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 update errors including where update operations potentially allow a record to be visited more than once during an operation, the method comprising:
accessing an instance of a data store operation statement; executing the instance of the data store operation statement causing an update or delete to an old version of a 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 a 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, wherein correlating the instance of the data store operation statement with the new version of the data store record prevents 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 accessing its own changes while not preventing the instance of the data store operation statement from accessing a state of the data store as it existed before the data store operation statement started executing, wherein the state of the data store as it existed before the data store operation statement started executing comprises at least one or more of a record created or a record deleted by a previous data store operation statement.