US 10,761,946 B2Granted

Transaction commit protocol with recoverable commit identifier

AssigneeSap SE

InventorsChristian Bensberg, Steffen Geissinger, Juchang Lee, Chang Gyoo Park, Kyu Hwan Kim, Deok Koo Kim

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Abstract

Technologies are described for facilitating database system recovery in a distributed database environment having a master node and at least one slave node. The master node maintains an in-memory reference that includes transaction identifiers and their corresponding commit identifiers. When a slave node requests that a commit identifier be assigned to a transaction, the transaction and commit identifiers for the transaction are added to the in-memory reference. The commit identifier is sent by the master node to the slave node. The slave node writes a log entry to a commit log that includes the transaction identifier and the assigned commit identifier. If the database system is interrupted before the slave node writes the commit log entry, the slave node can request the commit identifier for the transaction from the master node, which retrieves the identifier from the in-memory reference.

Claims23

Dependent claims

One or more computer-readable storage media storing computer-executable instructions for causing a computing system to perform processing to facilitate database recovery at a slave database system node, the slave node in communication with a master database system node, the processing at the master node comprising:

receiving a transaction identifier from the slave node, the transaction identifier associated with a database transaction executed at least in part at the slave node and useable to identify the database transaction from among a plurality of transactions executed in a database system comprising the master node and the slave node;
assigning a commit identifier to the transaction, the commit identifier representing a state of the database system and useable to order at least a portion of the plurality of transactions;
storing in memory the transaction identifier and the commit identifier in a manner indicating that the commit identifier was assigned to the transaction having the transaction identifier, the storing providing an in-memory reference, wherein the transaction identifier and the commit identifier are stored in an in-memory structure storing as elements a plurality of associations between transaction identifiers and their assigned commit identifiers;
writing a commit log entry indicating the assignment of the commit identifier to the transaction, the commit log being different than the in-memory structure;
sending a commit communication to the slave node, wherein the in-memory reference is persisted in memory for at least a first period of time after the writing a commit log entry and after the sending a commit communication;
receiving a communication from the slave node comprising the transaction identifier, the communication from the slave node indicating that the master node can remove the transaction identifier and its associated commit identifier from the in-memory structure;
and
removing the transaction identifier and its associated commit identifier from the in-memory structure in response to the communication from the slave node.

5 more elements

A method, implemented at least in part by a slave node comprising a processing unit and memory, the slave node being in communication with a master node, for facilitating database system recovery within a database environment, the method comprising:

receiving a database transaction comprising one or more requests for a database operation;
writing a precommit log entry for the transaction;
sending a request to the master node to assign a commit identifier to the transaction, the request including an identifier for the transaction, the commit identifier representing a state of a database system comprising the master node and the slave node and useable to order at least a portion of the plurality of transactions, wherein the sending the request to the master node is not in response to a commit processing request received from the master node;
receiving the commit identifier from the master node;
after receiving the commit identifier from the master node, writing a commit log entry comprising the transaction identifier and the commit identifier, the commit log entry indicating that the commit identifier was assigned to the transaction having the transaction identifier;
and
sending a communication to the master node, the communication comprising the transaction identifier, wherein the communication indicates to the master node that the master node may remove the transaction identifier and the commit identifier from an in-memory structure maintained by the master node.

4 more elements

A server comprising a processing unit and memory, wherein the server is configured to operate a slave node of a distributed database system, the slave node being in communication with a master node, and further configured to perform a method for facilitating database system recovery, the method comprising:

receiving a database transaction comprising one or more requests for a database operation;
sending a request to the master node to assign a commit identifier to the transaction, the request including an identifier for the transaction, wherein the sending the request to the master node is not in response to a commit processing request received from the master node;
writing a log entry associated with the transaction and including the transaction identifier;
receiving the commit identifier from the master node;
after receiving the commit identifier from the master node, writing a commit log entry comprising the transaction identifier and the commit identifier;
and
sending a communication to the master node, the communication comprising the transaction identifier, wherein the communication indicates to the master node that the master node may remove the transaction identifier and the commit identifier from an in-memory structure maintained by the master node.

4 more elements

Dependencies are inferred from the claim text.

Facts

Application: 15/430,091Filed 10 Feb 2017
Published: US 2018/0232412 A116 Aug 2018
Granted: 1 Sep 2020
Term ends: Not estimatedThe source records don’t support an estimate.

Classification6 codes

G06F 11/1464
Management of the backup or restore process: for networked environments
G06F 11/1474
Error detection or correction of the data by redundancy in operations: in transactions
G06F 11/1441
At system level: resetting or repowering
G06F 2201/80
Indexing scheme relating to error detection, to error correction, and to monitoring: database-specific techniques