postgres.git / summary / log / commit / refs

commit    3fbfd5dbeca7931b40d9ec919fb64c3f08893848
Author:   Tom Lane <tgl@sss.pgh.pa.us>
Date:     Tue Mar 24 19:53:06 2015 +0000
First released in: 9.5.0, 9.0.20, 9.1.16, 9.2.11, 9.3.7, 9.4.2

    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 df6af1b898c..2c4b1ab77e3 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 e4e70c41b63..65e4904875a 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;


[parent: 8582ae7aabbe]