Fix improper matching of resjunk column names for FOR UPDATE in subselect.

Flattening of subquery range tables during setrefs.c could lead to the
rangetable indexes in PlanRowMark nodes not matching up with the column
names previously assigned to the corresponding resjunk ctid (resp. tableoid
or wholerow) columns.  Typical symptom would be either a "cannot extract
system attribute from virtual tuple" error or an Assert failure.  This
wasn't a problem before 9.0 because we didn't support FOR UPDATE below the
top query level, and so the final flattening could never renumber an RTE
that was relevant to FOR UPDATE.  Fix by using a plan-tree-wide unique
number for each PlanRowMark to label the associated resjunk columns, so
that the number need not change during flattening.

Per report from David Johnston (though I'm darned if I can see how this got
past initial testing of the relevant code).  Back-patch to 9.0.

1 files changed, 10 insertions, 3 deletions

diff --git a/src/backend/executor/execMain.c b/src/backend/executor/execMain.c
index 600f7e03345..7df7f5cdf0d 100644
--- a/src/backend/executor/execMain.c
+++ b/src/backend/executor/execMain.c
@@ -742,6 +742,7 @@ InitPlan(QueryDesc *queryDesc, int eflags)
 		erm->relation = relation;
 		erm->rti = rc->rti;
 		erm->prti = rc->prti;
+		erm->rowmarkId = rc->rowmarkId;
 		erm->markType = rc->markType;
 		erm->noWait = rc->noWait;
 		ItemPointerSetInvalid(&(erm->curCtid));
@@ -1425,23 +1426,29 @@ ExecBuildAuxRowMark(ExecRowMark *erm, List *targetlist)
 		/* if child rel, need tableoid */
 		if (erm->rti != erm->prti)
 		{
-			snprintf(resname, sizeof(resname), "tableoid%u", erm->prti);
+			snprintf(resname, sizeof(resname), "tableoid%u", erm->rowmarkId);
 			aerm->toidAttNo = ExecFindJunkAttributeInTlist(targetlist,
 														   resname);
+			if (!AttributeNumberIsValid(aerm->toidAttNo))
+				elog(ERROR, "could not find junk %s column", resname);
 		}
 
 		/* always need ctid for real relations */
-		snprintf(resname, sizeof(resname), "ctid%u", erm->prti);
+		snprintf(resname, sizeof(resname), "ctid%u", erm->rowmarkId);
 		aerm->ctidAttNo = ExecFindJunkAttributeInTlist(targetlist,
 													   resname);
+		if (!AttributeNumberIsValid(aerm->ctidAttNo))
+			elog(ERROR, "could not find junk %s column", resname);
 	}
 	else
 	{
 		Assert(erm->markType == ROW_MARK_COPY);
 
-		snprintf(resname, sizeof(resname), "wholerow%u", erm->prti);
+		snprintf(resname, sizeof(resname), "wholerow%u", erm->rowmarkId);
 		aerm->wholeAttNo = ExecFindJunkAttributeInTlist(targetlist,
 														resname);
+		if (!AttributeNumberIsValid(aerm->wholeAttNo))
+			elog(ERROR, "could not find junk %s column", resname);
 	}
 
 	return aerm;