3 files changed, 23 insertions, 1 deletions
diff --git a/src/backend/utils/sort/tuplesort.c b/src/backend/utils/sort/tuplesort.c
index b17347b2141..9f1df874389 100644
--- a/src/backend/utils/sort/tuplesort.c
+++ b/src/backend/utils/sort/tuplesort.c
@@ -975,6 +975,7 @@ tuplesort_begin_cluster(TupleDesc tupDesc,
 {
 	Tuplesortstate *state = tuplesort_begin_common(workMem, coordinate,
 												   randomAccess);
+	AttrNumber	leading;
 	BTScanInsert indexScanKey;
 	MemoryContext oldcontext;
 	int			i;
@@ -1007,6 +1008,7 @@ tuplesort_begin_cluster(TupleDesc tupDesc,
 	state->abbrevNext = 10;
 
 	state->indexInfo = BuildIndexInfo(indexRel);
+	leading = state->indexInfo->ii_IndexAttrNumbers[0];
 
 	state->tupDesc = tupDesc;	/* assume we need not copy tupDesc */
 
@@ -1045,7 +1047,7 @@ 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 && leading != 0);
 
 		AssertState(sortKey->ssup_attno != 0);
 
diff --git a/src/test/regress/expected/cluster.out b/src/test/regress/expected/cluster.out
index e46a66952f0..7293c0f03ea 100644
--- a/src/test/regress/expected/cluster.out
+++ b/src/test/regress/expected/cluster.out
@@ -511,6 +511,13 @@ 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';
@@ -545,6 +552,13 @@ 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';
diff --git a/src/test/regress/sql/cluster.sql b/src/test/regress/sql/cluster.sql
index aee9cf83e04..99ee533c8d0 100644
--- a/src/test/regress/sql/cluster.sql
+++ b/src/test/regress/sql/cluster.sql
@@ -245,6 +245,9 @@ 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';
@@ -255,6 +258,9 @@ 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';