers, each with memory and at least one processor. The system also includes a query interface <NUM> to a database <NUM> (or a data model modeling data in the database <NUM>). The query interface <NUM> is configured to receive queries from over computer communications network <NUM> from requesters <NUM> (e.g., query clients) executing in respectively different computing devices <NUM>, and to schedule the execution of each of the received queries in a query schedule <NUM>, with each of the queries being assigned a specific time (day/date/time or any combination thereof) for execution. The query interface <NUM> further is configured to provide to requesting ones of the query clients <NUM>, corresponding results for submitted and executed queries.

Of importance, the system includes an optimal query scheduler module <NUM>. The module <NUM> includes computer program instructions which when executed in the host computing platform <NUM>, are enabled to receive from the query clients <NUM>, individual requests to accelerate the execution of a specified query to a time prior to a previously scheduled time. The computer program instructions additionally are enabled upon execution to consult an execution cost table <NUM> correlating different query portions to known execution costs in order to identify an entry in the table <NUM> matching a portion of the specified query so as to predict an execution cost of the specified query.

The computer program instructions are further enabled during execution, to the extent that the predicted execution cost exceeds a threshold value, so as to warrant acceleration of scheduling, to identify a field implicated by the specified query and determine in a data freshness table <NUM> a known volatility of data for the identified field and a required freshness of data for the identified field at a time of executing a query implicating the field. Finally, the computer program instructions are enabled during execution to accelerate the scheduling of the execution of the query to the time to the previously scheduled time in the query schedule <NUM> so long as the determined volatility for the specified query does not produce data with a freshness value that falls below the freshness requirement, e.g. the data will have likely changed subsequent to the requested time and prior to the previously scheduled time. But otherwise, the computer program instructions are enabled to reject the request for accelerated scheduling in the query schedule <NUM>.

In even yet further illustration of the operation of the optimal query scheduler module <NUM>, <FIG> is a flow chart illustrating a method for optimal query scheduling for an information retrieval data processing system. Beginning in block <NUM>, a request to accelerate the scheduling of a query to a time prior to a previously scheduled time is received. In block <NUM>, a query implicated by the request is identified along with the specified time for rescheduling. In block <NUM>, a field implicated by the query is selected and in block <NUM>, a freshness requirement for the field is retrieved.

Then, in block <NUM>, an observed volatility of the field is also retrieved and in block <NUM>, the freshness of data in the field is predicted for the specified time based upon the observed volatility. In this regard, a data freshness table may continuously or periodically update a measure of how frequently data for different fields in the database or data model are updated. In decision block <NUM>, the predicted freshness is compared to the freshness requirement in order to determine if rescheduling the query to the specified time will violate the freshness requirement. That is, if it is determined that the data for the field is predicted to update in the period between the specified time and the previously scheduled time rendering the data premature and un-fresh at the specified time, a violation will have occurred. If not, the query is rescheduled to the specified time prior to the previously scheduled time. But otherwise, in block <NUM>, the request is rejected.

The present disclosure may be embodied within a system, a method, a computer program product or any combination thereof. The computer program product may include a computer readable storage medium or media having computer readable program instructions thereon for causing a processor to carry out aspects of the present disclosure.

Computer readable program instructions described herein can be downloaded to respective computing/processing devices from a computer readable storage medium or to an external computer or external storage device via a network.

These computer readable program instructions may be provided to a processor of a general-purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks. These computer readable program instructions may also be stored in a computer readable storage medium that can direct a computer, a programmable data processing apparatus, and/or other devices to function in a particular manner, such that the computer readable storage medium having instructions stored therein includes an article of manufacture including instructions which implement aspects of the function/act specified in the flowchart and/or block diagram block or blocks.

In this regard, each block in the flowchart or block diagrams may represent a module, segment, or portion of instructions, which includes one or more executable instructions for implementing the specified logical function(s).

Finally, the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. It will be further understood that the terms "includes" and/or "including," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

The corresponding structures, materials, acts of all means or step plus function elements in the claims below are intended to include any structure, material, or act for performing the function in combination with other claimed elements as specifically claimed. The description of the present disclosure has been presented for purposes of illustration and description, but is not intended to be exhaustive or limited to the disclosure in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope of the disclosure The embodiment was chosen and described in order to best explain the principles of the disclosure and the practical application, and to enable others of ordinary skill in the art to understand the disclosure for various embodiments with various modifications as are suited to the particular use contemplated.

Claim 1:
A method for optimal query scheduling, the method comprising:
receiving requests (<NUM>) to schedule queries (<NUM>) against a database (<NUM>) and scheduling execution of each one of the received queries (<NUM>) in a query schedule, where each one of the received queries a respective time for execution is scheduled;
receiving in an information retrieval data processing system (<NUM>), a request (<NUM>) to accelerate query execution of a specified query (<NUM>) of the received queries (<NUM>) to a time (<NUM>) prior to the scheduled time (<NUM>);
identifying in the specified query (<NUM>), a specific field (<NUM>) corresponding to data in the database (<NUM>);
retrieving a freshness of data requirement (<NUM>) for the specific field (<NUM>) and a frequency of change (<NUM>) the data corresponding to the specific field (<NUM>);
determining if execution of the specific query (<NUM>) at the time (<NUM>) prior to the scheduled time (<NUM>) instead of the scheduled time (<NUM>) violates the freshness of data requirement (<NUM>) based upon the frequency of change (<NUM>) of the data corresponding of the specific field (<NUM>); and
on condition that the execution of the specific query (<NUM>) is determined not to violate the freshness of data requirement (<NUM>) by scheduling the specific query (<NUM>) at the time (<NUM>) prior to the scheduled time (<NUM>), scheduling the specific query (<NUM>) for execution at the time (<NUM>) prior to the scheduled time (<NUM>), but otherwise maintaining the scheduled time (<NUM>) for executing the specific query (<NUM>).