Fix #7787

citusdata · Dec 16, 2024 · 2d74cf5 · 2d74cf5
1 parent 0355b12
commit 2d74cf5
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diff --git a/src/backend/distributed/planner/query_pushdown_planning.c b/src/backend/distributed/planner/query_pushdown_planning.c
@@ -2049,6 +2049,17 @@ CreateSubqueryTargetListAndAdjustVars(List *columnList)
 		 */
 		column->varno = 1;
 		column->varattno = resNo;
+
+		/*
+		 * With Postgres 16+, we need to ensure that column's varnullingrels - the set
+		 * of join rels that can null the var - is empty. This is because there is one
+		 * one range table entry in the query being constructed by subquery pushdown
+		 * so a non-empty varnullingrels would be incorrect, and confuse the Postgres
+		 * planner as in #7787.
+		 */
+#if PG_VERSION_NUM >= PG_VERSION_16
+		column->varnullingrels = NULL;
+#endif
 	}
 
 	return subqueryTargetEntryList;

diff --git a/src/test/regress/expected/issue_7705.out b/src/test/regress/expected/issue_7705.out
@@ -241,6 +241,88 @@ ORDER BY t1.id;
                                        Output: t1.id
 (22 rows)
 
+-- Issue #7787
+SELECT COUNT(DISTINCT a2)
+FROM t1 LEFT OUTER JOIN t2 ON t1.id = t2.account_id;
+ count
+---------------------------------------------------------------------
+     2
+(1 row)
+
+EXPLAIN (VERBOSE, COSTS OFF, TIMING OFF)
+SELECT COUNT(DISTINCT a2)
+FROM t1 LEFT OUTER JOIN t2 ON t1.id = t2.account_id;
+                                                                                                                            QUERY PLAN
+---------------------------------------------------------------------
+ Aggregate
+   Output: count(DISTINCT remote_scan.count)
+   ->  Sort
+         Output: remote_scan.count
+         Sort Key: remote_scan.count
+         ->  Custom Scan (Citus Adaptive)
+               Output: remote_scan.count
+               Task Count: 4
+               Tasks Shown: One of 4
+               ->  Task
+                     Query: SELECT worker_column_1 AS count FROM (SELECT t2.a2 AS worker_column_1 FROM (issue_7705.t1_30070000 t1 LEFT JOIN issue_7705.t2_30070004 t2 ON ((t1.id OPERATOR(pg_catalog.=) t2.account_id)))) worker_subquery GROUP BY worker_column_1
+                     Node: host=localhost port=xxxxx dbname=regression
+                     ->  HashAggregate
+                           Output: t2.a2
+                           Group Key: t2.a2
+                           ->  Hash Right Join
+                                 Output: t2.a2
+                                 Inner Unique: true
+                                 Hash Cond: (t2.account_id = t1.id)
+                                 ->  Seq Scan on issue_7705.t2_30070004 t2
+                                       Output: t2.id, t2.account_id, t2.a2
+                                 ->  Hash
+                                       Output: t1.id
+                                       ->  Seq Scan on issue_7705.t1_30070000 t1
+                                             Output: t1.id
+(25 rows)
+
+SELECT 1
+FROM t1 LEFT OUTER JOIN t2 ON t1.id = t2.account_id
+HAVING COUNT(DISTINCT a2) > 1;
+ ?column?
+---------------------------------------------------------------------
+        1
+(1 row)
+
+EXPLAIN (VERBOSE, COSTS OFF, TIMING OFF)
+SELECT 1
+FROM t1 LEFT OUTER JOIN t2 ON t1.id = t2.account_id
+HAVING COUNT(DISTINCT a2) > 1;
+                                                                                                                                   QUERY PLAN
+---------------------------------------------------------------------
+ Aggregate
+   Output: remote_scan."?column?"
+   Filter: (count(DISTINCT remote_scan.worker_column_2) > 1)
+   ->  Sort
+         Output: remote_scan."?column?", remote_scan.worker_column_2
+         Sort Key: remote_scan.worker_column_2
+         ->  Custom Scan (Citus Adaptive)
+               Output: remote_scan."?column?", remote_scan.worker_column_2
+               Task Count: 4
+               Tasks Shown: One of 4
+               ->  Task
+                     Query: SELECT 1, worker_column_1 AS worker_column_2 FROM (SELECT t2.a2 AS worker_column_1 FROM (issue_7705.t1_30070000 t1 LEFT JOIN issue_7705.t2_30070004 t2 ON ((t1.id OPERATOR(pg_catalog.=) t2.account_id)))) worker_subquery GROUP BY worker_column_1
+                     Node: host=localhost port=xxxxx dbname=regression
+                     ->  HashAggregate
+                           Output: 1, t2.a2
+                           Group Key: t2.a2
+                           ->  Hash Right Join
+                                 Output: t2.a2
+                                 Inner Unique: true
+                                 Hash Cond: (t2.account_id = t1.id)
+                                 ->  Seq Scan on issue_7705.t2_30070004 t2
+                                       Output: t2.id, t2.account_id, t2.a2
+                                 ->  Hash
+                                       Output: t1.id
+                                       ->  Seq Scan on issue_7705.t1_30070000 t1
+                                             Output: t1.id
+(26 rows)
+
 --- cleanup
 \set VERBOSITY TERSE
 DROP SCHEMA issue_7705 CASCADE;

diff --git a/src/test/regress/sql/issue_7705.sql b/src/test/regress/sql/issue_7705.sql
@@ -66,6 +66,23 @@ SELECT t1.id, CASE nextval('test_seq') %2 = 0 WHEN true THEN t2.a2 ELSE 1 END
 FROM t1 LEFT OUTER JOIN t2 ON t1.id = t2.account_id
 ORDER BY t1.id;
 
+
+-- Issue #7787
+
+SELECT COUNT(DISTINCT a2)
+FROM t1 LEFT OUTER JOIN t2 ON t1.id = t2.account_id;
+EXPLAIN (VERBOSE, COSTS OFF, TIMING OFF)
+SELECT COUNT(DISTINCT a2)
+FROM t1 LEFT OUTER JOIN t2 ON t1.id = t2.account_id;
+
+SELECT 1
+FROM t1 LEFT OUTER JOIN t2 ON t1.id = t2.account_id
+HAVING COUNT(DISTINCT a2) > 1;
+EXPLAIN (VERBOSE, COSTS OFF, TIMING OFF)
+SELECT 1
+FROM t1 LEFT OUTER JOIN t2 ON t1.id = t2.account_id
+HAVING COUNT(DISTINCT a2) > 1;
+
 --- cleanup
 \set VERBOSITY TERSE
 DROP SCHEMA issue_7705 CASCADE;