add_tuplesort_getdatum_nocopy_function.patch

diff --git a/src/backend/executor/nodeAgg.c b/src/backend/executor/nodeAgg.c
index fe74e49814..b5f63b5a2b 100644
--- a/src/backend/executor/nodeAgg.c
+++ b/src/backend/executor/nodeAgg.c
@@ -878,8 +878,8 @@ process_ordered_aggregate_single(AggState *aggstate,
 	 * pfree them when they are no longer needed.
 	 */
 
-	while (tuplesort_getdatum(pertrans->sortstates[aggstate->current_set],
-							  true, newVal, isNull, &newAbbrevVal))
+	while (tuplesort_getdatum_nocopy(pertrans->sortstates[aggstate->current_set],
+									 true, newVal, isNull, &newAbbrevVal))
 	{
 		/*
 		 * Clear and select the working context for evaluation of the equality
@@ -900,24 +900,33 @@ process_ordered_aggregate_single(AggState *aggstate,
 											 pertrans->aggCollation,
 											 oldVal, *newVal)))))
 		{
-			/* equal to prior, so forget this one */
-			if (!pertrans->inputtypeByVal && !*isNull)
-				pfree(DatumGetPointer(*newVal));
+			MemoryContextSwitchTo(oldContext);
+			continue;
 		}
 		else
 		{
 			advance_transition_function(aggstate, pertrans, pergroupstate);
-			/* forget the old value, if any */
-			if (!oldIsNull && !pertrans->inputtypeByVal)
-				pfree(DatumGetPointer(oldVal));
-			/* and remember the new one for subsequent equality checks */
-			oldVal = *newVal;
+
+			MemoryContextSwitchTo(oldContext);
+
+			/*
+			 * Forget the old value, if any and remember the new one for
+			 * subsequent equality checks.
+			 */
+			if (!pertrans->inputtypeByVal)
+			{
+				if (!oldIsNull)
+					pfree(DatumGetPointer(oldVal));
+				if (!*isNull)
+					oldVal = datumCopy(*newVal, pertrans->inputtypeByVal,
+									   pertrans->inputtypeLen);
+			}
+			else
+				oldVal = *newVal;
 			oldAbbrevVal = newAbbrevVal;
 			oldIsNull = *isNull;
 			haveOldVal = true;
 		}
-
-		MemoryContextSwitchTo(oldContext);
 	}
 
 	if (!oldIsNull && !pertrans->inputtypeByVal)
diff --git a/src/backend/executor/nodeSort.c b/src/backend/executor/nodeSort.c
index 37ad35704b..f418be30a1 100644
--- a/src/backend/executor/nodeSort.c
+++ b/src/backend/executor/nodeSort.c
@@ -197,8 +197,8 @@ ExecSort(PlanState *pstate)
 	if (node->datumSort)
 	{
 		ExecClearTuple(slot);
-		if (tuplesort_getdatum(tuplesortstate, ScanDirectionIsForward(dir),
-							   &(slot->tts_values[0]), &(slot->tts_isnull[0]), NULL))
+		if (tuplesort_getdatum_nocopy(tuplesortstate, ScanDirectionIsForward(dir),
+									  &(slot->tts_values[0]), &(slot->tts_isnull[0]), NULL))
 			ExecStoreVirtualTuple(slot);
 	}
 	else
@@ -278,10 +278,10 @@ ExecInitSort(Sort *node, EState *estate, int eflags)
 	outerTupDesc = ExecGetResultType(outerPlanState(sortstate));
 
 	/*
-	 * We perform a Datum sort when we're sorting just a single byval column,
+	 * We perform a Datum sort when we're sorting just a single column,
 	 * otherwise we perform a tuple sort.
 	 */
-	if (outerTupDesc->natts == 1 && TupleDescAttr(outerTupDesc, 0)->attbyval)
+	if (outerTupDesc->natts == 1)
 		sortstate->datumSort = true;
 	else
 		sortstate->datumSort = false;
diff --git a/src/backend/utils/sort/tuplesortvariants.c b/src/backend/utils/sort/tuplesortvariants.c
index afa5bdbf04..a9d51234e6 100644
--- a/src/backend/utils/sort/tuplesortvariants.c
+++ b/src/backend/utils/sort/tuplesortvariants.c
@@ -886,6 +886,58 @@ tuplesort_getdatum(Tuplesortstate *state, bool forward,
 	return true;
 }
 
+/*
+ * Fetch the next Datum in either forward or back direction.
+ * Returns false if no more datums.
+ *
+ * If the Datum is pass-by-ref type, the returned value is a pointer directly
+ * into the tuplesort's stup.tuple.  This is only safe for callers that no
+ * longer require a reference to the datum beyond any subsequent manipulation
+ * of the tuplesort's state.
+ *
+ * Caller may optionally be passed back abbreviated value (on true return
+ * value) when abbreviation was used, which can be used to cheaply avoid
+ * equality checks that might otherwise be required.  Caller can safely make a
+ * determination of "non-equal tuple" based on simple binary inequality.  A
+ * NULL value will have a zeroed abbreviated value representation, which caller
+ * may rely on in abbreviated inequality check.
+ */
+bool
+tuplesort_getdatum_nocopy(Tuplesortstate *state, bool forward,
+						  Datum *val, bool *isNull, Datum *abbrev)
+{
+	TuplesortPublic *base = TuplesortstateGetPublic(state);
+	MemoryContext oldcontext = MemoryContextSwitchTo(base->sortcontext);
+	SortTuple	stup;
+
+	if (!tuplesort_gettuple_common(state, forward, &stup))
+	{
+		MemoryContextSwitchTo(oldcontext);
+		return false;
+	}
+
+	/* Ensure we copy into caller's memory context */
+	MemoryContextSwitchTo(oldcontext);
+
+	/* Record abbreviated key for caller */
+	if (base->sortKeys->abbrev_converter && abbrev)
+		*abbrev = stup.datum1;
+
+	if (stup.isnull1 || !base->tuples)
+	{
+		*val = stup.datum1;
+		*isNull = stup.isnull1;
+	}
+	else
+	{
+		/* use stup.tuple because stup.datum1 may be an abbreviation */
+		*val = PointerGetDatum(stup.tuple);
+		*isNull = false;
+	}
+
+	return true;
+}
+
 
 /*
  * Routines specialized for HeapTuple (actually MinimalTuple) case
diff --git a/src/include/utils/tuplesort.h b/src/include/utils/tuplesort.h
index 4441274990..fc8fc780eb 100644
--- a/src/include/utils/tuplesort.h
+++ b/src/include/utils/tuplesort.h
@@ -441,6 +441,7 @@ extern HeapTuple tuplesort_getheaptuple(Tuplesortstate *state, bool forward);
 extern IndexTuple tuplesort_getindextuple(Tuplesortstate *state, bool forward);
 extern bool tuplesort_getdatum(Tuplesortstate *state, bool forward,
 							   Datum *val, bool *isNull, Datum *abbrev);
-
+extern bool tuplesort_getdatum_nocopy(Tuplesortstate *state, bool forward,
+									  Datum *val, bool *isNull, Datum *abbrev);
 
 #endif							/* TUPLESORT_H */