From 47a338cfcd67139a1f91892b080934fcfc3aea03 Mon Sep 17 00:00:00 2001 From: Thomas Munro Date: Thu, 9 May 2019 19:11:46 +1200 Subject: [PATCH] Fix SxactGlobalXmin tracking. Commit bb16aba50 broke the code that maintains SxactGlobalXmin. It could get stuck when a well-timed READ ONLY transaction runs. If SxactGlobalXmin stops advancing, transactions on the FinishedSerializableTransactions queue are never cleaned up, so resources are effectively leaked. Revert that hunk of the commit. Also revert another similar hunk that was probably harmless, but unnecessary and unjustified, relating to the DOOMED flag in case of RO_SAFE early release. Author: Thomas Munro Reported-by: Tom Lane Discussion: https://postgr.es/m/16170.1557251214%40sss.pgh.pa.us --- src/backend/storage/lmgr/predicate.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-) diff --git a/src/backend/storage/lmgr/predicate.c b/src/backend/storage/lmgr/predicate.c index 4e4d04bae3..7f607b2bf8 100644 --- a/src/backend/storage/lmgr/predicate.c +++ b/src/backend/storage/lmgr/predicate.c @@ -3438,8 +3438,7 @@ ReleasePredicateLocks(bool isCommit, bool isReadOnlySafe) * cleanup. This means it should not be considered when calculating * SxactGlobalXmin. */ - if (!isReadOnlySafe) - MySerializableXact->flags |= SXACT_FLAG_DOOMED; + MySerializableXact->flags |= SXACT_FLAG_DOOMED; MySerializableXact->flags |= SXACT_FLAG_ROLLED_BACK; /* @@ -3635,8 +3634,7 @@ ReleasePredicateLocks(bool isCommit, bool isReadOnlySafe) * was launched. */ needToClear = false; - if (!isReadOnlySafe && - TransactionIdEquals(MySerializableXact->xmin, PredXact->SxactGlobalXmin)) + if (TransactionIdEquals(MySerializableXact->xmin, PredXact->SxactGlobalXmin)) { Assert(PredXact->SxactGlobalXminCount > 0); if (--(PredXact->SxactGlobalXminCount) == 0) -- 2.30.2