Halloween protection in a multi-version database system

摘要

Mitigating problems related to the Halloween problem including where update operations potentially allow the record to be visited more than once during the operation. A method includes accessing an instance of a data store operation statement. The instance of the data store operation statement is executed causing an update or delete to an old version of data store record or creation of a data store record resulting in a new version of the data store record in the case of an update or creation of a data store record and a deleted version of the data store record in the case of a delete in the data store. The instance of the data store operation statement is correlated with the new version of the data store record or the deleted version of the data store record.

主权项

1. In a computing environment, a method of mitigating problems related to the Halloween problem including where update operations allow the record to be visited more than once during the operation, the method comprising:
accessing an instance of a data store operation statement, wherein the data store operation statement is part of a transaction with a plurality of different data store operation statements, and wherein the data store operation statement has a first identifier associated with the data store operation statement that is different than identifiers for the other data store operation statements within the same transaction; executing the instance of the data store operation statement causing an update or delete to an old version of data store record or creation of a data store record resulting in a new version of the data store record in the case of an update or creation of a data store record or a deleted version of the data store record in the case of a delete in the data store; and correlating the instance of the data store operation statement with the new version of the data store record or the deleted version of the data store record by storing the first identifier associated with the instance of the data store operation statement with the new version of the data store record, wherein the correlating the instance of the data store operation statement with the new version of the data store record is used to prevent the instance of the data store operation statement from reading the new version of the data store record so as to prevent the instance of a data store operation statement from seeing its own changes, but does not prevent the other data store operations statements in the same transaction from seeing the changes of the data store operation statement during execution of the transaction.