SET client_min_messages TO LOG;
CREATE TABLE s1.tl (a int);
INSERT INTO s1.tl (SELECT a FROM generate_series(0, 100000) a);
--- Queries on ordinary tables
+-- Queries on ordinary tables with default setting
EXPLAIN (COSTS false) SELECT * FROM s1.t1;
QUERY PLAN
----------------
SET parallel_setup_cost to 0;
SET parallel_tuple_cost to 0;
SET min_parallel_relation_size to 0;
+SET max_parallel_workers_per_gather to DEFAULT;
/*+Parallel(t1 10)*/
EXPLAIN (COSTS false) SELECT * FROM s1.t1;
LOG: pg_hint_plan:
-> Parallel Seq Scan on t1
(3 rows)
-SET parallel_setup_cost to DEFAULT;
-SET parallel_tuple_cost to DEFAULT;
-SET min_parallel_relation_size to DEFAULT;
/*+Parallel(t1 10 hard)*/
EXPLAIN (COSTS false) SELECT * FROM s1.t1;
LOG: pg_hint_plan:
-> Parallel Seq Scan on p1_c3_c2
(12 rows)
--- hinting on children don't work but enables parallel
+-- hinting on children makes the whole inheritance parallel
/*+Parallel(p1_c1 10 hard)*/
EXPLAIN (COSTS false) SELECT * FROM p1;
LOG: pg_hint_plan:
used hint:
-not used hint:
Parallel(p1_c1 10 hard)
+not used hint:
duplication hint:
error hint:
QUERY PLAN
-------------------------------------------
Gather
- Workers Planned: 1
+ Workers Planned: 10
-> Append
-> Parallel Seq Scan on p1
-> Parallel Seq Scan on p1_c1
(12 rows)
-- Joins
-EXPLAIN (COSTS false) SELECT * FROM p1_c1 join p2_c1 on p1_c1.id = p2_c1.id;
- QUERY PLAN
-----------------------------------------
+EXPLAIN (COSTS false) SELECT * FROM p1_c1_c1 join p2_c1_c1 on p1_c1_c1.id = p2_c1_c1.id;
+ QUERY PLAN
+------------------------------------------
Hash Join
- Hash Cond: (p1_c1.id = p2_c1.id)
- -> Append
- -> Seq Scan on p1_c1
- -> Seq Scan on p1_c1_c1
- -> Seq Scan on p1_c1_c2
+ Hash Cond: (p1_c1_c1.id = p2_c1_c1.id)
+ -> Seq Scan on p1_c1_c1
-> Hash
- -> Append
- -> Seq Scan on p2_c1
- -> Seq Scan on p2_c1_c1
- -> Seq Scan on p2_c1_c2
-(11 rows)
+ -> Seq Scan on p2_c1_c1
+(5 rows)
-/*+Parallel(p1_c1 10 hard)*/
-EXPLAIN (COSTS false) SELECT * FROM p1_c1 join p2_c1 on p1_c1.id = p2_c1.id;
+/*+Parallel(p1_c1_c1 10 hard)*/
+EXPLAIN (COSTS false) SELECT * FROM p1_c1_c1 join p2_c1_c1 on p1_c1_c1.id = p2_c1_c1.id;
LOG: pg_hint_plan:
used hint:
-Parallel(p1_c1 10 hard)
+Parallel(p1_c1_c1 10 hard)
not used hint:
duplication hint:
error hint:
- QUERY PLAN
--------------------------------------------------------
+ QUERY PLAN
+-------------------------------------------------
Hash Join
- Hash Cond: (p1_c1.id = p2_c1.id)
- -> Gather
- Workers Planned: 10
- -> Append
- -> Parallel Seq Scan on p1_c1
- -> Parallel Seq Scan on p1_c1_c1
- -> Parallel Seq Scan on p1_c1_c2
+ Hash Cond: (p2_c1_c1.id = p1_c1_c1.id)
+ -> Seq Scan on p2_c1_c1
-> Hash
-> Gather
- Workers Planned: 1
- -> Append
- -> Parallel Seq Scan on p2_c1
- -> Parallel Seq Scan on p2_c1_c1
- -> Parallel Seq Scan on p2_c1_c2
-(15 rows)
+ Workers Planned: 10
+ -> Parallel Seq Scan on p1_c1_c1
+(7 rows)
-/*+Parallel(p2_c1 10 hard)*/
-EXPLAIN (COSTS false) SELECT * FROM p1_c1 join p2_c1 on p1_c1.id = p2_c1.id;
+SET parallel_setup_cost to 0;
+SET parallel_tuple_cost to 0;
+SET min_parallel_relation_size to 0;
+/*+Parallel(p1_c1_c1 10 soft) Parallel(p2_c1_c1 0)*/
+EXPLAIN (COSTS false) SELECT * FROM p1_c1_c1 join p2_c1_c1 on p1_c1_c1.id = p2_c1_c1.id;
LOG: pg_hint_plan:
used hint:
-Parallel(p2_c1 10 hard)
+Parallel(p1_c1_c1 10 soft)
+Parallel(p2_c1_c1 0 soft)
not used hint:
duplication hint:
error hint:
- QUERY PLAN
--------------------------------------------------------
- Hash Join
- Hash Cond: (p1_c1.id = p2_c1.id)
- -> Gather
- Workers Planned: 1
- -> Append
- -> Parallel Seq Scan on p1_c1
- -> Parallel Seq Scan on p1_c1_c1
- -> Parallel Seq Scan on p1_c1_c2
- -> Hash
- -> Gather
- Workers Planned: 10
- -> Append
- -> Parallel Seq Scan on p2_c1
- -> Parallel Seq Scan on p2_c1_c1
- -> Parallel Seq Scan on p2_c1_c2
-(15 rows)
+ QUERY PLAN
+------------------------------------------------
+ Gather
+ Workers Planned: 1
+ -> Hash Join
+ Hash Cond: (p1_c1_c1.id = p2_c1_c1.id)
+ -> Parallel Seq Scan on p1_c1_c1
+ -> Hash
+ -> Seq Scan on p2_c1_c1
+(7 rows)
-/*+Parallel(p1_c1 10 hard) Parallel(p2_c1 10 hard)*/
-EXPLAIN (COSTS false) SELECT * FROM p1_c1 join p2_c1 on p1_c1.id = p2_c1.id;
+/*+Parallel(p1_c1_c1 10 hard) Parallel(p2_c1_c1 0)*/
+EXPLAIN (COSTS false) SELECT * FROM p1_c1_c1 join p2_c1_c1 on p1_c1_c1.id = p2_c1_c1.id;
LOG: pg_hint_plan:
used hint:
-Parallel(p1_c1 10 hard)
-Parallel(p2_c1 10 hard)
+Parallel(p1_c1_c1 10 hard)
+Parallel(p2_c1_c1 0 soft)
not used hint:
duplication hint:
error hint:
- QUERY PLAN
--------------------------------------------------------
+ QUERY PLAN
+------------------------------------------------
+ Gather
+ Workers Planned: 10
+ -> Hash Join
+ Hash Cond: (p1_c1_c1.id = p2_c1_c1.id)
+ -> Parallel Seq Scan on p1_c1_c1
+ -> Hash
+ -> Seq Scan on p2_c1_c1
+(7 rows)
+
+/*+Parallel(p1_c1_c1 10 hard) Parallel(p2_c1_c1 10 hard)*/
+EXPLAIN (COSTS false) SELECT * FROM p1_c1_c1 join p2_c1_c1 on p1_c1_c1.id = p2_c1_c1.id;
+LOG: pg_hint_plan:
+used hint:
+Parallel(p1_c1_c1 10 hard)
+Parallel(p2_c1_c1 10 hard)
+not used hint:
+duplication hint:
+error hint:
+
+ QUERY PLAN
+-------------------------------------------------
Hash Join
- Hash Cond: (p1_c1.id = p2_c1.id)
+ Hash Cond: (p1_c1_c1.id = p2_c1_c1.id)
-> Gather
Workers Planned: 10
- -> Append
- -> Parallel Seq Scan on p1_c1
- -> Parallel Seq Scan on p1_c1_c1
- -> Parallel Seq Scan on p1_c1_c2
+ -> Parallel Seq Scan on p1_c1_c1
-> Hash
-> Gather
Workers Planned: 10
- -> Append
- -> Parallel Seq Scan on p2_c1
- -> Parallel Seq Scan on p2_c1_c1
- -> Parallel Seq Scan on p2_c1_c2
-(15 rows)
+ -> Parallel Seq Scan on p2_c1_c1
+(9 rows)
-- Joins on inheritance tables
SET parallel_setup_cost to 0;
-> Parallel Seq Scan on p2_c3_c2
(27 rows)
+/*+Parallel(p1 10)Parallel(p2 0)*/
+EXPLAIN (COSTS false) SELECT * FROM p1 join p2 on p1.id = p2.id;
+LOG: pg_hint_plan:
+used hint:
+Parallel(p1 10 soft)
+Parallel(p2 0 soft)
+not used hint:
+duplication hint:
+error hint:
+
+ QUERY PLAN
+-------------------------------------------------
+ Gather
+ Workers Planned: 1
+ -> Hash Join
+ Hash Cond: (p1.id = p2.id)
+ -> Append
+ -> Parallel Seq Scan on p1
+ -> Parallel Seq Scan on p1_c1
+ -> Parallel Seq Scan on p1_c2
+ -> Parallel Seq Scan on p1_c3
+ -> Parallel Seq Scan on p1_c4
+ -> Parallel Seq Scan on p1_c1_c1
+ -> Parallel Seq Scan on p1_c1_c2
+ -> Parallel Seq Scan on p1_c3_c1
+ -> Parallel Seq Scan on p1_c3_c2
+ -> Hash
+ -> Append
+ -> Seq Scan on p2
+ -> Seq Scan on p2_c1
+ -> Seq Scan on p2_c2
+ -> Seq Scan on p2_c3
+ -> Seq Scan on p2_c4
+ -> Seq Scan on p2_c1_c1
+ -> Seq Scan on p2_c1_c2
+ -> Seq Scan on p2_c3_c1
+ -> Seq Scan on p2_c3_c2
+(25 rows)
+
SET parallel_setup_cost to DEFAULT;
SET parallel_tuple_cost to DEFAULT;
SET min_parallel_relation_size to DEFAULT;
-> Parallel Seq Scan on p2_c3_c2
(27 rows)
--- parallelism is not available for the case
+-- parallel overrides index scan
/*+Parallel(p1 10 hard) IndexScan(p1) */
EXPLAIN (COSTS false) SELECT * FROM p1 join p2 on p1.id = p2.id;
LOG: pg_hint_plan:
-> Parallel Seq Scan on p2_c3_c2
(27 rows)
+/*+Parallel(p1 0 hard) IndexScan(p1) */
+EXPLAIN (COSTS false) SELECT * FROM p1 join p2 on p1.id = p2.id;
+LOG: pg_hint_plan:
+used hint:
+IndexScan(p1)
+Parallel(p1 0 hard)
+not used hint:
+duplication hint:
+error hint:
+
+ QUERY PLAN
+--------------------------------------------------------
+ Hash Join
+ Hash Cond: (p1.id = p2.id)
+ -> Append
+ -> Index Scan using p1_pkey on p1
+ -> Index Scan using p1_c1_pkey on p1_c1
+ -> Index Scan using p1_c2_pkey on p1_c2
+ -> Index Scan using p1_c3_pkey on p1_c3
+ -> Index Scan using p1_c4_pkey on p1_c4
+ -> Index Scan using p1_c1_c1_pkey on p1_c1_c1
+ -> Index Scan using p1_c1_c2_pkey on p1_c1_c2
+ -> Index Scan using p1_c3_c1_pkey on p1_c3_c1
+ -> Index Scan using p1_c3_c2_pkey on p1_c3_c2
+ -> Hash
+ -> Append
+ -> Seq Scan on p2
+ -> Seq Scan on p2_c1
+ -> Seq Scan on p2_c2
+ -> Seq Scan on p2_c3
+ -> Seq Scan on p2_c4
+ -> Seq Scan on p2_c1_c1
+ -> Seq Scan on p2_c1_c2
+ -> Seq Scan on p2_c3_c1
+ -> Seq Scan on p2_c3_c2
+(23 rows)
+
-- Parallel on UNION
EXPLAIN (COSTS false) SELECT id FROM p1 UNION ALL SELECT id FROM p2;
QUERY PLAN
-> Seq Scan on p2_c3_c2
(19 rows)
--- some of the scans are not parallel, so this cannot be parallel
+-- parallel hinting on any relation enables parallel
SET parallel_setup_cost to 0;
SET parallel_tuple_cost to 0;
SET min_parallel_relation_size to 0;
-> Parallel Seq Scan on p2_c3_c2
(21 rows)
--- all children are parallel, so this can be parallel
-/*+Parallel(p1 10) Parallel(p2 10) */
+-- set hint also does
+/*+Set(max_parallel_workers_per_gather 1)*/
EXPLAIN (COSTS false) SELECT id FROM p1 UNION ALL SELECT id FROM p2;
LOG: pg_hint_plan:
used hint:
-Parallel(p1 10 soft)
-Parallel(p2 10 soft)
+Set(max_parallel_workers_per_gather 1)
not used hint:
duplication hint:
error hint:
-> Parallel Seq Scan on p2_c3_c2
(21 rows)
+-- applies largest number of workers on merged parallel paths
SET parallel_setup_cost to DEFAULT;
SET parallel_tuple_cost to DEFAULT;
SET min_parallel_relation_size to DEFAULT;
-SET max_parallel_workers_per_gather to DEFAULT;
-/*+Parallel(p1 10 hard)Parallel(p2 10 hard) */
+SET max_parallel_workers_per_gather to 10;
+/*+Parallel(p1 5 hard)Parallel(p2 6 hard) */
EXPLAIN (COSTS false) SELECT id FROM p1 UNION ALL SELECT id FROM p2;
LOG: pg_hint_plan:
used hint:
-Parallel(p1 10 hard)
-Parallel(p2 10 hard)
+Parallel(p1 5 hard)
+Parallel(p2 6 hard)
not used hint:
duplication hint:
error hint:
QUERY PLAN
-------------------------------------------
Gather
- Workers Planned: 10
+ Workers Planned: 6
-> Append
-> Parallel Seq Scan on p1
-> Parallel Seq Scan on p1_c1