3 files changed, 19 insertions, 55 deletions

diff --git a/src/backend/executor/execQual.c b/src/backend/executor/execQual.c
index c0ca58bbb4d..01e04d3b14e 100644
--- a/src/backend/executor/execQual.c
+++ b/src/backend/executor/execQual.c
@@ -5350,15 +5350,24 @@ ExecCleanTargetListLength(List *targetlist)
  * of *isDone = ExprMultipleResult signifies a set element, and a return
  * of *isDone = ExprEndResult signifies end of the set of tuple.
  * We assume that *isDone has been initialized to ExprSingleResult by caller.
+ *
+ * Since fields of the result tuple might be multiply referenced in higher
+ * plan nodes, we have to force any read/write expanded values to read-only
+ * status.  It's a bit annoying to have to do that for every projected
+ * expression; in the future, consider teaching the planner to detect
+ * actually-multiply-referenced Vars and insert an expression node that
+ * would do that only where really required.
  */
 static bool
 ExecTargetList(List *targetlist,
+			   TupleDesc tupdesc,
 			   ExprContext *econtext,
 			   Datum *values,
 			   bool *isnull,
 			   ExprDoneCond *itemIsDone,
 			   ExprDoneCond *isDone)
 {
+	Form_pg_attribute *att = tupdesc->attrs;
 	MemoryContext oldContext;
 	ListCell   *tl;
 	bool		haveDoneSets;
@@ -5384,6 +5393,10 @@ ExecTargetList(List *targetlist,
 									  &isnull[resind],
 									  &itemIsDone[resind]);
 
+		values[resind] = MakeExpandedObjectReadOnly(values[resind],
+													isnull[resind],
+													att[resind]->attlen);
+
 		if (itemIsDone[resind] != ExprSingleResult)
 		{
 			/* We have a set-valued expression in the tlist */
@@ -5437,6 +5450,10 @@ ExecTargetList(List *targetlist,
 												  &isnull[resind],
 												  &itemIsDone[resind]);
 
+					values[resind] = MakeExpandedObjectReadOnly(values[resind],
+															  isnull[resind],
+														att[resind]->attlen);
+
 					if (itemIsDone[resind] == ExprEndResult)
 					{
 						/*
@@ -5470,6 +5487,7 @@ ExecTargetList(List *targetlist,
 													  econtext,
 													  &isnull[resind],
 													  &itemIsDone[resind]);
+						/* no need for MakeExpandedObjectReadOnly */
 					}
 				}
 
@@ -5595,6 +5613,7 @@ ExecProject(ProjectionInfo *projInfo, ExprDoneCond *isDone)
 	if (projInfo->pi_targetlist)
 	{
 		if (!ExecTargetList(projInfo->pi_targetlist,
+							slot->tts_tupleDescriptor,
 							econtext,
 							slot->tts_values,
 							slot->tts_isnull,
diff --git a/src/backend/executor/execTuples.c b/src/backend/executor/execTuples.c
index dfe56226568..2b81f60a519 100644
--- a/src/backend/executor/execTuples.c
+++ b/src/backend/executor/execTuples.c
@@ -88,7 +88,6 @@
 #include "nodes/nodeFuncs.h"
 #include "storage/bufmgr.h"
 #include "utils/builtins.h"
-#include "utils/expandeddatum.h"
 #include "utils/lsyscache.h"
 #include "utils/typcache.h"
 
@@ -813,52 +812,6 @@ ExecCopySlot(TupleTableSlot *dstslot, TupleTableSlot *srcslot)
 	return ExecStoreTuple(newTuple, dstslot, InvalidBuffer, true);
 }
 
-/* --------------------------------
- *		ExecMakeSlotContentsReadOnly
- *			Mark any R/W expanded datums in the slot as read-only.
- *
- * This is needed when a slot that might contain R/W datum references is to be
- * used as input for general expression evaluation.  Since the expression(s)
- * might contain more than one Var referencing the same R/W datum, we could
- * get wrong answers if functions acting on those Vars thought they could
- * modify the expanded value in-place.
- *
- * For notational reasons, we return the same slot passed in.
- * --------------------------------
- */
-TupleTableSlot *
-ExecMakeSlotContentsReadOnly(TupleTableSlot *slot)
-{
-	/*
-	 * sanity checks
-	 */
-	Assert(slot != NULL);
-	Assert(slot->tts_tupleDescriptor != NULL);
-	Assert(!slot->tts_isempty);
-
-	/*
-	 * If the slot contains a physical tuple, it can't contain any expanded
-	 * datums, because we flatten those when making a physical tuple.  This
-	 * might change later; but for now, we need do nothing unless the slot is
-	 * virtual.
-	 */
-	if (slot->tts_tuple == NULL)
-	{
-		Form_pg_attribute *att = slot->tts_tupleDescriptor->attrs;
-		int			attnum;
-
-		for (attnum = 0; attnum < slot->tts_nvalid; attnum++)
-		{
-			slot->tts_values[attnum] =
-				MakeExpandedObjectReadOnly(slot->tts_values[attnum],
-										   slot->tts_isnull[attnum],
-										   att[attnum]->attlen);
-		}
-	}
-
-	return slot;
-}
-
 
 /* ----------------------------------------------------------------
  *				convenience initialization routines
diff --git a/src/backend/executor/nodeSubqueryscan.c b/src/backend/executor/nodeSubqueryscan.c
index 0304b15b158..9bafc626772 100644
--- a/src/backend/executor/nodeSubqueryscan.c
+++ b/src/backend/executor/nodeSubqueryscan.c
@@ -56,15 +56,7 @@ SubqueryNext(SubqueryScanState *node)
 	 * We just return the subplan's result slot, rather than expending extra
 	 * cycles for ExecCopySlot().  (Our own ScanTupleSlot is used only for
 	 * EvalPlanQual rechecks.)
-	 *
-	 * We do need to mark the slot contents read-only to prevent interference
-	 * between different functions reading the same datum from the slot. It's
-	 * a bit hokey to do this to the subplan's slot, but should be safe
-	 * enough.
 	 */
-	if (!TupIsNull(slot))
-		slot = ExecMakeSlotContentsReadOnly(slot);
-
 	return slot;
 }