From: Tom Lane Date: Tue, 24 Mar 2015 19:53:06 +0000 (-0400) Subject: Fix ExecOpenScanRelation to take a lock on a ROW_MARK_COPY relation. X-Git-Tag: REL9_2_11~49 X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=3fbfd5dbeca7931b40d9ec919fb64c3f08893848;p=postgresql 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.) --- diff --git a/src/backend/executor/execMain.c b/src/backend/executor/execMain.c index df6af1b898..2c4b1ab77e 100644 --- a/src/backend/executor/execMain.c +++ b/src/backend/executor/execMain.c @@ -804,6 +804,10 @@ InitPlan(QueryDesc *queryDesc, int eflags) if (rc->isParent) continue; + /* + * 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 e4e70c41b6..65e4904875 100644 --- a/src/backend/executor/execUtils.c +++ b/src/backend/executor/execUtils.c @@ -819,7 +819,9 @@ ExecOpenScanRelation(EState *estate, Index scanrelid) { 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;