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.

4 files changed, 8 insertions, 4 deletions

diff --git a/src/backend/optimizer/plan/planner.c b/src/backend/optimizer/plan/planner.c
index b52eebe2aa..01b90383cf 100644
--- a/src/backend/optimizer/plan/planner.c
+++ b/src/backend/optimizer/plan/planner.c
@@ -166,6 +166,7 @@ standard_planner(Query *parse, int cursorOptions, ParamListInfo boundParams)
 	glob->relationOids = NIL;
 	glob->invalItems = NIL;
 	glob->lastPHId = 0;
+	glob->lastRowMarkId = 0;
 	glob->transientPlan = false;
 
 	/* Determine what fraction of the plan is likely to be scanned */
@@ -1885,6 +1886,7 @@ preprocess_rowmarks(PlannerInfo *root)
 
 		newrc = makeNode(PlanRowMark);
 		newrc->rti = newrc->prti = rc->rti;
+		newrc->rowmarkId = ++(root->glob->lastRowMarkId);
 		if (rc->forUpdate)
 			newrc->markType = ROW_MARK_EXCLUSIVE;
 		else
@@ -1910,6 +1912,7 @@ preprocess_rowmarks(PlannerInfo *root)
 
 		newrc = makeNode(PlanRowMark);
 		newrc->rti = newrc->prti = i;
+		newrc->rowmarkId = ++(root->glob->lastRowMarkId);
 		/* real tables support REFERENCE, anything else needs COPY */
 		if (rte->rtekind == RTE_RELATION)
 			newrc->markType = ROW_MARK_REFERENCE;
diff --git a/src/backend/optimizer/plan/setrefs.c b/src/backend/optimizer/plan/setrefs.c
index 867238ecc8..d004f6cf12 100644
--- a/src/backend/optimizer/plan/setrefs.c
+++ b/src/backend/optimizer/plan/setrefs.c
@@ -252,7 +252,7 @@ set_plan_references(PlannerGlobal *glob, Plan *plan,
 		newrc = (PlanRowMark *) palloc(sizeof(PlanRowMark));
 		memcpy(newrc, rc, sizeof(PlanRowMark));
 
-		/* adjust indexes */
+		/* adjust indexes ... but *not* the rowmarkId */
 		newrc->rti += rtoffset;
 		newrc->prti += rtoffset;
 
diff --git a/src/backend/optimizer/prep/preptlist.c b/src/backend/optimizer/prep/preptlist.c
index 34b38eb329..63447aa536 100644
--- a/src/backend/optimizer/prep/preptlist.c
+++ b/src/backend/optimizer/prep/preptlist.c
@@ -102,7 +102,7 @@ preprocess_targetlist(PlannerInfo *root, List *tlist)
 						  -1,
 						  InvalidOid,
 						  0);
-			snprintf(resname, sizeof(resname), "ctid%u", rc->rti);
+			snprintf(resname, sizeof(resname), "ctid%u", rc->rowmarkId);
 			tle = makeTargetEntry((Expr *) var,
 								  list_length(tlist) + 1,
 								  pstrdup(resname),
@@ -118,7 +118,7 @@ preprocess_targetlist(PlannerInfo *root, List *tlist)
 							  -1,
 							  InvalidOid,
 							  0);
-				snprintf(resname, sizeof(resname), "tableoid%u", rc->rti);
+				snprintf(resname, sizeof(resname), "tableoid%u", rc->rowmarkId);
 				tle = makeTargetEntry((Expr *) var,
 									  list_length(tlist) + 1,
 									  pstrdup(resname),
@@ -132,7 +132,7 @@ preprocess_targetlist(PlannerInfo *root, List *tlist)
 			var = makeWholeRowVar(rt_fetch(rc->rti, range_table),
 								  rc->rti,
 								  0);
-			snprintf(resname, sizeof(resname), "wholerow%u", rc->rti);
+			snprintf(resname, sizeof(resname), "wholerow%u", rc->rowmarkId);
 			tle = makeTargetEntry((Expr *) var,
 								  list_length(tlist) + 1,
 								  pstrdup(resname),
diff --git a/src/backend/optimizer/prep/prepunion.c b/src/backend/optimizer/prep/prepunion.c
index f62af6c37d..606e5fe60a 100644
--- a/src/backend/optimizer/prep/prepunion.c
+++ b/src/backend/optimizer/prep/prepunion.c
@@ -1294,6 +1294,7 @@ expand_inherited_rtentry(PlannerInfo *root, RangeTblEntry *rte, Index rti)
 
 			newrc->rti = childRTindex;
 			newrc->prti = rti;
+			newrc->rowmarkId = oldrc->rowmarkId;
 			newrc->markType = oldrc->markType;
 			newrc->noWait = oldrc->noWait;
 			newrc->isParent = false;