On Fri, Apr 3, 2026 at 11:14 PM Tom Lane <[email protected]> wrote: > I believe that we probably will need to do something in this > area before v19 release. If we're willing to commit to it being > "run the tests serially", then sure we can wait awhile before > actually doing that. Maybe we'll even think of a better idea > ... but what we can do about this post-freeze seems pretty > constrained to me.
Here's a new patch set. All of these patches are new, but I'm continuing to increment the same version number sequence. 0001 and 0002 implement the "retry a few times" idea for avoiding test_plan_advice failures. I argue that (a) these are reasonable post-commit stabilization that should not be blocked by feature freeze and (b) most people here will be happier with a solution like this that will normally cost very little than they will be with switching test_plan_advice to executing serially. The RMT can decide whether it agrees. The other question here is whether it's really a good idea to apply this now considering that we've seen only one failure so far. I think it's probably a good idea to do something like this before release, so that we hopefully reduce the false positive rate from the test to something much closer to zero, but I think we've still had only the one failure, and I'm really interested in knowing how close the failure rate is to zero already. The RMT may have an opinion on how long to wait before doing something like this, too. 0003 fixes the problem with tablesample scans that Alexander Lakhin reported. The bug occurs when a tablesample handler does not set repeatable_across_scans and the resulting Sample Scan appears below a join. The test case provided by Alexander shows the Sample Scan on the inner side of the join, but it's also possible to construct a case where it occurs on the outer side of the join. This commit adds tests for both cases. 0004 fixes an oversight in commit 6455e55b0da47255f332a96f005ba0dd1c7176c2, which failed to add a new pg_regress test to the pg_plan_advice Makefile. 0005 fixes the other issue that Alexander Lakhin recently reported, which manifested as ERROR: no rtoffset for plan unnamed_subquery when trying to generate advice. That turns out to occur when a subquery is proven empty and that subquery contains a semijoin that could have been implemented by making one side unique. I chose a different fix than what I mentioned in my response to Alexander's email. There was already code that handles the case where a SubPlanRTInfo exists and is marked dummy, and this fix extends that handling to the case where no SubPlanRTInfo exists at all, which seems better than treating those two cases in separate parts of the code. I don't think that anyone will argue that 0003-0005 are things we can't or shouldn't fix after feature freeze, and I plan to apply those fixes shortly after feature freeze, unless there are objections or better ideas. I could rush them in before that, too, but I don't think what the tree needs are more people trying to commit all at once right now. Thanks, -- Robert Haas EDB: http://www.enterprisedb.com
v26-0001-pg_plan_advice-Export-feedback-related-definitio.patch
Description: Binary data
v26-0005-pg_plan_advice-Fix-a-bug-when-a-subquery-is-prun.patch
Description: Binary data
v26-0002-test_plan_advice-Guard-against-advice-instabilit.patch
Description: Binary data
v26-0003-pg_plan_advice-Handle-non-repeatable-TABLESAMPLE.patch
Description: Binary data
v26-0004-pg_plan_advice-Add-alternatives-test-to-Makefile.patch
Description: Binary data
