Fix problems with cached tuple descriptors disappearing while still in use

by creating a reference-count mechanism, similar to what we did a long time
ago for catcache entries.  The back branches have an ugly solution involving
lots of extra copies, but this way is more efficient.  Reference counting is
only applied to tupdescs that are actually in caches --- there seems no need
to use it for tupdescs that are generated in the executor, since they'll go
away during plan shutdown by virtue of being in the per-query memory context.
Neil Conway and Tom Lane

src/backend/access/common/tupdesc.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/access/common/tupdesc.c,v 1.116 2006/03/16 00:31:54 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/access/common/tupdesc.c,v 1.117 2006/06/16 18:42:21 tgl Exp $
  *
  * NOTES
  *	  some of the executor utility code such as "ExecTypeFromTL" should be
@@ -23,6 +23,7 @@
 #include "catalog/pg_type.h"
 #include "parser/parse_type.h"
 #include "utils/builtins.h"
+#include "utils/resowner.h"
 #include "utils/syscache.h"
 
 
@@ -84,6 +85,7 @@ CreateTemplateTupleDesc(int natts, bool hasoid)
 	desc->tdtypeid = RECORDOID;
 	desc->tdtypmod = -1;
 	desc->tdhasoid = hasoid;
+	desc->tdrefcount = -1;		/* assume not reference-counted */
 
 	return desc;
 }
@@ -116,6 +118,7 @@ CreateTupleDesc(int natts, bool hasoid, Form_pg_attribute *attrs)
 	desc->tdtypeid = RECORDOID;
 	desc->tdtypmod = -1;
 	desc->tdhasoid = hasoid;
+	desc->tdrefcount = -1;		/* assume not reference-counted */
 
 	return desc;
 }
@@ -214,6 +217,12 @@ FreeTupleDesc(TupleDesc tupdesc)
 {
 	int			i;
 
+	/*
+	 * Possibly this should assert tdrefcount == 0, to disallow explicit
+	 * freeing of un-refcounted tupdescs?
+	 */
+	Assert(tupdesc->tdrefcount <= 0);
+
 	if (tupdesc->constr)
 	{
 		if (tupdesc->constr->num_defval > 0)
@@ -246,12 +255,48 @@ FreeTupleDesc(TupleDesc tupdesc)
 	pfree(tupdesc);
 }
 
+/*
+ * Increment the reference count of a tupdesc, and log the reference in
+ * CurrentResourceOwner.
+ *
+ * Do not apply this to tupdescs that are not being refcounted.  (Use the
+ * macro PinTupleDesc for tupdescs of uncertain status.)
+ */
+void
+IncrTupleDescRefCount(TupleDesc tupdesc)
+{
+	Assert(tupdesc->tdrefcount >= 0);
+
+	ResourceOwnerEnlargeTupleDescs(CurrentResourceOwner);
+	tupdesc->tdrefcount++;
+	ResourceOwnerRememberTupleDesc(CurrentResourceOwner, tupdesc);
+}
+
+/*
+ * Decrement the reference count of a tupdesc, remove the corresponding
+ * reference from CurrentResourceOwner, and free the tupdesc if no more
+ * references remain.
+ *
+ * Do not apply this to tupdescs that are not being refcounted.  (Use the
+ * macro ReleaseTupleDesc for tupdescs of uncertain status.)
+ */
+void
+DecrTupleDescRefCount(TupleDesc tupdesc)
+{
+	Assert(tupdesc->tdrefcount > 0);
+
+	ResourceOwnerForgetTupleDesc(CurrentResourceOwner, tupdesc);
+	if (--tupdesc->tdrefcount == 0)
+		FreeTupleDesc(tupdesc);
+}
+
 /*
  * Compare two TupleDesc structures for logical equality
  *
  * Note: we deliberately do not check the attrelid and tdtypmod fields.
  * This allows typcache.c to use this routine to see if a cached record type
  * matches a requested type, and is harmless for relcache.c's uses.
+ * We don't compare tdrefcount, either.
  */
 bool
 equalTupleDescs(TupleDesc tupdesc1, TupleDesc tupdesc2)

src/backend/access/heap/tuptoaster.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/access/heap/tuptoaster.c,v 1.59 2006/03/05 15:58:21 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/access/heap/tuptoaster.c,v 1.60 2006/06/16 18:42:21 tgl Exp $
  *
  *
  * INTERFACE ROUTINES
@@ -892,7 +892,10 @@ toast_flatten_tuple_attribute(Datum value,
 	 * If nothing to untoast, just return the original tuple.
 	 */
 	if (!need_change)
+	{
+		ReleaseTupleDesc(tupleDesc);
 		return value;
+	}
 
 	/*
 	 * Calculate the new size of the tuple.  Header size should not change,
@@ -929,6 +932,7 @@ toast_flatten_tuple_attribute(Datum value,
 	for (i = 0; i < numAttrs; i++)
 		if (toast_free[i])
 			pfree(DatumGetPointer(toast_values[i]));
+	ReleaseTupleDesc(tupleDesc);
 
 	return PointerGetDatum(new_data);
 }

src/backend/commands/tablecmds.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/commands/tablecmds.c,v 1.184 2006/05/10 23:18:39 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/commands/tablecmds.c,v 1.185 2006/06/16 18:42:21 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -2637,6 +2637,9 @@ ATRewriteTable(AlteredTableInfo *tab, Oid OIDNewHeap)
 
 		MemoryContextSwitchTo(oldCxt);
 		heap_endscan(scan);
+
+		ExecDropSingleTupleTableSlot(oldslot);
+		ExecDropSingleTupleTableSlot(newslot);
 	}
 
 	FreeExecutorState(estate);

src/backend/executor/execJunk.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/executor/execJunk.c,v 1.52 2006/03/05 15:58:25 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/executor/execJunk.c,v 1.53 2006/06/16 18:42:21 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -79,7 +79,7 @@ ExecInitJunkFilter(List *targetList, bool hasoid, TupleTableSlot *slot)
 	 * Use the given slot, or make a new slot if we weren't given one.
 	 */
 	if (slot)
-		ExecSetSlotDescriptor(slot, cleanTupType, false);
+		ExecSetSlotDescriptor(slot, cleanTupType);
 	else
 		slot = MakeSingleTupleTableSlot(cleanTupType);
 
@@ -150,7 +150,7 @@ ExecInitJunkFilterConversion(List *targetList,
 	 * Use the given slot, or make a new slot if we weren't given one.
 	 */
 	if (slot)
-		ExecSetSlotDescriptor(slot, cleanTupType, false);
+		ExecSetSlotDescriptor(slot, cleanTupType);
 	else
 		slot = MakeSingleTupleTableSlot(cleanTupType);
 

src/backend/executor/execMain.c

@@ -26,7 +26,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/executor/execMain.c,v 1.270 2006/04/30 18:30:38 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/executor/execMain.c,v 1.271 2006/06/16 18:42:21 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -1445,9 +1445,7 @@ ExecInsert(TupleTableSlot *slot,
 			TupleTableSlot *newslot = estate->es_trig_tuple_slot;
 
 			if (newslot->tts_tupleDescriptor != slot->tts_tupleDescriptor)
-				ExecSetSlotDescriptor(newslot,
-									  slot->tts_tupleDescriptor,
-									  false);
+				ExecSetSlotDescriptor(newslot, slot->tts_tupleDescriptor);
 			ExecStoreTuple(newtuple, newslot, InvalidBuffer, false);
 			slot = newslot;
 			tuple = newtuple;
@@ -1654,9 +1652,7 @@ ExecUpdate(TupleTableSlot *slot,
 			TupleTableSlot *newslot = estate->es_trig_tuple_slot;
 
 			if (newslot->tts_tupleDescriptor != slot->tts_tupleDescriptor)
-				ExecSetSlotDescriptor(newslot,
-									  slot->tts_tupleDescriptor,
-									  false);
+				ExecSetSlotDescriptor(newslot, slot->tts_tupleDescriptor);
 			ExecStoreTuple(newtuple, newslot, InvalidBuffer, false);
 			slot = newslot;
 			tuple = newtuple;

src/backend/executor/execTuples.c

@@ -15,7 +15,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/executor/execTuples.c,v 1.93 2006/04/04 19:35:34 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/executor/execTuples.c,v 1.94 2006/06/16 18:42:22 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -143,7 +143,6 @@ ExecCreateTupleTable(int tableSize)
 		slot->type = T_TupleTableSlot;
 		slot->tts_isempty = true;
 		slot->tts_shouldFree = false;
-		slot->tts_shouldFreeDesc = false;
 		slot->tts_tuple = NULL;
 		slot->tts_tupleDescriptor = NULL;
 		slot->tts_mcxt = CurrentMemoryContext;
@@ -189,8 +188,8 @@ ExecDropTupleTable(TupleTable table,	/* tuple table */
 			TupleTableSlot *slot = &(table->array[i]);
 
 			ExecClearTuple(slot);
-			if (slot->tts_shouldFreeDesc)
-				FreeTupleDesc(slot->tts_tupleDescriptor);
+			if (slot->tts_tupleDescriptor)
+				ReleaseTupleDesc(slot->tts_tupleDescriptor);
 			if (slot->tts_values)
 				pfree(slot->tts_values);
 			if (slot->tts_isnull)
@@ -210,7 +209,7 @@ ExecDropTupleTable(TupleTable table,	/* tuple table */
  *		This is a convenience routine for operations that need a
  *		standalone TupleTableSlot not gotten from the main executor
  *		tuple table.  It makes a single slot and initializes it as
- *		though by ExecSetSlotDescriptor(slot, tupdesc, false).
+ *		though by ExecSetSlotDescriptor(slot, tupdesc).
  * --------------------------------
  */
 TupleTableSlot *
@@ -221,7 +220,6 @@ MakeSingleTupleTableSlot(TupleDesc tupdesc)
 	/* This should match ExecCreateTupleTable() */
 	slot->tts_isempty = true;
 	slot->tts_shouldFree = false;
-	slot->tts_shouldFreeDesc = false;
 	slot->tts_tuple = NULL;
 	slot->tts_tupleDescriptor = NULL;
 	slot->tts_mcxt = CurrentMemoryContext;
@@ -230,7 +228,7 @@ MakeSingleTupleTableSlot(TupleDesc tupdesc)
 	slot->tts_values = NULL;
 	slot->tts_isnull = NULL;
 
-	ExecSetSlotDescriptor(slot, tupdesc, false);
+	ExecSetSlotDescriptor(slot, tupdesc);
 
 	return slot;
 }
@@ -250,8 +248,8 @@ ExecDropSingleTupleTableSlot(TupleTableSlot *slot)
 	Assert(slot != NULL);
 
 	ExecClearTuple(slot);
-	if (slot->tts_shouldFreeDesc)
-		FreeTupleDesc(slot->tts_tupleDescriptor);
+	if (slot->tts_tupleDescriptor)
+		ReleaseTupleDesc(slot->tts_tupleDescriptor);
 	if (slot->tts_values)
 		pfree(slot->tts_values);
 	if (slot->tts_isnull)
@@ -309,13 +307,15 @@ ExecAllocTableSlot(TupleTable table)
  *		ExecSetSlotDescriptor
  *
  *		This function is used to set the tuple descriptor associated
- *		with the slot's tuple.
+ *		with the slot's tuple.  The passed descriptor must have lifespan
+ *		at least equal to the slot's.  If it is a reference-counted descriptor
+ *		then the reference count is incremented for as long as the slot holds
+ *		a reference.
  * --------------------------------
  */
 void
 ExecSetSlotDescriptor(TupleTableSlot *slot,		/* slot to change */
-					  TupleDesc tupdesc,		/* new tuple descriptor */
-					  bool shouldFree)	/* is desc owned by slot? */
+					  TupleDesc tupdesc)		/* new tuple descriptor */
 {
 	/* For safety, make sure slot is empty before changing it */
 	ExecClearTuple(slot);
@@ -324,8 +324,8 @@ ExecSetSlotDescriptor(TupleTableSlot *slot,		/* slot to change */
 	 * Release any old descriptor.	Also release old Datum/isnull arrays if
 	 * present (we don't bother to check if they could be re-used).
 	 */
-	if (slot->tts_shouldFreeDesc)
-		FreeTupleDesc(slot->tts_tupleDescriptor);
+	if (slot->tts_tupleDescriptor)
+		ReleaseTupleDesc(slot->tts_tupleDescriptor);
 
 	if (slot->tts_values)
 		pfree(slot->tts_values);
@@ -333,10 +333,10 @@ ExecSetSlotDescriptor(TupleTableSlot *slot,		/* slot to change */
 		pfree(slot->tts_isnull);
 
 	/*
-	 * Set up the new descriptor
+	 * Install the new descriptor; if it's refcounted, bump its refcount.
 	 */
 	slot->tts_tupleDescriptor = tupdesc;
-	slot->tts_shouldFreeDesc = shouldFree;
+	PinTupleDesc(tupdesc);
 
 	/*
 	 * Allocate Datum/isnull arrays of the appropriate size.  These must have
@@ -740,7 +740,7 @@ ExecInitNullTupleSlot(EState *estate, TupleDesc tupType)
 {
 	TupleTableSlot *slot = ExecInitExtraTupleSlot(estate);
 
-	ExecSetSlotDescriptor(slot, tupType, false);
+	ExecSetSlotDescriptor(slot, tupType);
 
 	return ExecStoreAllNullTuple(slot);
 }

src/backend/executor/execUtils.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/executor/execUtils.c,v 1.134 2006/04/30 18:30:38 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/executor/execUtils.c,v 1.135 2006/06/16 18:42:22 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -427,12 +427,11 @@ ExecAssignExprContext(EState *estate, PlanState *planstate)
  * ----------------
  */
 void
-ExecAssignResultType(PlanState *planstate,
-					 TupleDesc tupDesc, bool shouldFree)
+ExecAssignResultType(PlanState *planstate, TupleDesc tupDesc)
 {
 	TupleTableSlot *slot = planstate->ps_ResultTupleSlot;
 
-	ExecSetSlotDescriptor(slot, tupDesc, shouldFree);
+	ExecSetSlotDescriptor(slot, tupDesc);
 }
 
 /* ----------------
@@ -461,7 +460,7 @@ ExecAssignResultTypeFromTL(PlanState *planstate)
 	 * to set up planstate->targetlist ...
 	 */
 	tupDesc = ExecTypeFromTL(planstate->plan->targetlist, hasoid);
-	ExecAssignResultType(planstate, tupDesc, true);
+	ExecAssignResultType(planstate, tupDesc);
 }
 
 /* ----------------
@@ -659,12 +658,11 @@ ExecGetScanType(ScanState *scanstate)
  * ----------------
  */
 void
-ExecAssignScanType(ScanState *scanstate,
-				   TupleDesc tupDesc, bool shouldFree)
+ExecAssignScanType(ScanState *scanstate, TupleDesc tupDesc)
 {
 	TupleTableSlot *slot = scanstate->ss_ScanTupleSlot;
 
-	ExecSetSlotDescriptor(slot, tupDesc, shouldFree);
+	ExecSetSlotDescriptor(slot, tupDesc);
 }
 
 /* ----------------
@@ -680,7 +678,7 @@ ExecAssignScanTypeFromOuterPlan(ScanState *scanstate)
 	outerPlan = outerPlanState(scanstate);
 	tupDesc = ExecGetResultType(outerPlan);
 
-	ExecAssignScanType(scanstate, tupDesc, false);
+	ExecAssignScanType(scanstate, tupDesc);
 }
 
 

src/backend/executor/nodeBitmapHeapscan.c

@@ -21,7 +21,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/executor/nodeBitmapHeapscan.c,v 1.11 2006/05/23 15:21:52 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/executor/nodeBitmapHeapscan.c,v 1.12 2006/06/16 18:42:22 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -538,7 +538,7 @@ ExecInitBitmapHeapScan(BitmapHeapScan *node, EState *estate, int eflags)
 	/*
 	 * get the scan type from the relation descriptor.
 	 */
-	ExecAssignScanType(&scanstate->ss, RelationGetDescr(currentRelation), false);
+	ExecAssignScanType(&scanstate->ss, RelationGetDescr(currentRelation));
 
 	/*
 	 * Initialize result tuple type and projection info.

src/backend/executor/nodeFunctionscan.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/executor/nodeFunctionscan.c,v 1.38 2006/03/16 00:31:54 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/executor/nodeFunctionscan.c,v 1.39 2006/06/16 18:42:22 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -220,7 +220,7 @@ ExecInitFunctionScan(FunctionScan *node, EState *estate, int eflags)
 	BlessTupleDesc(tupdesc);
 
 	scanstate->tupdesc = tupdesc;
-	ExecAssignScanType(&scanstate->ss, tupdesc, false);
+	ExecAssignScanType(&scanstate->ss, tupdesc);
 
 	/*
 	 * Other node-specific setup

src/backend/executor/nodeHashjoin.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/executor/nodeHashjoin.c,v 1.81 2006/03/05 15:58:26 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/executor/nodeHashjoin.c,v 1.82 2006/06/16 18:42:22 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -436,8 +436,7 @@ ExecInitHashJoin(HashJoin *node, EState *estate, int eflags)
 	ExecAssignProjectionInfo(&hjstate->js.ps);
 
 	ExecSetSlotDescriptor(hjstate->hj_OuterTupleSlot,
-						  ExecGetResultType(outerPlanState(hjstate)),
-						  false);
+						  ExecGetResultType(outerPlanState(hjstate)));
 
 	/*
 	 * initialize hash-specific info

src/backend/executor/nodeIndexscan.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/executor/nodeIndexscan.c,v 1.113 2006/05/23 15:21:52 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/executor/nodeIndexscan.c,v 1.114 2006/06/16 18:42:22 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -516,7 +516,7 @@ ExecInitIndexScan(IndexScan *node, EState *estate, int eflags)
 	/*
 	 * get the scan type from the relation descriptor.
 	 */
-	ExecAssignScanType(&indexstate->ss, RelationGetDescr(currentRelation), false);
+	ExecAssignScanType(&indexstate->ss, RelationGetDescr(currentRelation));
 
 	/*
 	 * Open the index relation.

src/backend/executor/nodeMergejoin.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/executor/nodeMergejoin.c,v 1.79 2006/03/17 19:38:12 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/executor/nodeMergejoin.c,v 1.80 2006/06/16 18:42:22 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -1552,8 +1552,7 @@ ExecInitMergeJoin(MergeJoin *node, EState *estate, int eflags)
 
 	mergestate->mj_MarkedTupleSlot = ExecInitExtraTupleSlot(estate);
 	ExecSetSlotDescriptor(mergestate->mj_MarkedTupleSlot,
-						  ExecGetResultType(innerPlanState(mergestate)),
-						  false);
+						  ExecGetResultType(innerPlanState(mergestate)));
 
 	switch (node->join.jointype)
 	{

src/backend/executor/nodeSeqscan.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/executor/nodeSeqscan.c,v 1.58 2006/03/05 15:58:26 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/executor/nodeSeqscan.c,v 1.59 2006/06/16 18:42:22 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -159,7 +159,7 @@ InitScanRelation(SeqScanState *node, EState *estate)
 	node->ss_currentRelation = currentRelation;
 	node->ss_currentScanDesc = currentScanDesc;
 
-	ExecAssignScanType(node, RelationGetDescr(currentRelation), false);
+	ExecAssignScanType(node, RelationGetDescr(currentRelation));
 }
 
 

src/backend/executor/nodeSubplan.c

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/executor/nodeSubplan.c,v 1.74 2006/03/05 15:58:26 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/executor/nodeSubplan.c,v 1.75 2006/06/16 18:42:22 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -865,14 +865,14 @@ ExecInitSubPlan(SubPlanState *node, EState *estate, int eflags)
 		 */
 		tupDesc = ExecTypeFromTL(leftptlist, false);
 		slot = ExecAllocTableSlot(tupTable);
-		ExecSetSlotDescriptor(slot, tupDesc, true);
+		ExecSetSlotDescriptor(slot, tupDesc);
 		node->projLeft = ExecBuildProjectionInfo(lefttlist,
 												 NULL,
 												 slot);
 
 		tupDesc = ExecTypeFromTL(rightptlist, false);
 		slot = ExecAllocTableSlot(tupTable);
-		ExecSetSlotDescriptor(slot, tupDesc, true);
+		ExecSetSlotDescriptor(slot, tupDesc);
 		node->projRight = ExecBuildProjectionInfo(righttlist,
 												  node->innerecontext,
 												  slot);

src/backend/executor/nodeSubqueryscan.c

@@ -12,7 +12,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/executor/nodeSubqueryscan.c,v 1.29 2006/03/05 15:58:26 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/executor/nodeSubqueryscan.c,v 1.30 2006/06/16 18:42:22 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -202,11 +202,13 @@ ExecInitSubqueryScan(SubqueryScan *node, EState *estate, int eflags)
 	subquerystate->ss.ps.ps_TupFromTlist = false;
 
 	/*
-	 * Initialize scan tuple type (needed by ExecAssignScanProjectionInfo)
+	 * Initialize scan tuple type (needed by ExecAssignScanProjectionInfo).
+	 * Because the subplan is in its own memory context, we need to copy its
+	 * result tuple type not just link to it; else the tupdesc will disappear
+	 * too soon during shutdown.
 	 */
 	ExecAssignScanType(&subquerystate->ss,
-					   ExecGetResultType(subquerystate->subplan),
-					   false);
+			CreateTupleDescCopy(ExecGetResultType(subquerystate->subplan)));
 
 	/*
 	 * Initialize result tuple type and projection info.

src/backend/executor/nodeTidscan.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/executor/nodeTidscan.c,v 1.48 2006/03/05 15:58:26 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/executor/nodeTidscan.c,v 1.49 2006/06/16 18:42:22 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -524,7 +524,7 @@ ExecInitTidScan(TidScan *node, EState *estate, int eflags)
 	/*
 	 * get the scan type from the relation descriptor.
 	 */
-	ExecAssignScanType(&tidstate->ss, RelationGetDescr(currentRelation), false);
+	ExecAssignScanType(&tidstate->ss, RelationGetDescr(currentRelation));
 
 	/*
 	 * Initialize result tuple type and projection info.

src/backend/optimizer/util/clauses.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/optimizer/util/clauses.c,v 1.211 2006/04/22 01:25:59 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/optimizer/util/clauses.c,v 1.212 2006/06/16 18:42:22 tgl Exp $
  *
  * HISTORY
  *	  AUTHOR			DATE			MAJOR EVENT
@@ -1418,12 +1418,19 @@ rowtype_field_matches(Oid rowtypeid, int fieldnum,
 		return true;
 	tupdesc = lookup_rowtype_tupdesc(rowtypeid, -1);
 	if (fieldnum <= 0 || fieldnum > tupdesc->natts)
+	{
+		ReleaseTupleDesc(tupdesc);
 		return false;
+	}
 	attr = tupdesc->attrs[fieldnum - 1];
 	if (attr->attisdropped ||
 		attr->atttypid != expectedtype ||
 		attr->atttypmod != expectedtypmod)
+	{
+		ReleaseTupleDesc(tupdesc);
 		return false;
+	}
+	ReleaseTupleDesc(tupdesc);
 	return true;
 }
 

src/backend/parser/parse_coerce.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/parser/parse_coerce.c,v 2.138 2006/04/22 01:25:59 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/parser/parse_coerce.c,v 2.139 2006/06/16 18:42:22 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -772,6 +772,8 @@ coerce_record_to_complex(ParseState *pstate, Node *node,
 						format_type_be(targetTypeId)),
 				 errdetail("Input has too many columns.")));
 
+	ReleaseTupleDesc(tupdesc);
+
 	rowexpr = makeNode(RowExpr);
 	rowexpr->args = newargs;
 	rowexpr->row_typeid = targetTypeId;

src/backend/parser/parse_target.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/parser/parse_target.c,v 1.142 2006/03/23 00:19:30 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/parser/parse_target.c,v 1.143 2006/06/16 18:42:22 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -850,7 +850,8 @@ ExpandIndirectionStar(ParseState *pstate, A_Indirection *ind)
 		((Var *) expr)->vartype == RECORDOID)
 		tupleDesc = expandRecordVariable(pstate, (Var *) expr, 0);
 	else if (get_expr_result_type(expr, NULL, &tupleDesc) != TYPEFUNC_COMPOSITE)
-		tupleDesc = lookup_rowtype_tupdesc(exprType(expr), exprTypmod(expr));
+		tupleDesc = lookup_rowtype_tupdesc_copy(exprType(expr),
+												exprTypmod(expr));
 	Assert(tupleDesc);
 
 	/* Generate a list of references to the individual fields */
@@ -1027,7 +1028,8 @@ expandRecordVariable(ParseState *pstate, Var *var, int levelsup)
 	 * appropriate error message while failing.
 	 */
 	if (get_expr_result_type(expr, NULL, &tupleDesc) != TYPEFUNC_COMPOSITE)
-		tupleDesc = lookup_rowtype_tupdesc(exprType(expr), exprTypmod(expr));
+		tupleDesc = lookup_rowtype_tupdesc_copy(exprType(expr),
+												exprTypmod(expr));
 
 	return tupleDesc;
 }

src/backend/utils/adt/rowtypes.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/utils/adt/rowtypes.c,v 1.15 2006/04/04 19:35:36 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/utils/adt/rowtypes.c,v 1.16 2006/06/16 18:42:22 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -264,6 +264,7 @@ record_in(PG_FUNCTION_ARGS)
 	pfree(buf.data);
 	pfree(values);
 	pfree(nulls);
+	ReleaseTupleDesc(tupdesc);
 
 	PG_RETURN_HEAPTUPLEHEADER(result);
 }
@@ -411,6 +412,7 @@ record_out(PG_FUNCTION_ARGS)
 
 	pfree(values);
 	pfree(nulls);
+	ReleaseTupleDesc(tupdesc);
 
 	PG_RETURN_CSTRING(buf.data);
 }
@@ -605,6 +607,7 @@ record_recv(PG_FUNCTION_ARGS)
 	heap_freetuple(tuple);
 	pfree(values);
 	pfree(nulls);
+	ReleaseTupleDesc(tupdesc);
 
 	PG_RETURN_HEAPTUPLEHEADER(result);
 }
@@ -731,6 +734,7 @@ record_send(PG_FUNCTION_ARGS)
 
 	pfree(values);
 	pfree(nulls);
+	ReleaseTupleDesc(tupdesc);
 
 	PG_RETURN_BYTEA_P(pq_endtypsend(&buf));
 }

src/backend/utils/adt/ruleutils.c

@@ -2,7 +2,7 @@
  * ruleutils.c	- Functions to convert stored expressions/querytrees
  *				back to source text
  *
- *	  $PostgreSQL: pgsql/src/backend/utils/adt/ruleutils.c,v 1.223 2006/05/28 21:13:53 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/utils/adt/ruleutils.c,v 1.224 2006/06/16 18:42:22 tgl Exp $
  **********************************************************************/
 
 #include "postgres.h"
@@ -2697,7 +2697,8 @@ get_name_for_var_field(Var *var, int fieldno,
 	 * appropriate error message while failing.
 	 */
 	if (get_expr_result_type(expr, NULL, &tupleDesc) != TYPEFUNC_COMPOSITE)
-		tupleDesc = lookup_rowtype_tupdesc(exprType(expr), exprTypmod(expr));
+		tupleDesc = lookup_rowtype_tupdesc_copy(exprType(expr),
+												exprTypmod(expr));
 
 	/* Got the tupdesc, so we can extract the field name */
 	Assert(fieldno >= 1 && fieldno <= tupleDesc->natts);
@@ -3312,8 +3313,8 @@ get_rule_expr(Node *node, deparse_context *context,
 					TupleDesc	tupdesc;
 
 					if (get_expr_result_type(arg, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
-						tupdesc = lookup_rowtype_tupdesc(exprType(arg),
-														 exprTypmod(arg));
+						tupdesc = lookup_rowtype_tupdesc_copy(exprType(arg),
+															  exprTypmod(arg));
 					Assert(tupdesc);
 					/* Got the tupdesc, so we can extract the field name */
 					Assert(fno >= 1 && fno <= tupdesc->natts);
@@ -3514,6 +3515,8 @@ get_rule_expr(Node *node, deparse_context *context,
 						}
 						i++;
 					}
+
+					ReleaseTupleDesc(tupdesc);
 				}
 				appendStringInfo(buf, ")");
 				if (rowexpr->row_format == COERCE_EXPLICIT_CAST)

src/backend/utils/cache/relcache.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/utils/cache/relcache.c,v 1.241 2006/05/06 15:51:07 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/utils/cache/relcache.c,v 1.242 2006/06/16 18:42:22 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -313,6 +313,8 @@ AllocateRelationDesc(Relation relation, Form_pg_class relp)
 	/* and allocate attribute tuple form storage */
 	relation->rd_att = CreateTemplateTupleDesc(relationForm->relnatts,
 											   relationForm->relhasoids);
+	/* which we mark as a reference-counted tupdesc */
+	relation->rd_att->tdrefcount = 1;
 
 	MemoryContextSwitchTo(oldcxt);
 
@@ -1234,6 +1236,8 @@ formrdesc(const char *relationName, Oid relationReltype,
 	 * defined by macros in src/include/catalog/ headers.
 	 */
 	relation->rd_att = CreateTemplateTupleDesc(natts, hasoids);
+	relation->rd_att->tdrefcount = 1;	/* mark as refcounted */
+
 	relation->rd_att->tdtypeid = relationReltype;
 	relation->rd_att->tdtypmod = -1;	/* unnecessary, but... */
 
@@ -1591,7 +1595,10 @@ RelationClearRelation(Relation relation, bool rebuild)
 	{
 		/* ok to zap remaining substructure */
 		flush_rowtype_cache(old_reltype);
-		FreeTupleDesc(relation->rd_att);
+		/* can't use DecrTupleDescRefCount here */
+		Assert(relation->rd_att->tdrefcount > 0);
+		if (--relation->rd_att->tdrefcount == 0)
+			FreeTupleDesc(relation->rd_att);
 		if (relation->rd_rulescxt)
 			MemoryContextDelete(relation->rd_rulescxt);
 		pfree(relation);
@@ -1601,7 +1608,10 @@ RelationClearRelation(Relation relation, bool rebuild)
 		/*
 		 * When rebuilding an open relcache entry, must preserve ref count and
 		 * rd_createSubid state.  Also attempt to preserve the tupledesc and
-		 * rewrite-rule substructures in place.
+		 * rewrite-rule substructures in place.  (Note: the refcount mechanism
+		 * for tupledescs may eventually ensure that we don't really need to
+		 * preserve the tupledesc in-place, but for now there are still a lot
+		 * of places that assume an open rel's tupledesc won't move.)
 		 *
 		 * Note that this process does not touch CurrentResourceOwner; which
 		 * is good because whatever ref counts the entry may have do not
@@ -1618,7 +1628,9 @@ RelationClearRelation(Relation relation, bool rebuild)
 		{
 			/* Should only get here if relation was deleted */
 			flush_rowtype_cache(old_reltype);
-			FreeTupleDesc(old_att);
+			Assert(old_att->tdrefcount > 0);
+			if (--old_att->tdrefcount == 0)
+				FreeTupleDesc(old_att);
 			if (old_rulescxt)
 				MemoryContextDelete(old_rulescxt);
 			pfree(relation);
@@ -1629,13 +1641,17 @@ RelationClearRelation(Relation relation, bool rebuild)
 		if (equalTupleDescs(old_att, relation->rd_att))
 		{
 			/* needn't flush typcache here */
-			FreeTupleDesc(relation->rd_att);
+			Assert(relation->rd_att->tdrefcount == 1);
+			if (--relation->rd_att->tdrefcount == 0)
+				FreeTupleDesc(relation->rd_att);
 			relation->rd_att = old_att;
 		}
 		else
 		{
 			flush_rowtype_cache(old_reltype);
-			FreeTupleDesc(old_att);
+			Assert(old_att->tdrefcount > 0);
+			if (--old_att->tdrefcount == 0)
+				FreeTupleDesc(old_att);
 		}
 		if (equalRuleLocks(old_rules, relation->rd_rules))
 		{
@@ -2075,6 +2091,7 @@ RelationBuildLocalRelation(const char *relname,
 	 * catalogs.  We can copy attnotnull constraints here, however.
 	 */
 	rel->rd_att = CreateTupleDescCopy(tupDesc);
+	rel->rd_att->tdrefcount = 1;	/* mark as refcounted */
 	has_not_null = false;
 	for (i = 0; i < natts; i++)
 	{
@@ -2996,6 +3013,8 @@ load_relcache_init_file(void)
 		/* initialize attribute tuple forms */
 		rel->rd_att = CreateTemplateTupleDesc(relform->relnatts,
 											  relform->relhasoids);
+		rel->rd_att->tdrefcount = 1;	/* mark as refcounted */
+
 		rel->rd_att->tdtypeid = relform->reltype;
 		rel->rd_att->tdtypmod = -1;		/* unnecessary, but... */
 

src/backend/utils/cache/typcache.c

@@ -36,7 +36,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/utils/cache/typcache.c,v 1.18 2006/03/05 15:58:45 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/utils/cache/typcache.c,v 1.19 2006/06/16 18:42:23 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -270,12 +270,16 @@ lookup_type_cache(Oid type_id, int flags)
 		Assert(rel->rd_rel->reltype == typentry->type_id);
 
 		/*
-		 * Notice that we simply store a link to the relcache's tupdesc. Since
-		 * we are relying on relcache to detect cache flush events, there's
-		 * not a lot of point to maintaining an independent copy.
+		 * Link to the tupdesc and increment its refcount (we assert it's
+		 * a refcounted descriptor).  We don't use IncrTupleDescRefCount()
+		 * for this, because the reference mustn't be entered in the current
+		 * resource owner; it can outlive the current query.
 		 */
 		typentry->tupDesc = RelationGetDescr(rel);
 
+		Assert(typentry->tupDesc->tdrefcount > 0);
+		typentry->tupDesc->tdrefcount++;
+
 		relation_close(rel, AccessShareLock);
 	}
 
@@ -283,29 +287,13 @@ lookup_type_cache(Oid type_id, int flags)
 }
 
 /*
- * lookup_rowtype_tupdesc
- *
- * Given a typeid/typmod that should describe a known composite type,
- * return the tuple descriptor for the type.  Will ereport on failure.
- *
- * Note: returned TupleDesc points to cached copy; caller must copy it
- * if intending to scribble on it or keep a reference for a long time.
- */
-TupleDesc
-lookup_rowtype_tupdesc(Oid type_id, int32 typmod)
-{
-	return lookup_rowtype_tupdesc_noerror(type_id, typmod, false);
-}
-
-/*
- * lookup_rowtype_tupdesc_noerror
+ * lookup_rowtype_tupdesc_internal --- internal routine to lookup a rowtype
  *
- * As above, but if the type is not a known composite type and noError
- * is true, returns NULL instead of ereport'ing.  (Note that if a bogus
- * type_id is passed, you'll get an ereport anyway.)
+ * Same API as lookup_rowtype_tupdesc_noerror, but the returned tupdesc
+ * hasn't had its refcount bumped.
  */
-TupleDesc
-lookup_rowtype_tupdesc_noerror(Oid type_id, int32 typmod, bool noError)
+static TupleDesc
+lookup_rowtype_tupdesc_internal(Oid type_id, int32 typmod, bool noError)
 {
 	if (type_id != RECORDOID)
 	{
@@ -339,6 +327,59 @@ lookup_rowtype_tupdesc_noerror(Oid type_id, int32 typmod, bool noError)
 	}
 }
 
+/*
+ * lookup_rowtype_tupdesc
+ *
+ * Given a typeid/typmod that should describe a known composite type,
+ * return the tuple descriptor for the type.  Will ereport on failure.
+ *
+ * Note: on success, we increment the refcount of the returned TupleDesc,
+ * and log the reference in CurrentResourceOwner.  Caller should call
+ * ReleaseTupleDesc or DecrTupleDescRefCount when done using the tupdesc.
+ */
+TupleDesc
+lookup_rowtype_tupdesc(Oid type_id, int32 typmod)
+{
+	TupleDesc	tupDesc;
+
+	tupDesc = lookup_rowtype_tupdesc_internal(type_id, typmod, false);
+	IncrTupleDescRefCount(tupDesc);
+	return tupDesc;
+}
+
+/*
+ * lookup_rowtype_tupdesc_noerror
+ *
+ * As above, but if the type is not a known composite type and noError
+ * is true, returns NULL instead of ereport'ing.  (Note that if a bogus
+ * type_id is passed, you'll get an ereport anyway.)
+ */
+TupleDesc
+lookup_rowtype_tupdesc_noerror(Oid type_id, int32 typmod, bool noError)
+{
+	TupleDesc	tupDesc;
+
+	tupDesc = lookup_rowtype_tupdesc_internal(type_id, typmod, noError);
+	if (tupDesc != NULL)
+		IncrTupleDescRefCount(tupDesc);
+	return tupDesc;
+}
+
+/*
+ * lookup_rowtype_tupdesc_copy
+ *
+ * Like lookup_rowtype_tupdesc(), but the returned TupleDesc has been
+ * copied into the CurrentMemoryContext and is not reference-counted.
+ */
+TupleDesc
+lookup_rowtype_tupdesc_copy(Oid type_id, int32 typmod)
+{
+	TupleDesc tmp;
+
+	tmp = lookup_rowtype_tupdesc_internal(type_id, typmod, false);
+	return CreateTupleDescCopyConstr(tmp);
+}
+
 
 /*
  * assign_record_type_typmod
@@ -425,6 +466,8 @@ assign_record_type_typmod(TupleDesc tupDesc)
 	/* if fail in subrs, no damage except possibly some wasted memory... */
 	entDesc = CreateTupleDescCopy(tupDesc);
 	recentry->tupdescs = lcons(entDesc, recentry->tupdescs);
+	/* mark it as a reference-counted tupdesc */
+	entDesc->tdrefcount = 1;
 	/* now it's safe to advance NextRecordTypmod */
 	newtypmod = NextRecordTypmod++;
 	entDesc->tdtypmod = newtypmod;
@@ -456,6 +499,17 @@ flush_rowtype_cache(Oid type_id)
 											  HASH_FIND, NULL);
 	if (typentry == NULL)
 		return;					/* no matching entry */
+	if (typentry->tupDesc == NULL)
+		return;					/* tupdesc hasn't been requested */
+
+	/*
+	 * Release our refcount and free the tupdesc if none remain.
+	 * (Can't use DecrTupleDescRefCount because this reference is not
+	 * logged in current resource owner.)
+	 */
+	Assert(typentry->tupDesc->tdrefcount > 0);
+	if (--typentry->tupDesc->tdrefcount == 0)
+		FreeTupleDesc(typentry->tupDesc);
 
 	typentry->tupDesc = NULL;
 }

src/backend/utils/fmgr/funcapi.c

@@ -7,7 +7,7 @@
  * Copyright (c) 2002-2006, PostgreSQL Global Development Group
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/utils/fmgr/funcapi.c,v 1.29 2006/03/05 15:58:46 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/utils/fmgr/funcapi.c,v 1.30 2006/06/16 18:42:23 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -185,8 +185,7 @@ shutdown_MultiFuncCall(Datum arg)
  *		receives the actual datatype OID (this is mainly useful for scalar
  *		result types).	If resultTupleDesc isn't NULL, *resultTupleDesc
  *		receives a pointer to a TupleDesc when the result is of a composite
- *		type, or NULL when it's a scalar result.  NB: the tupledesc should
- *		be copied if it is to be accessed over a long period.
+ *		type, or NULL when it's a scalar result.
  *
  * One hard case that this handles is resolution of actual rowtypes for
  * functions returning RECORD (from either the function's OUT parameter
@@ -246,7 +245,7 @@ get_expr_result_type(Node *expr,
 			*resultTupleDesc = NULL;
 		result = get_type_func_class(typid);
 		if (result == TYPEFUNC_COMPOSITE && resultTupleDesc)
-			*resultTupleDesc = lookup_rowtype_tupdesc(typid, -1);
+			*resultTupleDesc = lookup_rowtype_tupdesc_copy(typid, -1);
 	}
 
 	return result;
@@ -363,7 +362,7 @@ internal_get_result_type(Oid funcid,
 	{
 		case TYPEFUNC_COMPOSITE:
 			if (resultTupleDesc)
-				*resultTupleDesc = lookup_rowtype_tupdesc(rettype, -1);
+				*resultTupleDesc = lookup_rowtype_tupdesc_copy(rettype, -1);
 			/* Named composite types can't have any polymorphic columns */
 			break;
 		case TYPEFUNC_SCALAR:
@@ -1053,7 +1052,7 @@ TypeGetTupleDesc(Oid typeoid, List *colaliases)
 	if (functypclass == TYPEFUNC_COMPOSITE)
 	{
 		/* Composite data type, e.g. a table's row type */
-		tupdesc = CreateTupleDescCopy(lookup_rowtype_tupdesc(typeoid, -1));
+		tupdesc = lookup_rowtype_tupdesc_copy(typeoid, -1);
 
 		if (colaliases != NIL)
 		{

src/backend/utils/resowner/README

-$PostgreSQL: pgsql/src/backend/utils/resowner/README,v 1.3 2004/08/25 18:43:43 tgl Exp $
+$PostgreSQL: pgsql/src/backend/utils/resowner/README,v 1.4 2006/06/16 18:42:23 tgl Exp $
 
 Notes about resource owners
 ---------------------------
@@ -61,9 +61,9 @@ ResourceOwner transfers lock ownership to the parent instead of actually
 releasing the lock, if isCommit is true.
 
 Currently, ResourceOwners contain direct support for recording ownership
-of buffer pins, lmgr locks, and catcache and relcache references.  Other
-objects can be associated with a ResourceOwner by recording the address of
-the owning ResourceOwner in such an object.  There is an API for other
+of buffer pins, lmgr locks, and catcache, relcache, and tupdesc references.
+Other objects can be associated with a ResourceOwner by recording the address
+of the owning ResourceOwner in such an object.  There is an API for other
 modules to get control during ResourceOwner release, so that they can scan
 their own data structures to find the objects that need to be deleted.
 

src/backend/utils/resowner/resowner.c

@@ -14,7 +14,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/utils/resowner/resowner.c,v 1.19 2006/04/03 13:44:33 teodor Exp $
+ *	  $PostgreSQL: pgsql/src/backend/utils/resowner/resowner.c,v 1.20 2006/06/16 18:42:23 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -57,6 +57,11 @@ typedef struct ResourceOwnerData
 	int			nrelrefs;		/* number of owned relcache pins */
 	Relation   *relrefs;		/* dynamically allocated array */
 	int			maxrelrefs;		/* currently allocated array size */
+
+	/* We have built-in support for remembering tupdesc references */
+	int			ntupdescs;		/* number of owned tupdesc references */
+	TupleDesc  *tupdescs;		/* dynamically allocated array */
+	int			maxtupdescs;	/* currently allocated array size */
 } ResourceOwnerData;
 
 
@@ -87,6 +92,7 @@ static void ResourceOwnerReleaseInternal(ResourceOwner owner,
 							 bool isCommit,
 							 bool isTopLevel);
 static void PrintRelCacheLeakWarning(Relation rel);
+static void PrintTupleDescLeakWarning(TupleDesc tupdesc);
 
 
 /*****************************************************************************
@@ -258,7 +264,7 @@ ResourceOwnerReleaseInternal(ResourceOwner owner,
 		/*
 		 * Release catcache references.  Note that ReleaseCatCache will remove
 		 * the catref entry from my list, so I just have to iterate till there
-		 * are none.  Ditto for catcache lists.
+		 * are none.
 		 *
 		 * As with buffer pins, warn if any are left at commit time, and
 		 * release back-to-front for speed.
@@ -269,12 +275,20 @@ ResourceOwnerReleaseInternal(ResourceOwner owner,
 				PrintCatCacheLeakWarning(owner->catrefs[owner->ncatrefs - 1]);
 			ReleaseCatCache(owner->catrefs[owner->ncatrefs - 1]);
 		}
+		/* Ditto for catcache lists */
 		while (owner->ncatlistrefs > 0)
 		{
 			if (isCommit)
 				PrintCatCacheListLeakWarning(owner->catlistrefs[owner->ncatlistrefs - 1]);
 			ReleaseCatCacheList(owner->catlistrefs[owner->ncatlistrefs - 1]);
 		}
+		/* Ditto for tupdesc references */
+		while (owner->ntupdescs > 0)
+		{
+			if (isCommit)
+				PrintTupleDescLeakWarning(owner->tupdescs[owner->ntupdescs - 1]);
+			DecrTupleDescRefCount(owner->tupdescs[owner->ntupdescs - 1]);
+		}
 
 		/* Clean up index scans too */
 		ReleaseResources_hash();
@@ -304,6 +318,7 @@ ResourceOwnerDelete(ResourceOwner owner)
 	Assert(owner->ncatrefs == 0);
 	Assert(owner->ncatlistrefs == 0);
 	Assert(owner->nrelrefs == 0);
+	Assert(owner->ntupdescs == 0);
 
 	/*
 	 * Delete children.  The recursive call will delink the child from me, so
@@ -328,6 +343,8 @@ ResourceOwnerDelete(ResourceOwner owner)
 		pfree(owner->catlistrefs);
 	if (owner->relrefs)
 		pfree(owner->relrefs);
+	if (owner->tupdescs)
+		pfree(owner->tupdescs);
 
 	pfree(owner);
 }
@@ -742,3 +759,85 @@ PrintRelCacheLeakWarning(Relation rel)
 	elog(WARNING, "relcache reference leak: relation \"%s\" not closed",
 		 RelationGetRelationName(rel));
 }
+
+/*
+ * Make sure there is room for at least one more entry in a ResourceOwner's
+ * tupdesc reference array.
+ *
+ * This is separate from actually inserting an entry because if we run out
+ * of memory, it's critical to do so *before* acquiring the resource.
+ */
+void
+ResourceOwnerEnlargeTupleDescs(ResourceOwner owner)
+{
+	int			newmax;
+
+	if (owner->ntupdescs < owner->maxtupdescs)
+		return;					/* nothing to do */
+
+	if (owner->tupdescs == NULL)
+	{
+		newmax = 16;
+		owner->tupdescs = (TupleDesc *)
+			MemoryContextAlloc(TopMemoryContext, newmax * sizeof(TupleDesc));
+		owner->maxtupdescs = newmax;
+	}
+	else
+	{
+		newmax = owner->maxtupdescs * 2;
+		owner->tupdescs = (TupleDesc *)
+			repalloc(owner->tupdescs, newmax * sizeof(TupleDesc));
+		owner->maxtupdescs = newmax;
+	}
+}
+
+/*
+ * Remember that a tupdesc reference is owned by a ResourceOwner
+ *
+ * Caller must have previously done ResourceOwnerEnlargeTupleDescs()
+ */
+void
+ResourceOwnerRememberTupleDesc(ResourceOwner owner, TupleDesc tupdesc)
+{
+	Assert(owner->ntupdescs < owner->maxtupdescs);
+	owner->tupdescs[owner->ntupdescs] = tupdesc;
+	owner->ntupdescs++;
+}
+
+/*
+ * Forget that a tupdesc reference is owned by a ResourceOwner
+ */
+void
+ResourceOwnerForgetTupleDesc(ResourceOwner owner, TupleDesc tupdesc)
+{
+	TupleDesc  *tupdescs = owner->tupdescs;
+	int			nt1 = owner->ntupdescs - 1;
+	int			i;
+
+	for (i = nt1; i >= 0; i--)
+	{
+		if (tupdescs[i] == tupdesc)
+		{
+			while (i < nt1)
+			{
+				tupdescs[i] = tupdescs[i + 1];
+				i++;
+			}
+			owner->ntupdescs = nt1;
+			return;
+		}
+	}
+	elog(ERROR, "tupdesc reference %p is not owned by resource owner %s",
+		 tupdesc, owner->name);
+}
+
+/*
+ * Debugging subroutine
+ */
+static void
+PrintTupleDescLeakWarning(TupleDesc tupdesc)
+{
+	elog(WARNING,
+		 "TupleDesc reference leak: TupleDesc %p (%u,%d) still referenced",
+		 tupdesc, tupdesc->tdtypeid, tupdesc->tdtypmod);
+}

src/include/access/tupdesc.h

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2006, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/access/tupdesc.h,v 1.49 2006/03/16 00:31:55 tgl Exp $
+ * $PostgreSQL: pgsql/src/include/access/tupdesc.h,v 1.50 2006/06/16 18:42:23 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -57,6 +57,14 @@ typedef struct tupleConstr
  * tdtypeid is RECORDOID, and tdtypmod can be either -1 for a fully anonymous
  * row type, or a value >= 0 to allow the rowtype to be looked up in the
  * typcache.c type cache.
+ *
+ * Tuple descriptors that live in caches (relcache or typcache, at present)
+ * are reference-counted: they can be deleted when their reference count goes
+ * to zero.  Tuple descriptors created by the executor need no reference
+ * counting, however: they are simply created in the appropriate memory
+ * context and go away when the context is freed.  We set the tdrefcount
+ * field of such a descriptor to -1, while reference-counted descriptors
+ * always have tdrefcount >= 0.
  */
 typedef struct tupleDesc
 {
@@ -67,6 +75,7 @@ typedef struct tupleDesc
 	Oid			tdtypeid;		/* composite type ID for tuple type */
 	int32		tdtypmod;		/* typmod for tuple type */
 	bool		tdhasoid;		/* tuple has oid attribute in its header */
+	int			tdrefcount;		/* reference count, or -1 if not counting */
 }	*TupleDesc;
 
 
@@ -81,6 +90,21 @@ extern TupleDesc CreateTupleDescCopyConstr(TupleDesc tupdesc);
 
 extern void FreeTupleDesc(TupleDesc tupdesc);
 
+extern void IncrTupleDescRefCount(TupleDesc tupdesc);
+extern void DecrTupleDescRefCount(TupleDesc tupdesc);
+
+#define PinTupleDesc(tupdesc) \
+	do { \
+		if ((tupdesc)->tdrefcount >= 0) \
+			IncrTupleDescRefCount(tupdesc); \
+	} while (0)
+
+#define ReleaseTupleDesc(tupdesc) \
+	do { \
+		if ((tupdesc)->tdrefcount >= 0) \
+			DecrTupleDescRefCount(tupdesc); \
+	} while (0)
+  
 extern bool equalTupleDescs(TupleDesc tupdesc1, TupleDesc tupdesc2);
 
 extern void TupleDescInitEntry(TupleDesc desc,

src/include/executor/executor.h

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2006, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/executor/executor.h,v 1.126 2006/03/05 15:58:56 momjian Exp $
+ * $PostgreSQL: pgsql/src/include/executor/executor.h,v 1.127 2006/06/16 18:42:23 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -249,8 +249,7 @@ extern ExprContext *MakePerTupleExprContext(EState *estate);
 	} while (0)
 
 extern void ExecAssignExprContext(EState *estate, PlanState *planstate);
-extern void ExecAssignResultType(PlanState *planstate,
-					 TupleDesc tupDesc, bool shouldFree);
+extern void ExecAssignResultType(PlanState *planstate, TupleDesc tupDesc);
 extern void ExecAssignResultTypeFromTL(PlanState *planstate);
 extern TupleDesc ExecGetResultType(PlanState *planstate);
 extern ProjectionInfo *ExecBuildProjectionInfo(List *targetList,
@@ -259,8 +258,7 @@ extern ProjectionInfo *ExecBuildProjectionInfo(List *targetList,
 extern void ExecAssignProjectionInfo(PlanState *planstate);
 extern void ExecFreeExprContext(PlanState *planstate);
 extern TupleDesc ExecGetScanType(ScanState *scanstate);
-extern void ExecAssignScanType(ScanState *scanstate,
-				   TupleDesc tupDesc, bool shouldFree);
+extern void ExecAssignScanType(ScanState *scanstate, TupleDesc tupDesc);
 extern void ExecAssignScanTypeFromOuterPlan(ScanState *scanstate);
 
 extern bool ExecRelationIsTargetRelation(EState *estate, Index scanrelid);

src/include/executor/tuptable.h

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2006, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/executor/tuptable.h,v 1.30 2006/03/05 15:58:56 momjian Exp $
+ * $PostgreSQL: pgsql/src/include/executor/tuptable.h,v 1.31 2006/06/16 18:42:23 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -15,6 +15,7 @@
 #define TUPTABLE_H
 
 #include "access/htup.h"
+#include "access/tupdesc.h"
 
 
 /*----------
@@ -56,13 +57,17 @@
  * TRUE, tts_shouldFree FALSE, tts_tuple NULL, tts_buffer InvalidBuffer,
  * and tts_nvalid zero.
  *
+ * The tupleDescriptor is simply referenced, not copied, by the TupleTableSlot
+ * code.  The caller of ExecSetSlotDescriptor() is responsible for providing
+ * a descriptor that will live as long as the slot does.  (Typically, both
+ * slots and descriptors are in per-query memory and are freed by memory
+ * context deallocation at query end; so it's not worth providing any extra
+ * mechanism to do more.  However, the slot will increment the tupdesc
+ * reference count if a reference-counted tupdesc is supplied.)
+ *
  * When tts_shouldFree is true, the physical tuple is "owned" by the slot
  * and should be freed when the slot's reference to the tuple is dropped.
  *
- * tts_shouldFreeDesc is similar to tts_shouldFree: if it's true, then the
- * tupleDescriptor is "owned" by the TupleTableSlot and should be
- * freed when the slot's reference to the descriptor is dropped.
- *
  * If tts_buffer is not InvalidBuffer, then the slot is holding a pin
  * on the indicated buffer page; drop the pin when we release the
  * slot's reference to that buffer.  (tts_shouldFree should always be
@@ -87,7 +92,6 @@ typedef struct TupleTableSlot
 	NodeTag		type;			/* vestigial ... allows IsA tests */
 	bool		tts_isempty;	/* true = slot is empty */
 	bool		tts_shouldFree; /* should pfree tuple? */
-	bool		tts_shouldFreeDesc;		/* should pfree descriptor? */
 	bool		tts_slow;		/* saved state for slot_deform_tuple */
 	HeapTuple	tts_tuple;		/* physical tuple, or NULL if none */
 	TupleDesc	tts_tupleDescriptor;	/* slot's tuple descriptor */
@@ -124,8 +128,7 @@ extern void ExecDropTupleTable(TupleTable table, bool shouldFree);
 extern TupleTableSlot *MakeSingleTupleTableSlot(TupleDesc tupdesc);
 extern void ExecDropSingleTupleTableSlot(TupleTableSlot *slot);
 extern TupleTableSlot *ExecAllocTableSlot(TupleTable table);
-extern void ExecSetSlotDescriptor(TupleTableSlot *slot,
-					  TupleDesc tupdesc, bool shouldFree);
+extern void ExecSetSlotDescriptor(TupleTableSlot *slot, TupleDesc tupdesc);
 extern TupleTableSlot *ExecStoreTuple(HeapTuple tuple,
 			   TupleTableSlot *slot,
 			   Buffer buffer,

src/include/utils/resowner.h

@@ -12,13 +12,14 @@
  * Portions Copyright (c) 1996-2006, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/utils/resowner.h,v 1.6 2006/03/05 15:59:07 momjian Exp $
+ * $PostgreSQL: pgsql/src/include/utils/resowner.h,v 1.7 2006/06/16 18:42:23 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
 #ifndef RESOWNER_H
 #define RESOWNER_H
 
+#include "access/tupdesc.h"
 #include "storage/buf.h"
 #include "utils/catcache.h"
 #include "utils/rel.h"
@@ -107,4 +108,11 @@ extern void ResourceOwnerRememberRelationRef(ResourceOwner owner,
 extern void ResourceOwnerForgetRelationRef(ResourceOwner owner,
 							   Relation rel);
 
+/* support for tupledesc refcount management */
+extern void ResourceOwnerEnlargeTupleDescs(ResourceOwner owner);
+extern void ResourceOwnerRememberTupleDesc(ResourceOwner owner,
+										   TupleDesc tupdesc);
+extern void ResourceOwnerForgetTupleDesc(ResourceOwner owner,
+										 TupleDesc tupdesc);
+
 #endif   /* RESOWNER_H */

src/include/utils/typcache.h

@@ -9,7 +9,7 @@
  * Portions Copyright (c) 1996-2006, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/utils/typcache.h,v 1.10 2006/03/05 15:59:08 momjian Exp $
+ * $PostgreSQL: pgsql/src/include/utils/typcache.h,v 1.11 2006/06/16 18:42:23 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -58,7 +58,7 @@ typedef struct TypeCacheEntry
 	/*
 	 * Tuple descriptor if it's a composite type (row type).  NULL if not
 	 * composite or information hasn't yet been requested.  (NOTE: this is
-	 * actually just a link to information maintained by relcache.c.)
+	 * a reference-counted tupledesc.)
 	 */
 	TupleDesc	tupDesc;
 } TypeCacheEntry;
@@ -79,6 +79,8 @@ extern TupleDesc lookup_rowtype_tupdesc(Oid type_id, int32 typmod);
 extern TupleDesc lookup_rowtype_tupdesc_noerror(Oid type_id, int32 typmod,
 							   bool noError);
 
+extern TupleDesc lookup_rowtype_tupdesc_copy(Oid type_id, int32 typmod);
+
 extern void assign_record_type_typmod(TupleDesc tupDesc);
 
 extern void flush_rowtype_cache(Oid type_id);

src/pl/plperl/plperl.c

 /**********************************************************************
  * plperl.c - perl as a procedural language for PostgreSQL
  *
- *	  $PostgreSQL: pgsql/src/pl/plperl/plperl.c,v 1.111 2006/05/30 22:12:15 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/pl/plperl/plperl.c,v 1.112 2006/06/16 18:42:23 tgl Exp $
  *
  **********************************************************************/
 
@@ -904,6 +904,7 @@ plperl_call_perl_func(plperl_proc_desc *desc, FunctionCallInfo fcinfo)
 
 			hashref = plperl_hash_from_tuple(&tmptup, tupdesc);
 			XPUSHs(sv_2mortal(hashref));
+			ReleaseTupleDesc(tupdesc);
 		}
 		else
 		{

src/pl/plpgsql/src/pl_exec.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/pl/plpgsql/src/pl_exec.c,v 1.171 2006/06/15 18:02:22 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/pl/plpgsql/src/pl_exec.c,v 1.172 2006/06/16 18:42:23 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -233,6 +233,7 @@ plpgsql_exec_function(PLpgSQL_function *func, FunctionCallInfo fcinfo)
 						tmptup.t_tableOid = InvalidOid;
 						tmptup.t_data = td;
 						exec_move_row(&estate, NULL, row, &tmptup, tupdesc);
+						ReleaseTupleDesc(tupdesc);
 					}
 					else
 					{
@@ -1701,10 +1702,11 @@ exec_stmt_select(PLpgSQL_execstate *estate, PLpgSQL_stmt_select *stmt)
 
 	/*
 	 * Run the query
+	 *
 	 * Retrieving two rows can be slower than a single row, e.g. 
 	 * a sequential scan where the scan has to be completed to
-	 * check for a second row.  For this reason, we only do the
-	 * second-line check for STRICT.
+	 * check for a second row.  For this reason, we only retrieve
+	 * the second row if checking STRICT.
 	 */
 	exec_run_select(estate, stmt->query, stmt->strict ? 2 : 1, NULL);
 	tuptab = estate->eval_tuptable;
@@ -1717,22 +1719,21 @@ exec_stmt_select(PLpgSQL_execstate *estate, PLpgSQL_stmt_select *stmt)
 	 */
 	if (n == 0)
 	{
-		if (!stmt->strict)
-		{
-			/* null the target */
-			exec_move_row(estate, rec, row, NULL, tuptab->tupdesc);
-			exec_eval_cleanup(estate);
-			return PLPGSQL_RC_OK;
-		}
-		else
+		if (stmt->strict)
 			ereport(ERROR,
-				(errcode(ERRCODE_NO_DATA),
-				 errmsg("query returned no rows")));
+					(errcode(ERRCODE_NO_DATA),
+					 errmsg("query returned no rows")));
+
+		/* set the target to NULL(s) */
+		exec_move_row(estate, rec, row, NULL, tuptab->tupdesc);
+		exec_eval_cleanup(estate);
+		return PLPGSQL_RC_OK;
 	}
-	else if (n > 1 && stmt->strict)
+
+	if (n > 1 && stmt->strict)
 		ereport(ERROR,
-			(errcode(ERRCODE_CARDINALITY_VIOLATION),
-			 errmsg("query more than one row")));
+				(errcode(ERRCODE_CARDINALITY_VIOLATION),
+				 errmsg("query returned more than one row")));
 
 	/*
 	 * Put the first result into the target and set found to true
@@ -3138,6 +3139,7 @@ exec_assign_value(PLpgSQL_execstate *estate,
 					tmptup.t_tableOid = InvalidOid;
 					tmptup.t_data = td;
 					exec_move_row(estate, NULL, row, &tmptup, tupdesc);
+					ReleaseTupleDesc(tupdesc);
 				}
 				break;
 			}
@@ -3180,6 +3182,7 @@ exec_assign_value(PLpgSQL_execstate *estate,
 					tmptup.t_tableOid = InvalidOid;
 					tmptup.t_data = td;
 					exec_move_row(estate, rec, NULL, &tmptup, tupdesc);
+					ReleaseTupleDesc(tupdesc);
 				}
 				break;
 			}

src/pl/plpython/plpython.c

 /**********************************************************************
  * plpython.c - python as a procedural language for PostgreSQL
  *
- *	$PostgreSQL: pgsql/src/pl/plpython/plpython.c,v 1.81 2006/05/30 22:12:16 tgl Exp $
+ *	$PostgreSQL: pgsql/src/pl/plpython/plpython.c,v 1.82 2006/06/16 18:42:23 tgl Exp $
  *
  *********************************************************************
  */
@@ -883,6 +883,7 @@ PLy_function_build_args(FunctionCallInfo fcinfo, PLyProcedure * proc)
 					tmptup.t_data = td;
 
 					arg = PLyDict_FromTuple(&(proc->args[i]), &tmptup, tupdesc);
+					ReleaseTupleDesc(tupdesc);
 				}
 			}
 			else

src/pl/tcl/pltcl.c

@@ -2,7 +2,7 @@
  * pltcl.c		- PostgreSQL support for Tcl as
  *				  procedural language (PL)
  *
- *	  $PostgreSQL: pgsql/src/pl/tcl/pltcl.c,v 1.104 2006/05/30 22:12:16 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/pl/tcl/pltcl.c,v 1.105 2006/06/16 18:42:24 tgl Exp $
  *
  **********************************************************************/
 
@@ -511,6 +511,7 @@ pltcl_func_handler(PG_FUNCTION_ARGS)
 					pltcl_build_tuple_argument(&tmptup, tupdesc, &list_tmp);
 					Tcl_DStringAppendElement(&tcl_cmd,
 											 Tcl_DStringValue(&list_tmp));
+					ReleaseTupleDesc(tupdesc);
 				}
 			}
 			else