Prevent data from re-appearing on startup in some cases #14232
Merged
Conversation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
Closes #14229
This PR fixes a strange bug where data can re-appear after a restart. The issue arises if the cache is snapshotted before a write lands in the WAL. In such a scenario, the Engine thinks that the WAL is empty, and decides it does not need truncating when the cache snapshot completes.
The data in the WAL then persists after the snapshot, and is then replayed again on startup. The catch is that if a user attempts to delete this data post-snapshot, no delete entry will be added to the WAL because the cache is empty. So when the replay happens there is no delete command to replay.