From 5ab0ad5c7e70dd44d87dcdad58d9064fe10aa3e3 Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Fri, 11 Jan 2002 20:07:03 +0000
Subject: [PATCH] VACUUM must make sure that a HEAP_MARKED_FOR_UPDATE tuple
gets marked as either HEAP_XMAX_COMMITTED or HEAP_XMAX_INVALID once the
updating transaction is gone. Otherwise some other transaction may come
along and try to test the commit status of t_xmax later --- which could be
after VACUUM has recycled the CLOG status for that xact. Bug introduced in
post-beta4 bug fix.
---
src/backend/utils/time/tqual.c | 18 ++++++++++++++++--
1 file changed, 16 insertions(+), 2 deletions(-)
diff --git a/src/backend/utils/time/tqual.c b/src/backend/utils/time/tqual.c
index 6c7f579312e..b71b97088bf 100644
--- a/src/backend/utils/time/tqual.c
+++ b/src/backend/utils/time/tqual.c
@@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
- * $Header: /cvsroot/pgsql/src/backend/utils/time/tqual.c,v 1.45 2001/12/19 17:18:39 tgl Exp $
+ * $Header: /cvsroot/pgsql/src/backend/utils/time/tqual.c,v 1.46 2002/01/11 20:07:03 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -742,7 +742,21 @@ HeapTupleSatisfiesVacuum(HeapTupleHeader tuple, TransactionId OldestXmin)
if (tuple->t_infomask & HEAP_MARKED_FOR_UPDATE)
{
- /* "deleting" xact really only marked it for update */
+ /*
+ * "Deleting" xact really only marked it for update, so the tuple
+ * is live in any case. However, we must make sure that either
+ * XMAX_COMMITTED or XMAX_INVALID gets set once the xact is gone;
+ * otherwise it is unsafe to recycle CLOG status after vacuuming.
+ */
+ if (!(tuple->t_infomask & HEAP_XMAX_COMMITTED))
+ {
+ if (TransactionIdIsInProgress(tuple->t_xmax))
+ return HEAPTUPLE_LIVE;
+ if (TransactionIdDidCommit(tuple->t_xmax))
+ tuple->t_infomask |= HEAP_XMAX_COMMITTED;
+ else /* it's either aborted or crashed */
+ tuple->t_infomask |= HEAP_XMAX_INVALID;
+ }
return HEAPTUPLE_LIVE;
}
--
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