Version garbage collection using snapshot lists

摘要

Systems, methods and computer program product embodiments for providing version garbage collection using snapshot lists are disclosed herein. Version garbage collection using snapshot lists includes storing, by at least one processor, versions of a record in a database table, the record comprising a record value and a version timestamp, storing, by the at least one processor, active snapshots in two levels of active snapshot lists, an active snapshot comprising a transaction identifier and a snapshot timestamp, determining, by the at least one processor, a minimum active snapshot from the active snapshots in the two levels of active snapshot lists and deleting, by the at least one processor, versions of the record having a version timestamp earlier than a snapshot timestamp of the minimum active snapshot.

主权项

1. A method, comprising:
locating, by at least one processor, a least-recently-active snapshot for a database table from a global active snapshot list and a table-specific active snapshot list, wherein the table-specific active snapshot list comprises a plurality of active snapshots relocated from the global active snapshot list to the table-specific active snapshot list,
wherein the global active snapshot list is associated with a plurality of database tables including the database table,wherein the table-specific active snapshot list is associated with the database table, andwherein an active snapshot, generated by an active transaction, from the plurality of active snapshots was relocated by disassociating the active snapshot with the plurality of database tables and associating the active snapshot with the database table, wherein the relocation is based on an isolation level of the active transaction; and deleting, by the at least one processor, a snapshot version of a record in the database table if the snapshot version has a snapshot version timestamp earlier than a least-recently-active snapshot timestamp associated with the located least-recently-active snapshot.