postgres
diff --git a/‎src/backend/utils/sort/tuplesort.c
Lines changed: 4 additions & 4 deletions b/‎src/backend/utils/sort/tuplesort.c
Lines changed: 4 additions & 4 deletions
diff --git a/‎src/test/regress/expected/cluster.out
Lines changed: 14 additions & 0 deletions b/‎src/test/regress/expected/cluster.out
Lines changed: 14 additions & 0 deletions
diff --git a/‎src/test/regress/sql/cluster.sql
Lines changed: 6 additions & 0 deletions b/‎src/test/regress/sql/cluster.sql
Lines changed: 6 additions & 0 deletions
@@ -1051,7 +1051,7 @@ tuplesort_begin_heap(TupleDesc tupDesc,
 		sortKey->ssup_nulls_first = nullsFirstFlags[i];
 		sortKey->ssup_attno = attNums[i];
 		/* Convey if abbreviation optimization is applicable in principle */
-		sortKey->abbreviate = (i == 0);
+		sortKey->abbreviate = (i == 0 && state->haveDatum1);
 
 		PrepareSortSupportFromOrderingOp(sortOperators[i], sortKey);
 	}
@@ -1157,7 +1157,7 @@ tuplesort_begin_cluster(TupleDesc tupDesc,
 			(scanKey->sk_flags & SK_BT_NULLS_FIRST) != 0;
 		sortKey->ssup_attno = scanKey->sk_attno;
 		/* Convey if abbreviation optimization is applicable in principle */
-		sortKey->abbreviate = (i == 0);
+		sortKey->abbreviate = (i == 0 && state->haveDatum1);
 
 		AssertState(sortKey->ssup_attno != 0);
 
@@ -1238,7 +1238,7 @@ tuplesort_begin_index_btree(Relation heapRel,
 			(scanKey->sk_flags & SK_BT_NULLS_FIRST) != 0;
 		sortKey->ssup_attno = scanKey->sk_attno;
 		/* Convey if abbreviation optimization is applicable in principle */
-		sortKey->abbreviate = (i == 0);
+		sortKey->abbreviate = (i == 0 && state->haveDatum1);
 
 		AssertState(sortKey->ssup_attno != 0);
 
@@ -1348,7 +1348,7 @@ tuplesort_begin_index_gist(Relation heapRel,
 		sortKey->ssup_nulls_first = false;
 		sortKey->ssup_attno = i + 1;
 		/* Convey if abbreviation optimization is applicable in principle */
-		sortKey->abbreviate = (i == 0);
+		sortKey->abbreviate = (i == 0 && state->haveDatum1);
 
 		AssertState(sortKey->ssup_attno != 0);
 
 
@@ -577,6 +577,13 @@ SELECT * FROM clstr_expression WHERE -a = -3 ORDER BY -a, b;
 COMMIT;
 -- and after clustering on clstr_expression_minus_a
 CLUSTER clstr_expression USING clstr_expression_minus_a;
+WITH rows AS
+  (SELECT ctid, lag(a) OVER (ORDER BY ctid) AS la, a FROM clstr_expression)
+SELECT * FROM rows WHERE la < a;
+ ctid | la | a 
+------+----+---
+(0 rows)
+
 BEGIN;
 SET LOCAL enable_seqscan = false;
 EXPLAIN (COSTS OFF) SELECT * FROM clstr_expression WHERE upper(b) = 'PREFIX3';
@@ -611,6 +618,13 @@ SELECT * FROM clstr_expression WHERE -a = -3 ORDER BY -a, b;
 COMMIT;
 -- and after clustering on clstr_expression_upper_b
 CLUSTER clstr_expression USING clstr_expression_upper_b;
+WITH rows AS
+  (SELECT ctid, lag(b) OVER (ORDER BY ctid) AS lb, b FROM clstr_expression)
+SELECT * FROM rows WHERE upper(lb) > upper(b);
+ ctid | lb | b 
+------+----+---
+(0 rows)
+
 BEGIN;
 SET LOCAL enable_seqscan = false;
 EXPLAIN (COSTS OFF) SELECT * FROM clstr_expression WHERE upper(b) = 'PREFIX3';
 
@@ -284,6 +284,9 @@ COMMIT;
 
 -- and after clustering on clstr_expression_minus_a
 CLUSTER clstr_expression USING clstr_expression_minus_a;
+WITH rows AS
+  (SELECT ctid, lag(a) OVER (ORDER BY ctid) AS la, a FROM clstr_expression)
+SELECT * FROM rows WHERE la < a;
 BEGIN;
 SET LOCAL enable_seqscan = false;
 EXPLAIN (COSTS OFF) SELECT * FROM clstr_expression WHERE upper(b) = 'PREFIX3';
@@ -294,6 +297,9 @@ COMMIT;
 
 -- and after clustering on clstr_expression_upper_b
 CLUSTER clstr_expression USING clstr_expression_upper_b;
+WITH rows AS
+  (SELECT ctid, lag(b) OVER (ORDER BY ctid) AS lb, b FROM clstr_expression)
+SELECT * FROM rows WHERE upper(lb) > upper(b);
 BEGIN;
 SET LOCAL enable_seqscan = false;
 EXPLAIN (COSTS OFF) SELECT * FROM clstr_expression WHERE upper(b) = 'PREFIX3';