Computer System and Database Management Method

• US 20180075080A1
• Filed: 07/17/2015
• Published: 03/15/2018
• Est. Priority Date: 07/17/2015
• Status: Active Grant

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: HANAI, Tomohiro, NISHIKAWA, Norifumi, SHIMIZU, Akira, MOGI, Kazuhiko
• Granted Patent: US 11,321,302 B2
• Time in Patent Office: Days
• CPC Class Codes: G06F 11/1471 involving logging of persistent data for recovery
• CPC Class Codes: G06F 16/2246 Trees, e.g. B+trees
• CPC Class Codes: G06F 16/2282 Tablespace storage structures; Management thereof
• CPC Class Codes: G06F 16/2358 Change logging, detection, and notification replication G06F16/27
• CPC Class Codes: G06F 9/4881 Scheduling strategies for dispatcher, e.g. round robin, multi-level priority queues
• CPC Class Codes: G06F 9/5016 the resource being the memory

Abstract

A computer system according to the present invention has a plurality of processor cores that execute a plurality of threads in a parallel manner. When one of the threads updates a database (DB) region that is among a plurality of database regions associated with a database (DB), and that cannot be updated by more than one thread, the computer system selects one of one or more dedicated log buffers as a log buffer to which a log relating to the update of the database region is to be written. In contrast, when one of the threads updates a database region that is among the plurality of database regions, and that can be updated by more than one thread, the computer system selects one of one or more shared log buffers as a log buffer to which a log relating to the update of the database region is to be written. Each dedicated log buffer is a log buffer that can store one or more logs associated with only one thread and that cannot store two or more logs associate with two or more threads. Each shared log buffer is a log buffer that can store two or more logs associated with two or more threads.

Claims

1. A computer system for managing a database, the computer system comprising:

a processor having a plurality of processor cores configured to execute a plurality of threads in parallel; and

a storage unit having one or more dedicated log buffers and one or more shared log buffers;

wherein the processor is configured to;

(A) select, for a thread that updates a database region from a plurality of database regions associated with the database and that cannot be updated by two or more threads, a dedicated log buffer as a log buffer to which a log relating to an update of the database region is to be written, and

(B) select, for a thread that updates a database region that is among the plurality of database regions and that can be updated by two or more threads, a shared log buffer as a log buffer to which a log relating to an update of the database region is to be written,

each dedicated log buffer is a log buffer that can store one or more logs associated with one thread but cannot store two or more logs associated with two or more threads, and

each shared log buffer is a log buffer that can store two or more logs associated with two or more threads.

2. The computer system according to claim 1, wherein:

each dedicated log buffer of a plurality of dedicated log buffers is allocated to a thread of the plurality of threads; and

the processor is configured to, in (A), select the dedicated log buffer allocated to the thread.

3. The computer system according to claim 2, wherein:

each shared log buffer of a plurality of shared log buffers is allocated to a thread of the plurality of threads; and

the processor is configured to, in (B), select a shared log buffer from the plurality of shared log buffers.

4. The computer system according to claim 3, wherein:

the database includes a table and an index;

the plurality of database regions include a plurality of data regions and a plurality of index regions;

each data regions of the plurality of data regions is a database region including data for a table;

each index regions of the plurality of index regions is a database region including data for an index; and

a database region that can be updated by two or more threads is an index region.

5. The computer system according to claim 4, wherein:

the shared log buffer selected in (B) is a shared log buffer selected based on an update target index region.

6. The computer system according to claim 5, wherein:

the index is a B-tree structured index composed of a tree-structured index region; and

in case that a split is performed with the index, the shared log buffer selected in (B) is a shared log buffer selected based on an upper index region connected to all of update target leaf index regions.

7. The computer system according to claim 6, wherein:

the upper index region is the uppermost index region among the all update target index regions.

8. The computer system according to claim 5, wherein:

the shared log buffer selected in (B) is a shared log buffer uniquely specified using a number of a target index region and a number of shared log buffers.

9. The computer system according to claim 4, wherein:

a plurality of log regions are allocated to the plurality of threads; and

each thread of the plurality of threads writes, logs in the a dedicated log buffer and a shared log buffer allocated to the thread to a log region allocated to the threads.

10. The computer system according to claim 4, wherein:

a thread is allocated to each of the plurality of data regions; and

a thread to which at least one data region is allocated is able to update the at least one data region allocated to it, but is unable to update a data region not allocated to it; and

each index region of the plurality of index regions is able to be updated by two or more threads.

11. The computer system according to claim 10, wherein:

each thread of the plurality of threads can update a data region and an index region; and

wherein the processor is configured to;

determine whether an update target database region is an index region;

execute, in the case that the result of the determination is negative, the process of (A); and

execute, in the case that the result of the determination is positive, the process of (B).

12. The computer system according to claim 1, wherein:

the processor is configured to acquire exclusivity of the selected shared log buffer and subsequently write a log to the selected shared log buffer in (B); and

the processor is configured to write a log in a dedicated log buffer corresponding to the thread when the processor cannot acquire exclusivity of the selected shared log buffer in (B).

13. A method for managing a database, the method comprising:

(A) selecting, for a thread that updates a database region from a plurality of database regions associated with the database and that cannot be updated by two or more threads, a dedicated log buffer as a log buffer to which a log relating to an update of the database region is to be written; and

(B) selecting, for a thread that updates a database region from a plurality of database regions and that can be updated by two or more threads, a shared log buffer as a log buffer to which a log relating to an update of the database region is to be written;

each dedicated log buffer is a log buffer that can store one or more logs associated with one thread but cannot store two or more logs associated with two or more threads; and

each shared log buffer is a log buffer that can store two or more logs associated with two or more threads.