gfphoenix78 opened a new pull request, #1890: URL: https://github.com/apache/cloudberry/pull/1890
GetSnapshotData() on a QE computes xmin under ProcArrayLock but reads/advances DistributedLogShared->oldestXmin afterwards, in a different lock domain. In that window a concurrent backend can advance the shared oldestXmin past this snapshot's xmin: when the transaction whose local xid equals xmin aborts, its distributed-log entry keeps distribXid == 0, so DistributedLog_AdvanceOldestXmin()'s forward scan skips over it instead of stopping, bumping oldestXmin beyond xmin. The resulting globalxmin > xmin then tripped a hard elog(ERROR) and failed the query (seen intermittently in the partition_prune regression test). The aborted xid is invisible to this snapshot anyway, and the visibility horizon only needs to be a valid lower bound, so a horizon at our own xmin loses nothing. Clamp globalxmin to xmin instead of erroring -- always safe, and consistent with the clamp already done in DistributedLog_GetOldestXmin(). <!-- Thank you for your contribution to Apache Cloudberry (Incubating)! --> Fixes #ISSUE_Number ### What does this PR do? <!-- Brief overview of the changes, including any major features or fixes --> ### Type of Change - [ ] Bug fix (non-breaking change) - [ ] New feature (non-breaking change) - [ ] Breaking change (fix or feature with breaking changes) - [ ] Documentation update ### Breaking Changes <!-- Remove if not applicable. If yes, explain impact and migration path --> ### Test Plan <!-- How did you test these changes? --> - [ ] Unit tests added/updated - [ ] Integration tests added/updated - [ ] Passed `make installcheck` - [ ] Passed `make -C src/test installcheck-cbdb-parallel` ### Impact <!-- Remove sections that don't apply --> **Performance:** <!-- Any performance implications? --> **User-facing changes:** <!-- Any changes visible to users? --> **Dependencies:** <!-- New dependencies or version changes? --> ### Checklist - [ ] Followed [contribution guide](https://cloudberry.apache.org/contribute/code) - [ ] Added/updated documentation - [ ] Reviewed code for security implications - [ ] This PR contains AI-assisted code generation - [ ] Requested review from [cloudberry committers](https://github.com/orgs/apache/teams/cloudberry-committers) ### Additional Context <!-- Any other information that would help reviewers? Remove if none --> ### CI Skip Instructions <!-- To skip CI builds, add the appropriate CI skip identifier to your PR title. The identifier must: - Be in square brackets [] - Include the word "ci" and either "skip" or "no" - Only use for documentation-only changes or when absolutely necessary --> --- <!-- Join our community: - Mailing list: [[email protected]](https://lists.apache.org/[email protected]) (subscribe: [email protected]) - Discussions: https://github.com/apache/cloudberry/discussions --> -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected] --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
