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.

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;

src/backend/nodes/copyfuncs.c

@@ -906,6 +906,7 @@ _copyPlanRowMark(PlanRowMark *from)
 
 	COPY_SCALAR_FIELD(rti);
 	COPY_SCALAR_FIELD(prti);
+	COPY_SCALAR_FIELD(rowmarkId);
 	COPY_SCALAR_FIELD(markType);
 	COPY_SCALAR_FIELD(noWait);
 	COPY_SCALAR_FIELD(isParent);

src/backend/nodes/outfuncs.c

@@ -808,6 +808,7 @@ _outPlanRowMark(StringInfo str, PlanRowMark *node)
 
 	WRITE_UINT_FIELD(rti);
 	WRITE_UINT_FIELD(prti);
+	WRITE_UINT_FIELD(rowmarkId);
 	WRITE_ENUM_FIELD(markType, RowMarkType);
 	WRITE_BOOL_FIELD(noWait);
 	WRITE_BOOL_FIELD(isParent);
@@ -1609,6 +1610,7 @@ _outPlannerGlobal(StringInfo str, PlannerGlobal *node)
 	WRITE_NODE_FIELD(relationOids);
 	WRITE_NODE_FIELD(invalItems);
 	WRITE_UINT_FIELD(lastPHId);
+	WRITE_UINT_FIELD(lastRowMarkId);
 	WRITE_BOOL_FIELD(transientPlan);
 }
 

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;

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;
 

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),

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;

src/include/nodes/execnodes.h

@@ -417,6 +417,7 @@ typedef struct ExecRowMark
 	Relation	relation;		/* opened and suitably locked relation */
 	Index		rti;			/* its range table index */
 	Index		prti;			/* parent range table index, if child */
+	Index		rowmarkId;		/* unique identifier for resjunk columns */
 	RowMarkType markType;		/* see enum in nodes/plannodes.h */
 	bool		noWait;			/* NOWAIT option */
 	ItemPointerData curCtid;	/* ctid of currently locked tuple, if any */

src/include/nodes/plannodes.h

@@ -749,7 +749,11 @@ typedef enum RowMarkType
  * The tableoid column is only present for an inheritance hierarchy.
  * When markType == ROW_MARK_COPY, there is instead a single column named
  *		wholerow%u			whole-row value of relation
- * In all three cases, %u represents the parent rangetable index (prti).
+ * In all three cases, %u represents the rowmark ID number (rowmarkId).
+ * This number is unique within a plan tree, except that child relation
+ * entries copy their parent's rowmarkId.  (Assigning unique numbers
+ * means we needn't renumber rowmarkIds when flattening subqueries, which
+ * would require finding and renaming the resjunk columns as well.)
  * Note this means that all tables in an inheritance hierarchy share the
  * same resjunk column names.  However, in an inherited UPDATE/DELETE the
  * columns could have different physical column numbers in each subplan.
@@ -759,6 +763,7 @@ typedef struct PlanRowMark
 	NodeTag		type;
 	Index		rti;			/* range table index of markable relation */
 	Index		prti;			/* range table index of parent relation */
+	Index		rowmarkId;		/* unique identifier for resjunk columns */
 	RowMarkType markType;		/* see enum above */
 	bool		noWait;			/* NOWAIT option */
 	bool		isParent;		/* true if this is a "dummy" parent entry */

src/include/nodes/relation.h

@@ -82,6 +82,8 @@ typedef struct PlannerGlobal
 
 	Index		lastPHId;		/* highest PlaceHolderVar ID assigned */
 
+	Index		lastRowMarkId;	/* highest PlanRowMark ID assigned */
+
 	bool		transientPlan;	/* redo plan when TransactionXmin changes? */
 } PlannerGlobal;