JP2012247901A - Database management method, database management device, and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To quickly secure the memory zone of an in-memory-type database while effectively using a memory capacity used by a hybrid-type database.SOLUTION: In a database management method for a computer including a processor, memory and a storage device to control an in-memory DB and a disk DB, where the former DB stores a table and an index in a first memory zone of memory, and the latter DB stores a part of a table and an index that are stored in a second memory zone of the memory, the computer performs the steps of: selecting, when an event that the first memory zone of the in-memory DB is in shortage is detected, a target to be deleted from the table or index stored in the second memory zone of the disk DB; deleting the table or index selected as a target of deletion from the second memory zone; and releasing the zone of the table or index deleted from the second memory zone to add the released zone to the first memory zone.

Description

  The present invention relates to an in-memory database that arranges data on a main memory and a database that controls a storage database that arranges a part of data stored in a storage device in a buffer area on the main memory with a single database management system. About.

  Conventionally, data is stored in a storage device composed of a disk drive or the like, a buffer area (or cache area) is provided on the main memory of the computer, and data that the computer has received an access request is stored in a buffer area (hereinafter referred to as a DB buffer). Disk type (on-disk) databases (DB) that are reused or updated are widely used.

  In recent years, computers equipped with large-capacity memories are becoming widespread due to improvements in semiconductor manufacturing technology, etc., and in-memory databases that place data on main memory and perform high-speed access instead of storage devices are known. ing.

  On the other hand, disk-type databases using storage devices and DB buffers are also being considered for speeding up, and it is known that the DB buffer is divided into a plurality of areas and the division ratio is dynamically changed based on the response time to the request. (For example, Patent Document 1). In Patent Document 1, the DB buffer is divided into a plurality of areas, and the division ratio is determined so as to maintain the response time for each divided area.

  In the conventional in-memory database, since data is arranged on a finite main memory, the number and size of data to be handled are limited. For this reason, a hybrid database combining an in-memory database management unit and a disk database management unit has been proposed. In the hybrid database, data that is accessed at high speed is managed by the in-memory database, and a large amount of data that is not limited by the capacity of the main memory is managed by the legacy database.

JP 2005-327138 A

  However, in the conventional hybrid database, the database management system sets the area used by the in-memory database and the area of the DB buffer used by the disk database on the main memory. The database management system accesses the data by arranging an in-memory database area and a disk database DB buffer with the size of the area set on the main memory as an upper limit.

  If access is concentrated in the in-memory database, or if there is not enough space to add data to the table in the in-memory database, it is necessary to add the prepared area to the in-memory database area. There is.

  For this reason, in the conventional hybrid database, since the area used by the in-memory database is expanded, it is necessary to secure a storage area in the main memory in advance, and there is a problem that computer resources cannot be used effectively. It was.

  Therefore, the present invention is intended to quickly secure a memory area of an in-memory database even when the amount of data in the in-memory database increases while effectively utilizing the capacity of the main memory used by the hybrid database. Objective.

  The present invention provides a computer having an interface connected to a processor, a memory, and a storage device, an in-memory database that stores a table and an index in a first memory area on the memory, and a second memory on the memory A database management method for controlling a part of a table stored in the storage device and a disk database for storing an index in an area, wherein the computer has a first memory area of the in-memory database A first step of detecting an insufficiency; and when the computer detects an insufficiency of the first memory area, it is deleted from the table or index stored in the second memory area of the disk database A second step of selecting an object to be deleted, and a table selected by the computer as the object to be deleted. A third step of deleting the index from the second memory area, and the computer releases the table or index area deleted from the second memory area, and releases the released area to the first memory area. And a fourth step of adding to the memory area.

  Therefore, according to the present invention, the memory area used by the in-memory database can be quickly expanded when the data amount of the in-memory database increases while effectively using the memory capacity.

It is a block diagram which shows embodiment of this invention and shows an example of a computer system. It is a figure which shows embodiment of this invention and shows the outline | summary of the memory operation performed with a database management system. It is a flowchart which shows embodiment of this invention and shows an example of memory operation performed with a database management system. 4 is a flowchart illustrating an example of DB buffer release target determination processing performed in step S600 of FIG. 3 according to the embodiment of this invention. 6 is a flowchart illustrating an example of a release operation list calculation process performed in step S660 of FIG. 3 and steps S604 and S609 of FIG. 4 according to the embodiment of this invention. 4 is a flowchart illustrating an example of a DB buffer release operation performed in step S700 of FIG. 3 according to the embodiment of this invention. It is a figure which shows embodiment of this invention and shows an example of table | surface information. It is a figure which shows embodiment of this invention and shows an example of index information. It is a figure which shows embodiment of this invention and shows an example of memory area information. It is a figure which shows embodiment of this invention and shows an example of table access frequency information. It is a figure which shows embodiment of this invention and shows an example of DB buffer release object list. It is a figure which shows embodiment of this invention and shows an example of DB buffer release operation list.

  Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

  FIG. 1 is a block diagram showing an example of the configuration of a computer system that provides a hybrid database according to an embodiment of the present invention. The computer system includes a database management device 2100, a terminal device 2140 used by an administrator, a client terminal device 2160 used by a database user, and a network connecting the database management device 2100, the terminal device 2140, and the client terminal device 2160. 2150 and an external storage device 2200 that is connected to the database management device 2100 and stores data and programs.

  The database management device 2100 is composed of a computer having a processor 2102, a main storage device 2104, a network interface 2101, and an external storage device input / output interface 2103, and is a hybrid comprising an in-memory type database and a disk type (on-disk) database. Provides a type database.

  The network interface 2101 is connected to the network 2150 and communicates with the terminal device 2140 and the client terminal device 2160.

  The external storage device input / output interface 2103 is connected to the external storage device 2200, and reads / writes data and reads programs from / to the external storage device 2200 in response to a command from the processor 2102. The external storage device 2200 includes a storage device including a disk drive and a nonvolatile semiconductor storage device.

  The external storage device 2200 stores disk database data (table information 8010, index information 8020) 1001 provided by the database management device 2100, definition information of the in-memory database (or disk database), and the like. . Note that in-memory database data is stored in the external storage device 2200 while the database management device 2100 is stopped. The external storage device 2200 may be configured by a device such as NAS connected to the database management device 2100 via a network.

  The processor 2102 of the database management apparatus 2100 executes a database management system 2110 that provides an in-memory database and a disk (on-disk) database. The database management system 2110 is constituted by a program stored in a predetermined area (not shown) of the external storage device 2200, and is executed after the processor 2102 reads the program into the main storage device 2104. The external storage device 2200 also functions as a storage medium for storing the program of the database management system 2110.

  The database management system 2110 includes a memory area 2120 of an in-memory database, a buffer area (hereinafter referred to as a DB buffer) 2130 for inputting / outputting data of a disk database, and a table of the DB buffer 2130 on the main storage device 2104. Table / index information 8040 for managing data and indexes, and memory area information 8050 relating to the setting of the memory area 2120 of the in-memory database.

  In addition, on the main storage device 2104, a DB buffer release target list 8060 and a DB buffer release operation list 8070 generated when the database management system 2110 operates the DB buffer 2130 and the memory area 2120 of the in-memory database are held. The

  When activated, the database management system 2110 sets the memory area 2120 and the DB buffer 2130 of the in-memory database on the main storage device 2104 with a preset capacity or a capacity specified by the terminal device 2140.

  Then, the database management system 2110 reads from the external storage device 2200 a table 2121 preset in the memory area 2120 of the in-memory database or a table 2121 and an index 2122 designated from the terminal device 2140. If the access request from the UAP (User Application Program) executed by the client terminal device 2160 is an in-memory database, the memory area 2120 is accessed and the client terminal device 2160 is responded.

  In addition, the database management system 2110 operates a disk database, receives an access request from a UAP (User Application Program) of the client terminal device 2160, and when the access request target is a disk database, Table 2131 and For the index 2132, only a necessary part of the disk DB data 1001 of the external storage device 2200 is acquired and read into the DB buffer 2130. Then, the database management system 2110 processes a request from the client terminal device 2160 for the data read into the DB buffer 2130. The table 2131 and the index 2132 read into the DB buffer 2130 are a part of the disk DB data 1001 of the external storage device 2200.

  For the processing of data in which the hybrid database provided by the database management system 2110 responds to a request from the UAP of the client terminal device 2160, a known or well-known in-memory database and disk database processing may be applied.

  The operation of the DB buffer 2130 and the memory area 2120 of the in-memory database will be described later.

  The terminal device 2140 is a computer used by an administrator of the database management device 2100 and the like, and includes an input device and an output device. The client terminal device 2160 is a computer used by a hybrid database user and the like, and includes an input device and an output device.

<Software overview>
The database management system 2110 manages an in-memory database and a disk database. For this reason, the database management system 2110 includes a DB buffer management unit 2111 that manages the memory area 2120 of the in-memory database and the DB buffer 2130 of the disk database, and a DB buffer 2130 that can be released when the memory area 2120 is expanded. A DB buffer release target list 8060 for storing elements, and a DB buffer release operation list 8070 for storing elements of the DB buffer 2130 to be released from the DB buffer 2130 and added to the memory area 2120 of the in-memory database are provided.

  When the database management system 2110 receives an access request from the client terminal device 2160, the database management system 2110 determines whether the table to be accessed is an in-memory database or a disk database. When the table to be accessed is an in-memory database, the memory area 2120 of the in-memory database is accessed. The database management system 2110 accesses the DB buffer 2130 when the table to be accessed is a disk database.

  Upon receiving an access request to the in-memory database, the database management system 2110 searches the index 2122 or the table 2121 in the memory area 2120 to acquire data, and responds to the client terminal device 2160. In the example of FIG. 2, the in-memory type database shows an example in which the memory area 2120 has tables T1 and T3 and indexes corresponding to these tables arranged in the memory area 2120.

  On the other hand, when the database management system 2110 receives an access request for the disk database, the database management system 2110 searches the index 2132 or the table 2131 of the DB buffer 2130 or the external storage device 2200 to acquire data, and responds to the client terminal device 2160. As shown in FIG. 1, the external storage device 2200 stores disk DB data 1001 including a table 8010 and index 8020, which are data of a disk type database.

  The DB buffer management unit 2111 manages the table 2131 and the index 2132 read into the DB buffer 2130 and the memory area 2120 of the in-memory database. The DB buffer management unit 2111 needs the disk DB data 1001 to the table 2131 and the index 2132 of the external storage device 2200 when the part (record) of the table 2131 accessed by the database management system 2110 is not in the DB buffer 2130. The part is read and stored in the DB buffer 2130.

  At this time, the DB buffer management unit 2111 writes data that is no longer necessary in the DB buffer 2130 (a record or a part of an index constituting the table) to the external storage device 2200 or discards it. For determining the data that is no longer necessary, a known or publicly known method such as an LRU (Least Recently Used) method can be used. In the example of FIG. 2, the DB buffer management unit 2111 reads a part of the table T2 and the index corresponding to the table T2 from the disk DB data 1001 stored in the external storage device 2200 into the DB buffer 2130.

  Further, as will be described later, when the DB buffer management unit 2111 detects that the memory area 2120 of the in-memory type database is insufficient due to an increase in access to the in-memory type database or an increase in the table 2121, the DB buffer release target The determination unit 2112 and the DB buffer release operation execution unit 2113 are activated to reduce the DB buffer 2130. Then, the DB buffer management unit 2111 expands the memory area 2120 by allocating the capacity reduced from the DB buffer 2130 to the memory area 2120 of the in-memory database.

  The DB buffer management unit 2111 determines that the memory area 2120 is insufficient when the usage rate of the memory area 2120 of the in-memory database exceeds a preset threshold. Note that the threshold value can be stored in a capacity shortage detection ratio 8054 of the memory area information 8050 as shown in FIG.

  When it is determined that the memory area 2120 of the in-memory database is insufficient, the DB buffer release target determination unit 2112 determines an element (index) to be reduced from the DB buffer 2130 as described later. Then, the DB buffer release operation execution unit 2113 releases the determined element from the main storage device 2104 and adds it to the memory area 2120 of the in-memory database. As a result, the DB buffer management unit 2111 expands the memory area 2120 by adding the capacity (area) reduced from the DB buffer 2130 to the memory area 2120.

  When it is determined that there is a possibility that the memory area 2120 of the in-memory database is insufficient in the hybrid database including both the in-memory database and the disk database, the present invention The area used by the index 2132 and the like is reduced. Then, the area of the main storage device 2104 acquired from the index 2132 is added to the memory area 2120 of the in-memory database due to the reduction.

  By adding an area to the memory area 2120 of the in-memory database, the performance (for example, response) of the in-memory database is improved. On the other hand, the performance of the disk-type database decreases due to the reduction of the DB buffer 2130. Therefore, it is possible to improve the performance of the in-memory database while ensuring the performance of the entire hybrid database without preparing an expansion storage area in advance as in the conventional example. Thereby, a computer resource can be used effectively.

  That is, according to the present invention, the performance of the in-memory database is improved by extending the memory area 2120 of the in-memory database while reducing the performance of the disk database by reducing the index area of the DB buffer 2130. Maintain the overall performance of the hybrid database.

  In order to monitor the performance of the disk database and the in-memory database, the DB buffer management unit 2111 stores the table / index information 8040 regarding the elements of the DB buffer 2130 and the information regarding the memory area 2120 of the in-memory database as memory area information 8050. Are arranged on the main storage device 2104.

  As shown in FIG. 1, the table / index information 8040 includes table information 8041 that holds table information stored in the DB buffer 2130, and index information 8042 that holds information about indexes defined in the table of the table information 8041. And table access frequency information 8043 that holds the frequency of access to the table of the table information 8041.

  On the other hand, as shown in FIG. 9, the memory area information 8050 includes an in-memory DB capacity 8051 that holds the capacity allocated to the memory area 2120 of the in-memory database, and a threshold (ratio) for detecting signs of insufficient or insufficient capacity. ) For holding the capacity of the main storage device 2104 to be added to the memory area 2120, and a memory area expansion size 8053 for holding the capacity of the main storage device 2104 to be added to the memory area 2120. . Note that the threshold for detecting a shortage of capacity indicates an example of the ratio of the area actually being used with respect to the in-memory DB capacity 8051. In addition, the upper limit value of the capacity of the area that is actually in use may be set as the threshold value.

  The memory DB expansion ratio 8052 indicates a ratio of the capacity added to the memory area 2120 of the in-memory database in one operation, and this ratio stores a value multiplied by the in-memory DB capacity 8051. The memory area expansion size 8053 stores the memory DB expansion ratio 8052 in the in-memory DB capacity 8051.

  FIG. 7 is a diagram showing an example of the table information 8041 constituting the table / index information 8040.

  Table information 8041 includes a table ID 80411 for storing a table identifier, a table name 80412 for storing a table name, a definition index number 80413 for storing the number of indexes defined in the table, and a DB used by the table. One entry is configured from the DB buffer capacity 80414 for storing the capacity in the buffer and the reduction ratio 80415 for storing the ratio of the DB buffer capacity 80414 that can be reduced by one operation.

  FIG. 8 is a diagram showing an example of the index information 8042 constituting the table / index information 8040.

  The index information 8042 includes an index ID 80421 for storing an index identifier, an index name 80422 for storing an index name, a table ID 80423 for storing an identifier of a table referred to by the index, and whether or not the index is a secondary index. One entry is configured from the secondary index identification 80424 for identifying the above and the DB buffer capacity 80425 for storing the capacity on the DB buffer 2130 used by the index. If the secondary index identification 80424 is “1”, it indicates that the index is a secondary index, and if it is “0”, it indicates that it is a primary index.

  FIG. 9 is a diagram illustrating an example of memory area information 8050 for storing information related to the setting of the memory area 2120.

  The memory area information 8050 includes an in-memory DB capacity 8051 for storing the capacity of the memory area 2120 of the in-memory database, and an actual memory capacity 2120 for determining the shortage of the memory area 2120 of the in-memory database. Using the capacity ratio as the usage rate, the capacity shortage detection rate 8054 for storing this usage rate threshold, the memory DB expansion rate 8052 for storing the rate for expanding the memory region 2120, and the capacity for expanding the memory region 2120 are shown. Memory area expansion size 8053 to be stored.

  The memory DB expansion ratio 8052 stores in advance a ratio of expanding the memory area 2120 with respect to the capacity allocated to the in-memory database (in-memory DB capacity 8051). As the memory area expansion size 8053, the database management system 2110 stores a value obtained by multiplying the capacity of the area 2120 allocated to the in-memory database by the memory DB expansion ratio 8052.

  The contents of the memory area information 8050 may be input from the terminal device 2140 operated by an administrator or the like, or may be read and set by the database management system 2110 from a predetermined file.

  The table information 8041 and the index information 8042 in FIGS. 7 and 8 can be set and updated by the database management system 2110.

  FIG. 10 is a diagram showing an example of the table access frequency information 8043 constituting the table / index information 8040.

  The table access frequency information 8043 includes one entry including a table ID 80431 for storing a table identifier and an access frequency 80432 for storing the number of accesses to the table ID per day.

  The database management system 2110 updates the access frequency 80432 corresponding to the table ID 80431 of the table access frequency information 8043 every time access to the disk database is received in response to a request from the client terminal 2160 or the like.

  FIG. 11 is a diagram illustrating an example of the DB buffer release target list 8060 generated by the DB buffer release target determination unit 2112.

  The DB buffer release target list 8060 includes a release target type 8061 for storing the type of the element of the disk database to be released, a release target name 8062 for storing the name of the element to be released, and a release target. One entry is configured from the release size 8063 for storing the capacity of the element in the DB buffer 2130.

  FIG. 12 is a diagram illustrating an example of the DB buffer release operation list 8070 generated by the DB buffer release operation execution unit 2113.

  The DB buffer release operation list 8070 includes a release target 8071 for storing the name of the element of the disk database to be released, and a release capacity 8072 for storing the capacity on the DB buffer 2130 of the element to be released. One entry is configured.

<Outline of processing>
FIG. 2 shows that when the database management system 2110 of the present invention determines that the memory area 2120 of the in-memory database is insufficient, a part of the DB buffer 2130 of the disk-type database is reduced, and the reduced area is reduced to the in-memory type. It is a figure which shows the outline | summary of the memory operation expanded in addition to the memory area 2120 of a database.

  The DB buffer management unit 2111 of the database management system 2110 monitors the usage rate of the memory area 2120 of the in-memory database, and if the usage rate of the memory area 2120 exceeds a predetermined threshold (capacity shortage detection rate 8054), It detects that the memory area 2120 of the memory type database is insufficient.

  When the shortage of the memory area 2120 of the in-memory database is detected, the DB buffer management unit 2111 activates the DB buffer release target determination unit 2112 and starts the DB buffer release target determination process (S600) shown in FIG. The DB buffer release target determination process (S600) is a process performed by the DB buffer release target determination unit 2112 shown in FIG.

  In the DB buffer release target determination processing S600, the memory area expansion size 8053 is calculated from the in-memory DB capacity 8051 of the memory area information 8050 and the memory DB expansion ratio 8052. In this embodiment, an example in which the memory area 2120 of the in-memory database is expanded by one memory area expansion size 8053 by one expansion is shown.

  Next, the DB buffer release target determination unit 2112 reads the table information 8041, the index information 8042, and the table access frequency information 8043 from the table / index information 8040 in order to extract the elements of the disk-type database that are the targets of the memory reduction operation. . The DB buffer release target determination unit 2112 generates a DB buffer release target list 8060 from the read information as described later.

  The DB buffer release target determination unit 2112 refers to the DB buffer release target list 8060 and extracts the elements of the disk database until the capacity reaches the memory area expansion size 8053. Then, the DB buffer release target determination unit 2112 generates a DB buffer release operation list 8070 from the extracted disk database elements.

  When the processing of the DB buffer release target determination unit 2112 is completed, the DB buffer management unit 2111 activates the DB buffer release operation execution unit 2113 and executes the DB buffer release operation as described later (S700).

  The DB buffer release operation execution unit 2113 reads the DB buffer release operation list 8070, deletes the element of the disk database to be released from the DB buffer 2130, and writes it back to the external storage device 2200. The DB buffer release operation execution unit 2113 releases the area deleted from the DB buffer 2130. Then, the DB buffer release operation execution unit 2113 extends the memory area 2120 by adding the area released on the DB buffer 2130 to the memory area 2120 of the in-memory database (S800).

  Through the above processing, the database management system 2110 deletes some of the elements of the disk-type database from the DB buffer 2130 and adds them to the memory area 2120 of the in-memory database, so that the area of the main storage device 2104 can be used without waste. It is possible to prevent the in-memory database from running out of memory while being used.

<Details of processing>
The details of the processing performed by the database management system 2110 to reduce a part of the DB buffer 2130 of the disk type database and add the reduced storage area to the memory area 2120 of the in-memory type database will be described below.

  FIG. 3 is a flowchart showing an example of the overall processing of the memory operation performed by the database management system 2110. This process is executed at a predetermined cycle (for example, every minute).

  In step S200, the DB buffer management unit 2111 reads the memory area information 8050, monitors the area actually used in the in-memory DB capacity 8051, and the ratio of the area actually used is a threshold value. If a certain capacity shortage detection ratio 8054 is exceeded, it is detected that the memory area 2120 of the in-memory database is short (or a sign of shortage). If it is detected that the memory area 2120 is insufficient, the database management system 2110 activates the DB buffer release target determination unit 2112 and proceeds to step S300.

  In step S300, the DB buffer release target determination unit 2112 reads the memory area information 8050, multiplies the in-memory DB capacity 8051 by the memory DB expansion ratio 8052, and calculates the memory area expansion size 8053.

  In step S400, the DB buffer release target determination unit 2112 acquires the table information 8041 and the index information 8042 from the table / index information 8040, and identifies the table and index existing on the DB buffer 2130.

  In step S600, the DB buffer release target determination unit 2112 extracts the elements of the disk database to be DB buffer released from the table and index existing in the DB buffer 2130 by the process of FIG. An operation list 8060 is generated.

  In step S660, the DB buffer management unit 2111 calculates the total capacity (release capacity 8072) of the elements of the disk database constituting the DB buffer release operation list 8070 as the DB buffer release size.

  In step S690, the DB buffer management unit 2111 compares the memory area extension size 8053 obtained in step S300 with the DB buffer release size obtained in step S660, and determines whether the DB buffer release size is greater than or equal to the memory area extension size 8053. Determine whether or not. If the DB buffer release size is greater than or equal to the memory area expansion size 8053, the DB buffer management unit 2111 activates the DB buffer release operation execution unit 2113 and proceeds to step S700. On the other hand, if the DB buffer release size is less than the memory area expansion size 8053, the DB buffer management unit 2111 proceeds to step S692 and executes error processing for notifying that the memory area 2120 of the in-memory database cannot be expanded.

  In step S700, the DB buffer release operation execution unit 2113 deletes elements of the DB buffer release operation list 8070 from the DB buffer 2130 as shown in FIG.

  In step S800, the DB buffer release operation execution unit 2113 adds and expands the area deleted from the DB buffer 2130 in step S700 to the memory area 2120 of the in-memory database. The DB buffer release operation execution unit 2113 adds the memory area expansion size 8053 to the in-memory DB capacity 8051, and then clears the memory area expansion size 8053.

  Through the above processing, the element to be released is deleted from the DB buffer 2130, and the deleted area is added to the memory area 2120 of the in-memory database.

<DB buffer release target decision processing>
FIG. 4 is a flowchart showing an example of the DB buffer release target determination process performed in step S600 of FIG.

  In step S601, the DB buffer release target determination unit 2112 generates the DB buffer release target list 8060 shown in FIG. 11 from the table and index acquired in step S400 of FIG. Next, the DB buffer release target determination unit 2112 reads the table access frequency information 8043 shown in FIG. 10 and sorts the DB buffer release target list 8060 in ascending order of the access frequency 80432. At this time, if the release target type 8061 is a table, the access frequency information 8043 corresponding to the identifier of the table included in the release target name 8062 is used. When the release target type 8061 is an index, the identifier of the table included in the release target name 8062 may be handled as the access frequency information 8043 of the index.

  In step S602, the DB buffer release target determination unit 2112 repeats the processing in steps S603 to S606 from the top entry of the DB buffer release target list 8060 generated in step S601.

  In step S603, the DB buffer release target determination unit 2112 reads the entries in the DB buffer release target list 8060 in ascending order of the access frequency 80432 in step S601. Then, the DB buffer release target determination unit 2112 determines whether or not the release target type 8061 of the entry in the stored DB buffer release target list 8060 is “index”. If it is “index”, the DB buffer release target determination unit 2112 searches the index name 80422 and the table ID 80423 of the index information 8042 of FIG. 8 using the release target name 8062, and acquires the secondary index identification 80424 of the index.

  The DB buffer release target determination unit 2112 determines whether or not the secondary index identification 80424 is “1”. If it is “1”, the release target name 8062 is secondary, so the release target name 8062. Thus, an entry is added to the DB buffer release operation list 8070. That is, the DB buffer release target determination unit 2112 sets the release target name 8062 as the release target 8071 of the DB buffer release operation list 8070, and acquires the capacity used by the secondary index from the DB buffer capacity 80425 of the index information 8042. This capacity is set in the release capacity 8072 of the DB buffer release operation list 8070.

  In step S604, the DB buffer release target determination unit 2112 calculates the sum of the secondary index capacities (release capacity 8072) added to the DB buffer release operation list 8070 as the DB buffer release size.

  In step S605, the DB buffer release target determination unit 2112 compares the memory area extension size 8053 obtained in step S300 with the DB buffer release size obtained in step S604, and the DB buffer release size is equal to or larger than the memory area extension size 8053. It is determined whether or not.

  If the DB buffer release size is equal to or larger than the memory area expansion size 8053, the DB buffer release target determination unit 2112 ends the processing of FIG. 4 because the area to be reduced from the DB buffer 2130 is equal to or larger than the memory area expansion size 8053. Returning to the process of FIG.

  On the other hand, if the DB buffer release size is less than the memory area expansion size 8053, the DB buffer release target determination unit 2112 returns to Step S603 and repeats the above processing for the next entry in the DB buffer release target list 8060 (S606).

  The DB buffer release target determination unit 2112 proceeds to step S806 if the DB buffer release size is less than the memory area expansion size 8053 even when processing is completed for all entries in the DB buffer release target list 8060. That is, in the DB buffer release operation list 8070 for only the secondary index that is currently generated, the DB buffer release size does not reach the required memory area expansion size 8053.

  In step S607, the DB buffer release target determination unit 2112 repeats the processes in steps S608 to S611 from the top entry of the DB buffer release target list 8060 generated in step S601. The DB buffer release target list 8060 is sorted in ascending order of access frequency as described above.

  In step S608, the DB buffer release target determination unit 2112 reads the entries in the DB buffer release target list 8060 in ascending order of the access frequency 80432 in step S601. Then, the DB buffer release target determination unit 2112 determines whether or not the release target type 8061 of the entry in the stored DB buffer release target list 8060 is “table”. If it is “table”, the DB buffer release target determination unit 2112 searches the table ID 80411 of the table information 8041 of FIG. 7 using the release target name 8062, the reduction ratio 80415 of the table, and the DB buffer used by the table The capacity 80414 is acquired. The DB buffer release target determination unit 2112 obtains a value obtained by multiplying the DB buffer capacity 80414 in use by the table by the reduction ratio 80415 as the release capacity.

  The DB buffer release target determination unit 2112 adds an entry to the DB buffer release operation list 8070 with the release target name 8062 of the table. That is, the DB buffer release target determination unit 2112 sets the release target name 8062 of the table as the release target 8071 of the DB buffer release operation list 8070, and releases the capacity obtained from the reduction ratio 80415 to the release of the DB buffer release operation list 8070. The capacity is set to 8072. The reduction ratio 80415 is 30%, for example, as shown in FIG. 7, and when the DB buffer capacity 80414 in use is, for example, 300 MB, the release capacity 8072 is 90 Mbytes. The release capacity 8072 of the table in the DB buffer release operation list 8070 indicates the capacity to be written back to the external storage device 2200 in the area where the table of the release target 8071 is in use by the DB buffer 2130.

  In step S609, the DB buffer release target determination unit 2112 calculates the total of the release capacity 8072 including the table added to the DB buffer release operation list 8070 as the DB buffer release size.

  In step S610, the DB buffer release target determination unit 2112 compares the memory area extension size 8053 obtained in step S300 with the DB buffer release size obtained in step S608, and the DB buffer release size is equal to or larger than the memory area extension size 8053. It is determined whether or not.

  If the DB buffer release size is equal to or larger than the memory area expansion size 8053, the DB buffer release target determination unit 2112 ends the processing of FIG. 4 because the area to be reduced from the DB buffer 2130 is equal to or larger than the memory area expansion size 8053. Returning to the process of FIG.

  On the other hand, if the DB buffer release size is less than the memory area expansion size 8053, the DB buffer release target determination unit 2112 returns to step S607 and repeats the above processing for the next entry in the DB buffer release target list 8060 (S611).

  The DB buffer release target determination unit 2112 extracts the secondary index from the DB buffer 2130 to the DB buffer release operation list 8070 by the processing of FIG. 4, and if the DB buffer release size is less than the memory area expansion size, A predetermined reduction rate 80415 is reduced from the table in use of the buffer 2130 and added to the DB buffer release operation list 8070.

<DB buffer release operation list calculation process>
FIG. 5 is a flowchart showing an example of calculation processing of the DB buffer release operation list 8070 performed in step S660 of FIG. 3 and steps S604 and S609 of FIG.

  The DB buffer release target determination unit 2112 or the DB buffer management unit 2111 reads the entries from the beginning to the end of the DB buffer release operation list 8070 by repeating steps S661, S662, and S663, and sets the sum of the release capacity 8072 to the DB. Calculated as buffer release size.

<DB buffer release operation execution processing>
FIG. 6 is a flowchart showing an example of the DB buffer release operation execution process performed in step S700 of FIG.

  In step S711, the DB buffer release operation execution unit 2113 reads the DB buffer release operation list 8070. In step S712, the DB buffer release operation execution unit 2113 repeats the processing in steps S713 to S716 for the entries from the beginning to the end of the DB buffer release operation list 8070.

  In step S713, the DB buffer release operation execution unit 2113 reads one entry from the release operation list 8070, and acquires the release target 8071 and the release capacity 8072.

  In step S 714, the DB buffer release operation execution unit 2113 writes the read release target 8071 back into the disk DB data 1001 of the external storage device 2200. At this time, when the DB buffer release operation execution unit 2113 writes back a part of the DB buffer 2130 to the external storage device 2200, the target to be written back can be determined by a known or known method such as LRU (Least Recently Used). Good.

  Note that the DB buffer release operation execution unit 2113 may delete the read release target 8071 without writing back to the external storage device 2200 when the read target 8071 is a secondary index.

  In step S715, the DB buffer release operation execution unit 2113 releases the area on the DB buffer 2130 used by the release target 8071. At this time, when the release target 8071 is “table”, the DB buffer release operation execution unit 2113 subtracts a value obtained by multiplying the DB buffer capacity 80414 by the reduction ratio 80415 from the DB buffer capacity 80414 in use by the table. The buffer capacity 80414 is updated. When the release target 8071 is “index”, the DB buffer release operation execution unit 2113 deletes the corresponding index ID 80421 or index name 80422 entry from the index information 8042. Alternatively, when a part of the index is released, the DB buffer capacity 80425 in use of the index information 8042 may be updated.

  When the processes in steps S713 to S714 are completed for all entries in the DB buffer release operation list 8070, the process proceeds to step S720. In step S720, the DB buffer release operation execution unit 2113 deletes and initializes all entries in the DB buffer release operation list 8070. Also, the DB buffer release operation execution unit 2113 updates the in-memory DB capacity 8051 of the memory area information 8050 by adding the DB buffer release size obtained in step S660 of FIG. In addition, the DB buffer release operation execution unit 2113 clears the memory area expansion size 8053 of the memory area information 8050.

  Through the above processing, the disk database element added to the DB buffer release operation list 8070 is written back to the external storage device 2200, and the area used on the DB buffer 2130 is released.

<Summary>
As described above, in the present invention, when the actual usage amount of the memory area 2120 of the in-memory database exceeds the threshold (capacity shortage detection ratio 8054), the DB buffer management unit 2111 runs out of the memory area of the in-memory database. Or detect signs of shortage.

  When the shortage of the memory area 2120 is detected, the DB buffer management unit 2111 reduces the capacity of the DB buffer 2130 and adds it to the memory area 2120 of the in-memory database, so that the resources of the main storage device 2104 can be used without waste. The performance of the in-memory database can be secured while being used.

  The DB buffer management unit 2111 holds a unit (ratio) for expanding the memory area 2120 of the in-memory database as a memory DB expansion ratio 8052 of the memory area information 8050. Then, every time the memory area 2120 is expanded, the DB buffer release target determining section 2112 of the DB buffer management section 2111 multiplies the current capacity 8051 of the memory area 2120 by the memory DB expansion ratio 8052 to add the memory area expansion to be added this time. The size 8053 is obtained.

  The DB buffer release target determination unit 2112 first adds secondary indexes to the DB buffer release operation list 8070 as release targets in ascending order of access frequency. Then, the DB buffer release target determining unit 2112 externally writes a part of the table on the DB buffer 2130 back to the external storage device 2200 when the total capacity of the secondary indexes to be released is less than the memory area expansion size 8053. After instructing the storage device input / output interface 2103, a part of the table is deleted. Here, in the table information 8041, a ratio of writing back from the DB buffer 2130 by one reduction operation for each table ID 80411 is set in advance as a reduction ratio 80415. Then, the DB buffer release target determination unit 2112 satisfies the memory area expansion size 8053 for processing to sequentially determine the release capacity 8072 from the DB buffer release target list 8060 in the order of low access frequency and add it to the DB buffer release operation list 8070. Repeat until.

  By such processing, first, the secondary indexes are deleted from the DB buffer 2130 in the order of low access frequency, and further, a part of the table is deleted at a predetermined ratio in the order of low access frequency to release the area of the DB buffer 2130. be able to. The data to be deleted is written back to the external storage device 2200.

  Then, by adding the area released from the DB buffer 2130 to the memory area 2120 of the in-memory database, the necessary area for the in-memory database can be quickly secured while using the resources of the main memory 2104 without waste. It becomes possible to do.

  In the above-described embodiment, an example in which a part of a table with low access frequency is written back to the external storage device 2200 is shown. However, all of a table with low access frequency may be written back to the external storage device 2200.

  In the above embodiment, the secondary index is added to the DB buffer release operation list 8070 in ascending order of access frequency. However, the hit rate using the secondary index is monitored, and the secondary index with the low hit rate is assigned to the DB buffer 2130. You may make it delete from.

  In the above embodiment, the database is stored in the external storage device 2200. However, the database may be stored in a storage device or a storage device in the database management device 2100.

  In the above-described embodiment, the table or index of the DB buffer release operation list 8070 is written back to the external storage device 2200. However, the table or index of the DB buffer release operation list 8070 is stored in the storage device of the database management device 2100. You may make it move.

  In the above-described embodiment, an example in which a part of the DB buffer 2130 is released and added to the memory area 2120 when the memory area 2120 of the in-memory database is insufficient or an indication of a shortage has been shown. A part of the DB buffer 2130 may be released and added to the memory area 2120 when the 2110 receives a command to add data in the table of the in-memory database.

The present invention can be applied to a computer that provides a hybrid database having an in-memory database and a disk database.

2100 Database management device 2102 Processor 2103 External storage device input / output interface 2104 Main storage device 2110 Database management system 2111 DB buffer management unit 2112 DB buffer release target determination unit 2113 DB buffer release operation execution unit 2120 Memory area 2130 DB buffer 2200 External storage device 8040 Table / index information 8050 Memory area information

Claims (13)

A computer having an interface connected to a processor, a memory, and a storage device, an in-memory database that stores a table and an index in a first memory area on the memory, and the storage in a second memory area on the memory A database management method for controlling a part of a table stored in a device and a disk type database for storing an index,
A first step in which the computer detects that the first memory area of the in-memory database is insufficient;
A second step of selecting a target to be deleted from a table or index stored in the second memory area of the disk-type database when the computer detects that the first memory area is insufficient;
A third step in which the computer deletes the table or index selected as the object to be deleted from the second memory area;
A fourth step in which the computer releases a table or index area deleted from the second memory area and adds the released area to the first memory area;
A database management method comprising: A database management method according to claim 1, comprising:
The second step includes
A fifth step in which the calculator calculates a size of an area to be added to the first memory area as an extended size;
A sixth step of sequentially selecting a table or index stored in the second memory area in a predetermined order as a target to be deleted; and
A database management method, wherein the sixth step is repeated until the total capacity of the tables or indexes selected as the deletion target becomes equal to or larger than the extension size. A database management method according to claim 2, comprising:
The second step includes
Including a seventh step of obtaining an access frequency to the table of the disk-type database;
The sixth step includes
A database management method, wherein the table or index is sequentially selected as the deletion target in the order of low access frequency. A database management method according to claim 2, comprising:
The sixth step includes
A database management method comprising: selecting a secondary index as a deletion target when a secondary index exists in the index stored in the second memory area. A database management method according to claim 2, comprising:
The sixth step includes
A deletion ratio is preset for each table, tables stored in the second memory area are selected in the predetermined order, and the deletion ratio is set to a capacity used by the selected table in the second memory area. A database management method, wherein the multiplied capacity is selected as a deletion target. A database management method according to claim 1, comprising:
The third step includes
A database management method, comprising: transmitting an instruction for moving a table or an index selected as an object to be deleted to the storage apparatus to the interface. A processor, a memory, and an interface connected to the storage device;
An in-memory database that stores tables and indexes in a first memory area on the memory;
A disk-type database for storing a part of a table and an index stored in the storage device in a second memory area on the memory;
A management unit for controlling the in-memory database and the disk-type database;
A database management device comprising:
The management unit
An object determination unit that selects an object to be deleted from a table or index stored in the second memory area of the disk-type database when it is detected that the first memory area of the in-memory database is insufficient;
The table or index selected as the object to be deleted is deleted from the second memory area, the table or index area deleted from the second memory area is released, and the released area is released from the first memory area. A release execution unit to be added to the memory area of
A database management apparatus comprising: The database management device according to claim 7,
The target determining unit
The size of the area to be added to the first memory area is calculated as an extended size, and the second size is added in a predetermined order until the total capacity of the table or index selected as the deletion target is equal to or larger than the extended size. A database management apparatus that sequentially selects a table or an index stored in a memory area as an object to be deleted. The database management apparatus according to claim 8, wherein
The target determining unit
An apparatus for managing a database, comprising: obtaining an access frequency to a table of the disk-type database, and sequentially selecting the table or index as the object to be deleted in order of increasing access frequency. The database management apparatus according to claim 8, wherein
The target determining unit
A database management apparatus, wherein when a secondary index exists in an index stored in the second memory area, the secondary index is selected as a deletion target. The database management apparatus according to claim 8, wherein
The target determining unit
A deletion ratio is preset for each table, tables stored in the second memory area are selected in the predetermined order, and the deletion ratio is set to a capacity used by the selected table in the second memory area. A database management apparatus that selects a multiplied capacity as a deletion target. The database management device according to claim 7,
The release execution unit
A database management apparatus, wherein a command for moving a table or an index selected as a deletion target to the storage apparatus is transmitted to the interface. A computer having an interface connected to a processor, a memory, and a storage device, an in-memory database that stores a table and an index in a first memory area on the memory, and the storage in a second memory area on the memory A database program for controlling a part of a table stored in a device and a disk type database for storing an index,
A first procedure for detecting that the first memory area of the in-memory database is insufficient;
A second procedure for selecting an object to be deleted from a table or index stored in the second memory area of the disk-type database when it is detected that the first memory area is insufficient;
A third procedure for deleting the table or index selected as the object to be deleted from the second memory area;
A fourth procedure for releasing a table or index area deleted from the second memory area and adding the released area to the first memory area;
Is executed by the computer.

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