3 files changed, 65 insertions, 1 deletions
diff --git a/src/backend/executor/nodeHash.c b/src/backend/executor/nodeHash.c
index 2e13ed17e16..5fd1c5553ba 100644
--- a/src/backend/executor/nodeHash.c
+++ b/src/backend/executor/nodeHash.c
@@ -1724,6 +1724,7 @@ retry:
 		/* Store the hash value in the HashJoinTuple header. */
 		hashTuple->hashvalue = hashvalue;
 		memcpy(HJTUPLE_MINTUPLE(hashTuple), tuple, tuple->t_len);
+		HeapTupleHeaderClearMatch(HJTUPLE_MINTUPLE(hashTuple));
 
 		/* Push it onto the front of the bucket's list */
 		ExecParallelHashPushTuple(&hashtable->buckets.shared[bucketno],
diff --git a/src/test/regress/expected/join_hash.out b/src/test/regress/expected/join_hash.out
index 09376514bbd..e892e7cccbf 100644
--- a/src/test/regress/expected/join_hash.out
+++ b/src/test/regress/expected/join_hash.out
@@ -955,6 +955,43 @@ $$);
 (1 row)
 
 rollback to settings;
+-- Hash join reuses the HOT status bit to indicate match status. This can only
+-- be guaranteed to produce correct results if all the hash join tuple match
+-- bits are reset before reuse. This is done upon loading them into the
+-- hashtable.
+SAVEPOINT settings;
+SET enable_parallel_hash = on;
+SET min_parallel_table_scan_size = 0;
+SET parallel_setup_cost = 0;
+SET parallel_tuple_cost = 0;
+CREATE TABLE hjtest_matchbits_t1(id int);
+CREATE TABLE hjtest_matchbits_t2(id int);
+INSERT INTO hjtest_matchbits_t1 VALUES (1);
+INSERT INTO hjtest_matchbits_t2 VALUES (2);
+-- Update should create a HOT tuple. If this status bit isn't cleared, we won't
+-- correctly emit the NULL-extended unmatching tuple in full hash join.
+UPDATE hjtest_matchbits_t2 set id = 2;
+SELECT * FROM hjtest_matchbits_t1 t1 FULL JOIN hjtest_matchbits_t2 t2 ON t1.id = t2.id;
+ id | id 
+----+----
+  1 |   
+    |  2
+(2 rows)
+
+-- Test serial full hash join.
+-- Resetting parallel_setup_cost should force a serial plan.
+-- Just to be safe, however, set enable_parallel_hash to off, as parallel full
+-- hash joins are only supported with shared hashtables.
+RESET parallel_setup_cost;
+SET enable_parallel_hash = off;
+SELECT * FROM hjtest_matchbits_t1 t1 FULL JOIN hjtest_matchbits_t2 t2 ON t1.id = t2.id;
+ id | id 
+----+----
+  1 |   
+    |  2
+(2 rows)
+
+ROLLBACK TO settings;
 rollback;
 -- Verify that hash key expressions reference the correct
 -- nodes. Hashjoin's hashkeys need to reference its outer plan, Hash's
diff --git a/src/test/regress/sql/join_hash.sql b/src/test/regress/sql/join_hash.sql
index 179e94941ca..06bab7a4c78 100644
--- a/src/test/regress/sql/join_hash.sql
+++ b/src/test/regress/sql/join_hash.sql
@@ -506,8 +506,34 @@ $$
 $$);
 rollback to settings;
 
-rollback;
 
+-- Hash join reuses the HOT status bit to indicate match status. This can only
+-- be guaranteed to produce correct results if all the hash join tuple match
+-- bits are reset before reuse. This is done upon loading them into the
+-- hashtable.
+SAVEPOINT settings;
+SET enable_parallel_hash = on;
+SET min_parallel_table_scan_size = 0;
+SET parallel_setup_cost = 0;
+SET parallel_tuple_cost = 0;
+CREATE TABLE hjtest_matchbits_t1(id int);
+CREATE TABLE hjtest_matchbits_t2(id int);
+INSERT INTO hjtest_matchbits_t1 VALUES (1);
+INSERT INTO hjtest_matchbits_t2 VALUES (2);
+-- Update should create a HOT tuple. If this status bit isn't cleared, we won't
+-- correctly emit the NULL-extended unmatching tuple in full hash join.
+UPDATE hjtest_matchbits_t2 set id = 2;
+SELECT * FROM hjtest_matchbits_t1 t1 FULL JOIN hjtest_matchbits_t2 t2 ON t1.id = t2.id;
+-- Test serial full hash join.
+-- Resetting parallel_setup_cost should force a serial plan.
+-- Just to be safe, however, set enable_parallel_hash to off, as parallel full
+-- hash joins are only supported with shared hashtables.
+RESET parallel_setup_cost;
+SET enable_parallel_hash = off;
+SELECT * FROM hjtest_matchbits_t1 t1 FULL JOIN hjtest_matchbits_t2 t2 ON t1.id = t2.id;
+ROLLBACK TO settings;
+
+rollback;
 
 -- Verify that hash key expressions reference the correct
 -- nodes. Hashjoin's hashkeys need to reference its outer plan, Hash's