Put back code in nodeAgg to generate a dummy all-nulls input tuple

before calling execProject, when the outerPlan has returned zero tuples.
I took this out under the mistaken impression that the input tuple
couldn't be referenced by execProject if we weren't in GROUP BY mode.
But it can, if we're in an UPDATE or DELETE...

src/backend/executor/nodeAgg.c

@@ -11,7 +11,7 @@
  *	  SQL aggregates. (Do not expect POSTQUEL semantics.)	 -- ay 2/95
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/executor/nodeAgg.c,v 1.57 1999/10/08 03:49:55 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/executor/nodeAgg.c,v 1.58 1999/10/30 01:18:16 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -408,24 +408,43 @@ ExecAgg(Agg *node)
 				return NULL;
 		}
 		else
+		{
 			aggstate->agg_done = true;
+			/*
+			 * If inputtuple==NULL (ie, the outerPlan didn't return anything),
+			 * create a dummy all-nulls input tuple for use by execProject.
+			 * 99.44% of the time this is a waste of cycles, because
+			 * ordinarily the projected output tuple's targetlist cannot
+			 * contain any direct (non-aggregated) references to input
+			 * columns, so the dummy tuple will not be referenced.  However
+			 * there are special cases where this isn't so --- in particular
+			 * an UPDATE involving an aggregate will have a targetlist
+			 * reference to ctid.  We need to return a null for ctid in that
+			 * situation, not coredump.
+			 *
+			 * The values returned for the aggregates will be the initial
+			 * values of the transition functions.
+			 */
+			if (inputTuple == NULL)
+			{
+				TupleDesc	tupType;
+				Datum	   *tupValue;
+				char	   *null_array;
+				AttrNumber	attnum;
+
+				tupType = aggstate->csstate.css_ScanTupleSlot->ttc_tupleDescriptor;
+				tupValue = projInfo->pi_tupValue;
+				null_array = (char *) palloc(sizeof(char) * tupType->natts);
+				for (attnum = 0; attnum < tupType->natts; attnum++)
+					null_array[attnum] = 'n';
+				inputTuple = heap_formtuple(tupType, tupValue, null_array);
+				pfree(null_array);
+			}
+		}
 
 		/*
-		 * We used to create a dummy all-nulls input tuple here if
-		 * inputTuple == NULL (ie, the outerPlan didn't return anything).
-		 * However, now that we don't return a bogus tuple in Group mode,
-		 * we can only get here with inputTuple == NULL in non-Group mode.
-		 * So, if the parser has done its job right, the projected output
-		 * tuple's targetList must not contain any direct references to
-		 * input columns, and so it's a waste of time to create an
-		 * all-nulls input tuple.  We just let the tuple slot get set
-		 * to NULL instead.  The values returned for the aggregates will
-		 * be the initial values of the transition functions.
-		 */
-
-		/*
-		 * Store the representative input tuple (or NULL, if none)
-		 * in the tuple table slot reserved for it.
+		 * Store the representative input tuple in the tuple table slot
+		 * reserved for it.
 		 */
 		ExecStoreTuple(inputTuple,
 					   aggstate->csstate.css_ScanTupleSlot,