Database management system and method

Patent metadata

Field	Value
Publication number	US-2016125018-A1
Application number	US-201414894042-A
Country	US
Kind code	A1
Filing date	Jan 22, 2014
Priority date	Jan 22, 2014
Publication date	May 5, 2016
Grant date	—

Abstract

A database management system generates a log each transaction during execution of a plurality of transactions and stores the generated logs in log storage areas. The database management system records sequence numbers of logs at least in the generated logs of transactions belonging to a set of transactions of which results are different depending on a transaction execution order.

First claim

1 . A database management system for managing a database, comprising:
a query receiver configured to receive a query on the databases from a query issuer; and a query executor configured to execute a plurality of transactions based on information relating to the received query, generate a log for each transaction, and issue log write requests for writing the generated logs in log storage areas, the query executor configured to records sequence numbers of logs in the logs of transactions belonging to a first-class transaction set which is a set of transactions of which results are different depending on a transaction execution order.

2 . The database management system according to claim 1 , further comprising:
sequence number managers configured to manage the sequence number of the log with respect to each of a plurality of database portions which are divided portions of the databases, wherein the sequence number managed by each sequence number manager is updated every time the log of a transaction that has updated the database portion corresponding to the sequence number manager is generated, M logs (M is an integer of 1 or more and N or less) are generated as the logs of a transaction that has updated N database portions (N is an integer of 2 or more) among the plurality of database portions, and at least one of the M logs includes two or more sequence numbers among N sequence numbers respectively corresponding to the N database portions.

3 . The database management system according to claim 2 , wherein
N log storage areas respectively corresponding to the N database portions are provided, a log that includes one sequence number is written to a log storage area corresponding to the sequence number, and a log that includes the two or more sequence numbers is written to anyone of two or more log storage areas respectively corresponding to the two or more sequence numbers.

4 . The database management system according to claim 2 , wherein M=1.

5 . The database management system according to claim 2 , wherein
a plurality of I/O (input/output) resources respectively corresponding to the plurality of database portions are provided, a log that includes one sequence number is written, via an I/O resource corresponding to the sequence number, to a log storage area corresponding to the I/O resource, and a log that includes the two or more sequence numbers is written, via anyone of two or more I/O resources respectively corresponding to the two or more sequence numbers, to a log storage area corresponding to the I/O resource.

6 . The database management system according to claim 1 , wherein the query executor is configured not to record sequence numbers in logs of transactions belonging to a second-class transaction set which is a set of transactions of which results are not influenced by a transaction execution order.

7 . The database management system according to claim 6 , wherein the query executor is configured to determine whether an execution target transaction belongs to the first transaction set or the second-class transaction set based on the information on the query.

8 . The database management system according to claim 7 , further comprising:
a query execution plan generator configured to generate a query execution plan including information indicating one or more database operations necessary for executing the received query and an execution order of the one or more database operations, based on the received query, wherein the information relating to the query is information indicating the query execution plan.

9 . The database management system according to claim 1 , wherein the query executor is configured to generate one or more checkpoint logs including all sequence numbers respectively corresponding to all sequence number managers for each checkpoint.

10 . The database management system according to claim 9 , wherein the number of checkpoint logs in each checkpoint is smaller than the number of database portions.

11 . The database management system according to claim 9 , further comprising:
a recovery executer configured to recover a database at a time point of a designated first checkpoint, wherein the query executor is configured to back up a database at least at one checkpoint among a plurality of checkpoints, and the recovery executer is configured to
load a database corresponding to a second checkpoint which is the same as the first checkpoint or earlier than the first checkpoint, among backed-up databases; and
set sequence numbers in a checkpoint log corresponding to the second checkpoint to the sequence number managers corresponding to the sequence numbers, respectively.

12 . The database management system according to claim 11 , wherein
when the second checkpoint is different from the first checkpoint, the recovery executer is configured to recover, for each database portion of the loaded database, the database portion using one or more logs between the second checkpoint and the first checkpoint, stored in the log storage area corresponding to the database portion, the one or more logs being used in ascending order of the sequence numbers in the logs, in the recovery of each database portion, for a log that includes a corresponding sequence number which is a sequence number corresponding to the database portion and one or more non-corresponding sequence numbers which are one or more sequence numbers other than the corresponding sequence number, the recovery executer is configured to perform update according to the log, for the database portion and one or more database portions respectively corresponding to the one or more non-corresponding sequence numbers, and in the recovery of each database portion, when the sequence number in the log corresponding to the database portion is not a number next to a previously used sequence number in the log, the recovery executer is configured to wait for a log that includes the next number.

13 . The database management system according to claim 2 , wherein the database is present on a main memory.

14 . A computer system for managing databases, comprising:
an interface device coupled to log storage areas; and a processor coupled to the interface device, the processor configured to execute a plurality of transactions, generate a log for each transaction during execution of the plurality of transactions, and store the generated logs in the log storage areas, and the processor configured to records sequence numbers of logs at least in the logs of transactions belonging to a set of transactions of which results are different depending on a transaction execution order.

15 . A database management method for managing databases, comprising:
generating a log for each transaction during execution of a plurality of transactions; storing the generated logs in log storage areas; and recording sequence numbers of logs at least in the generated logs of transactions belonging to a set of transactions of which the results are different depending on a transaction execution order.

Assignees

• Hitachi Ltd

Inventors

• Tomoda Atsushi
• Isoda Yuuya
• Ushijima Kazutomo

Classifications

• G06F17/30185

  Physics · mapped topic

• G06F17/30477

  Physics · mapped topic

• G06F17/30371 Primary

  Physics · mapped topic

• G06F16/2365 Primary

  Ensuring data consistency and integrity · CPC title

• G06F16/2358 Primary

  Change logging, detection, and notification (replication G06F16/27) · CPC title