From f6661d3df228dbbf50efb04f2b760774a6f2bfff Mon Sep 17 00:00:00 2001 From: Andres Freund Date: Sun, 16 Aug 2020 14:21:37 -0700 Subject: [PATCH] Fix use of wrong index in ComputeXidHorizons(). This bug, recently introduced in 941697c3c1a, at least lead to vacuum failing because it found tuples inserted by a running transaction, but below the freeze limit. The freeze limit in turn is directly affected by the aforementioned bug. Thanks to Tom Lane figuring how to make the bug reproducible. We should add a few more assertions to make sure this type of bug isn't as hard to notice, but it's not yet clear how to best do so. Co-Diagnosed-By: Tom Lane Author: Andres Freund Discussion: https://postgr.es/m/1013484.1597609043@sss.pgh.pa.us --- src/backend/storage/ipc/procarray.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index 8262abd42e6..96e4a878576 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -1663,7 +1663,7 @@ ComputeXidHorizons(ComputeXidHorizonsResult *h) TransactionId xmin; /* Fetch xid just once - see GetNewTransactionId */ - xid = UINT32_ACCESS_ONCE(other_xids[pgprocno]); + xid = UINT32_ACCESS_ONCE(other_xids[index]); xmin = UINT32_ACCESS_ONCE(proc->xmin); /*