| 摘要 |
In a database system, derived data (often called view data or view tables) depends on other data, often called base data (or base tables). When base data on which derived data depends is updated, including changes, additions, and/or deletions, those updates need to be propagated to derived data. Some types of updates, if repeated, result in an incorrect view data state; these updates are termed non-idempotent. To avoid repeating non-idempotent view data updates, signatures are computed that are repeatable, but yet unique to base data on which the view data is based, the view data being updated, and sequence information for updates to the base data (where applicable) and sequence data for multiple changes to the view being updated. The signatures allow detection of view updates that were committed prior to a failure, but which were not confirmed as having been committed to a process that computes the view updates. |
