From feeb526cfe33657b8aa8b0cdd45b2ef0d9898877 Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Tue, 24 Mar 2015 15:53:06 -0400
Subject: [PATCH] Fix ExecOpenScanRelation to take a lock on a ROW_MARK_COPY
relation.
ExecOpenScanRelation assumed that any relation listed in the ExecRowMark
list has been locked by InitPlan; but this is not true if the rel's
markType is ROW_MARK_COPY, which is possible if it's a foreign table.
In most (possibly all) cases, failure to acquire a lock here isn't really
problematic because the parser, planner, or plancache would have taken the
appropriate lock already. In principle though it might leave us vulnerable
to working with a relation that we hold no lock on, and in any case if the
executor isn't depending on previously-taken locks otherwise then it should
not do so for ROW_MARK_COPY relations.
Noted by Etsuro Fujita. Back-patch to all active versions, since the
inconsistency has been there a long time. (It's almost certainly
irrelevant in 9.0, since that predates foreign tables, but the code's
still wrong on its own terms.)
---
src/backend/executor/execMain.c | 4 ++++
src/backend/executor/execUtils.c | 4 +++-
2 files changed, 7 insertions(+), 1 deletion(-)
diff --git a/src/backend/executor/execMain.c b/src/backend/executor/execMain.c
index ad7e2072908..90d37b566ae 100644
--- a/src/backend/executor/execMain.c
+++ b/src/backend/executor/execMain.c
@@ -817,6 +817,10 @@ InitPlan(QueryDesc *queryDesc, int eflags)
/* get relation's OID (will produce InvalidOid if subquery) */
relid = getrelid(rc->rti, rangeTable);
+ /*
+ * If you change the conditions under which rel locks are acquired
+ * here, be sure to adjust ExecOpenScanRelation to match.
+ */
switch (rc->markType)
{
case ROW_MARK_EXCLUSIVE:
diff --git a/src/backend/executor/execUtils.c b/src/backend/executor/execUtils.c
index 022041bea44..0736d2a3102 100644
--- a/src/backend/executor/execUtils.c
+++ b/src/backend/executor/execUtils.c
@@ -820,7 +820,9 @@ ExecOpenScanRelation(EState *estate, Index scanrelid, int eflags)
{
ExecRowMark *erm = lfirst(l);
- if (erm->rti == scanrelid)
+ /* Keep this check in sync with InitPlan! */
+ if (erm->rti == scanrelid &&
+ erm->relation != NULL)
{
lockmode = NoLock;
break;
--
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