Patent Publication Number: US-2023153306-A1

Title: Offloading data interfacing method between dbms storage engine and computational storage device

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) AND CLAIM OF PRIORITY 
     This application is based on and claims priority under 35 U.S.C. § 119 to Korean Patent Application No. 10-2021-0156265, filed on Nov. 15, 2021, in the Korean Intellectual Property Office, the disclosure of which is herein incorporated by reference in its entirety. 
     BACKGROUND 
     Field 
     The disclosure relates to a database (DB) system, and more particularly, to a processing data interfacing method between a database management system (DBMS) and a storage in an environment where the DBMS and the storage in which a DB is established are disaggregated. 
     Description of Related Art 
     In a query execution process, a database management system (DBMS) may acquire data by scanning a query in a database (DB), filter the acquired data, and return only the filtered data to a client. 
     However, when there are many data to be scanned in the DB, many data are transmitted from a storage in which the DB is established to the DBMS, and accordingly, there are problems that a bandwidth becomes scarce and an overall response speed is reduced, and power consumption increases. 
     As a solution to these problems, there is a method of implementing the storage of the DB by using a computational storage drive (CSD), and allowing the storage to perform a part of the query computations. However, a specific method to achieve this has not yet been proposed. 
     SUMMARY 
     The disclosure has been developed to address the above-discussed deficiencies of the prior art, and an object of the present disclosure is to provide a method of defining a snippet for offloading a part of query computations in a DB system using a CSD, and interfacing a DBMS and a storage by using an offloading snippet. 
     According to an embodiment of the disclosure to achieve the above-described object, a query offloading method may include: a step of receiving, by a DBMS, a query execution request from a client; a step of generating, by the DBMS, an offloading code which is a code for offloading a part of the query computations, based on the received query; and a step of delivering, by the DBMS, the offloading code to a storage in which a DB is established in a CSD. 
     According to an embodiment of the disclosure, the query offloading method may further include a step of determining, by the DBMS, whether to offload a part of query computations, and the step of generating may be performed when offloading is determined at the step of determining. 
     The step of determining may include determining by determining which is appropriate, the DBMS processing all of the query computations, or the storage processing a part of the query computations and the DMBS processing the other query computations. 
     The step of determining may include determining to offload a part of the query computations when there is a large amount of data transmitted between the DBMS and the storage. 
     According to an embodiment of the disclosure, the query offloading method may further include: a step of receiving, by the CSD of the storage, the offloading code from the DBMS; a step of checking, by the CSD, validity of the received offloading code, and parsing; a step of reading out, by the CSD, data from the DB by scanning the query recorded on the offloading code; a step of filtering, by the CSD, the read-out data; and a step of returning, by the CSD, the filtered data to the DBMS. 
     The step of returning may further include: a step of checking, by the CSD, validity of the filtered data; a step of checking, by the CSD, validity of a buffer address recorded on the offloading code; a step of converting, by the CSD, the filtered data into a Json type; and a step of storing, by the CSD, the filtered and converted data in a buffer indicated by the buffer address. 
     The step of storing may include moving the data from a buffer of the CSD to a buffer indicated by the buffer address in a remote DMA method without passing through a CPU of the CSD. The buffer indicated by the buffer address may be a buffer of the DBMS. 
     The offloading code may be generated as a snippet, and may include a parsed query and a buffer address of the DBMS. 
     According to another embodiment of the disclosure, a DB system may include: a storage in which a DB is established in a CSD; and a DBMS configured to generate an offloading code which is a code for offloading a part of query computations, based on a received query, when a query execution request is received from a client, and to deliver the offloading code to the storage. 
     According to still another embodiment of the disclosure, a query offloading method may include: a step of generating, by a DBMS, an offloading code which is a code for offloading a part of query computations, based on a query; a step of delivering, by the DBMS, the offloading code to a storage in which a DB is established in a CSD; and a step of receiving, by the DBMS, a result of executing the offloading code from the CSD. 
     According to yet another embodiment of the disclosure, a DB system may include: a storage in which a DB is established in a CSD; and a DBMS configured to generate an offloading code which is a code for offloading a part of query computations, based on a query, to deliver the offloading code to the storage; and to receive a result of executing the offloading code from the CSD. 
     According to embodiments of the disclosure as described above, in a DB system using a CSD, a snippet for offloading a part of query computations may be defined, and a DBMS and a storage are interfaced by using the offloading snippet, so that a guideline for execution of a query by interworking between the CSD-based storage and the DBMS is provided. 
     In addition, according to embodiments of the disclosure, an RDMA connection interface between the DBMS and the CSD is supported, so that a data transmission speed for an offloading processing process is maximized and a query execution time is reduced. 
     Other aspects, advantages, and salient features of the invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses exemplary embodiments of the invention. 
     Before undertaking the DETAILED DESCRIPTION OF THE INVENTION below, it may be advantageous to set forth definitions of certain words and phrases used throughout this patent document: the terms “include” and “comprise,” as well as derivatives thereof, mean inclusion without limitation; the term “or,” is inclusive, meaning and/or; the phrases “associated with” and “associated therewith,” as well as derivatives thereof, may mean to include, be included within, interconnect with, contain, be contained within, connect to or with, couple to or with, be communicable with, cooperate with, interleave, juxtapose, be proximate to, be bound to or with, have, have a property of, or the like. Definitions for certain words and phrases are provided throughout this patent document, those of ordinary skill in the art should understand that in many, if not most instances, such definitions apply to prior, as well as future uses of such defined words and phrases. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a more complete understanding of the present disclosure and its advantages, reference is now made to the following description taken in conjunction with the accompanying drawings, in which like reference numerals represent like parts: 
         FIG.  1    is a view illustrating a DB system according to an embodiment of the disclosure; 
         FIG.  2    is a view illustrating a structure of the DBMS shown in  FIG.  1   ; 
         FIG.  3    is a view illustrating a structure of a query computation offloading snippet; 
         FIG.  4    is a view illustrating a structure of the storage node shown in  FIG.  1   ; 
         FIG.  5    is a view illustrating a structure of the CSD shown in  FIG.  4   ; 
         FIG.  6    is a view illustrating operations of the output layer shown in  FIG.  5    in detail; 
         FIG.  7    is a view illustrating a path through which a result of executing a query computation offloading snippet is returned; and 
         FIG.  8    is a view conceptually illustrating a remote direct memory access (RDMA) channel. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, the disclosure will be described in detail with reference to the accompanying drawings. 
     An embodiment of the disclosure provides a method for defining a snippet for offloading (pushing down) a part of query computations onto a CSD in a DB system using the CSD, and processing query computations by a DBMS and a storage interworking with each other by using the snippet. 
       FIG.  1    is a view illustrating a DB system according to an embodiment of the disclosure. The DB system according to an embodiment of the disclosure may be divided into a DBMS  100  and a plurality of storage nodes  200 - 1 ,  200 - 2 , . . . ,  200 - n  as shown in the drawing. 
     The storage nodes  200 - 1 ,  200 - 2 , . . . ,  200 - n  refer to storage systems in which the same DB is established. The plurality of storage nodes  200 - 1 ,  200 - 2 , . . . ,  200 - n  may be implemented in order to process many queries which are requested simultaneously. 
     Furthermore, the storage nodes  200 - 1 ,  200 - 2 , . . . ,  200 - n  include a computation function, and may perform a part of query computations. 
     The DBMS  100  is a system that executes a query according to a request of a client (not shown) and returns a result thereof. All of the query computations may be performed by the DBMS  100 , but a part of the query computations may be offloaded onto the storage nodes  200 - 1 ,  200 - 2 , . . . ,  200 - n.    
       FIG.  2    is a view illustrating a structure of the DBMS  100  shown in  FIG.  1   . As shown in the drawing, the DBMS  100  may include a query engine  110 , a storage engine  120 , and a remote direct memory access (RDMA) manager  130 . 
     Upon receiving a query execution request from a client, the query engine  110  may optimize the received query and deliver the same to the storage engine  120 . 
     The storage engine  120  may determine whether to offload query computations. Offloading query computations may refer to offloading a part of the query computations onto the storage nodes  200 - 1 ,  200 - 2 , . . . ,  200 - n . A part of the query computations may include query scanning, filtering, and validation. 
     It may be determined whether the query computations are offloaded by determining whether it is appropriate for the query engine  110  to execute all of the query computations, or whether it is appropriate for the storage nodes  200 - 1 ,  200 - 2 , . . . ,  200 - n  to execute a part of the query computations, and for the query engine  110  to execute the other query computations. 
     When there is a large amount of data transmitted between the DBMS  100  and the storage nodes  200 - 1 ,  200 - 2 , . . . ,  200 - n  in executing the query, that is, when there are many data to be scanned, offloading the query computations may be appropriate, but in other cases, offloading the query computations may be inappropriate. 
     The storage engine  120  generates a query computation offloading snippet based on the query, and delivers the generated query computation offloading snippet to the RDMA manager  130 . 
     The query computation offloading snippet generated by the storage engine  120  is a source code for offloading a part of the query computations onto the storage node  200 - 1 ,  200 - 2 , . . . ,  200 - n , and a detailed structure thereof is illustrated in  FIG.  3   . 
     As shown in the drawing, the query computation offloading snippet includes ParsedQuery, TableSchema, BlockOffset, and BufferAddress. The ParsedQuery may include a Select statement and a Where clause. The BufferAddress refers to an address of a buffer (not shown) that stores a result of performing a part of the query computations according to the query computation offloading snippet. The buffer is provided in the RDMA manager  120 . 
     The RDMA manager  130  delivers the query computation offloading snippet generated by the storage engine  120  to the storage nodes  200 - 1 ,  200 - 2 , . . . ,  200 - n , and receives a result of performing the query computation offloading snippet from the storage nodes  200 - 1 ,  200 - 2 , . . . ,  200 - n  and delivers the result to the storage engine  120 . 
       FIG.  4    is a view illustrating a structure of the storage nodes  200 - 1 ,  200 - 2 , . . . ,  200 - n  shown in  FIG.  1   . Since the storage nodes  200 - 1 ,  200 - 2 , . . . ,  200 - n  may be implemented in the same way, only one storage node  200  is illustrated in  FIG.  4    as a representative by using reference numeral “ 200 .” 
     As shown in the drawing, the storage node  200  may include a storage I/O interface  210  and a plurality of CSDs  220 - 1 ,  220 - 2 ,  220 - 3 . 
     The storage I/O interface  210  may be an interface for communicating with the DBMS  100 , and, when a query computation offloading snippet is delivered from the RDMA manager  130  of the DBMS  100 , the storage I/O interface  210  may deliver the query computation offloading snippet to one of the CSDs  220 - 1 ,  220 - 3 ,  220 - 3 . 
     The CSDs  220 - 1 ,  220 - 2 ,  220 - 3  include not only storage resources for storing a DB, but also CPU resources (for example, a CSD runtime in  FIG.  4   ) for performing a part of query computations. 
       FIG.  5    is a view illustrating a structure of the CSDs  220 - 1 ,  220 - 2 ,  220 - 3  shown in  FIG.  4   . Since the CSDs  220 - 1 ,  220 - 2 ,  220 - 3  may be implemented in the same way, only one CSD  220  is illustrated in  FIG.  5    as a representative by using reference numeral “ 220 .” 
     As shown in the drawing, the CSD  220  includes an input layer  221 , a scan layer  222 , a filter layer  223 , and an output layer  224 . 
     The input layer  221  checks validity of a query computation offloading snippet received from the RDMA manager  130  of the DBMS  100 , and then parses the snippet. The scan layer  222  reads out data stored in a storage drive by performing query scanning. 
     The filter layer  223  filters a result of scanning by the scan layer  222 . The output layer  224  returns the data filtered by the filter layer  223  to the RDMA manager  130  of the DBMS  100 . 
       FIG.  6    is a view illustrating operations of the output layer  224  in detail. As shown in  FIG.  6   , a filter data validator of the output layer  224  may check validity regarding the data filtered by the filter layer  223  ( 1 ), and a buffer address validator of the output layer  224  may check validity on a buffer address parsed in the query computation offloading snippet and may store the data in the data buffer of the output layer  224  ( 2 ). 
     Next, a Json converter of the output layer  224  may convert the filtered data which is validated into a Json type ( 3 ), and an API manager of the output layer  224  may store the converted data in a buffer of the RDMA manager  130  ( 4 ). A buffer address of the RDMA  130  is designated by BufferAddress. 
     As described above, the filtered data may be directly returned by the output layer  224  in an RDMA method without intervention by a CPU.  FIG.  7    illustrates a path through which filtered data, that is, a result of executing a query calculation offloading snippet, is returned. 
     As shown in the drawing, the result of executing the query computation offloading snippet by the CSDs  220 - 1 ,  220 - 2 ,  220 - 3  may be directly delivered to a receiver of the RDMA manager  130  connected via an RDMA channel without passing through the CPU, and may be stored in a data buffer of the RDMA manager  130 . The result stored in the data buffer may be delivered to the query engine  110  through the storage engine  120 . 
       FIG.  8    is a view conceptually illustrating an RDMA channel. As shown in the drawing, the RDMA manger  130  directly delivers a query computation offloading snippet to the CSDs  220 - 1 ,  220 - 2 ,  220 - 3  through a network adapter by using an RDMA server, which functions as a sender, and directly receives a result of processing the snippet from the CSDs  220 - 1 ,  220 - 2 ,  220 - 3  through the network adapter by using an RDMA client, which functions as a receiver, and may store the result in the data buffer. 
     Up to now, a method for defining a snippet for offloading a part of query computations to a CSD in a DB system using the CSD, and processing query computations by a DBMS and a storage interworking with each other by using the snippet have been described in detail with reference to preferred embodiments. 
     Specifically, in an embodiment of the disclosure, a query computation offloading snippet is proposed as a structure for offloading a part of query computations from a DMBS onto a storage when the storage is implemented by using a CSD in a cloud-native environment, in which the DBMS and the storage are disaggregated. 
     In addition, an RDMA connection interface between the DBMS and the CSD is supported, so that a data transmission speed for an offloading processing process is maximized and a query execution time is reduced. 
     The technical concept of the disclosure may be applied to a computer-readable recording medium which records a computer program for performing the functions of the apparatus and the method according to the present embodiments. In addition, the technical idea according to various embodiments of the present disclosure may be implemented in the form of a computer readable code recorded on the computer-readable recording medium. The computer-readable recording medium may be any data storage device that can be read by a computer and can store data. For example, the computer-readable recording medium may be a read only memory (ROM), a random access memory (RAM), a CD-ROM, a magnetic tape, a floppy disk, an optical disk, a hard disk drive, or the like. A computer readable code or program that is stored in the computer readable recording medium may be transmitted via a network connected between computers. 
     In addition, while preferred embodiments of the present disclosure have been illustrated and described, the present disclosure is not limited to the above-described specific embodiments. Various changes can be made by a person skilled in the art without departing from the scope of the present disclosure claimed in claims, and also, changed embodiments should not be understood as being separate from the technical idea or prospect of the present disclosure.