500
(20 rows)
---test rescan behavior of gather merge
-set enable_material = false;
-explain (costs off)
-select * from
- (select string4, count(unique2)
- from tenk1 group by string4 order by string4) ss
- right join (values (1),(2),(3)) v(x) on true;
- QUERY PLAN
-----------------------------------------------------------
- Nested Loop Left Join
- -> Values Scan on "*VALUES*"
- -> Finalize GroupAggregate
- Group Key: tenk1.string4
- -> Gather Merge
- Workers Planned: 4
- -> Partial GroupAggregate
- Group Key: tenk1.string4
- -> Sort
- Sort Key: tenk1.string4
- -> Parallel Seq Scan on tenk1
-(11 rows)
-
-select * from
- (select string4, count(unique2)
- from tenk1 group by string4 order by string4) ss
- right join (values (1),(2),(3)) v(x) on true;
- string4 | count | x
----------+-------+---
- AAAAxx | 2500 | 1
- HHHHxx | 2500 | 1
- OOOOxx | 2500 | 1
- VVVVxx | 2500 | 1
- AAAAxx | 2500 | 2
- HHHHxx | 2500 | 2
- OOOOxx | 2500 | 2
- VVVVxx | 2500 | 2
- AAAAxx | 2500 | 3
- HHHHxx | 2500 | 3
- OOOOxx | 2500 | 3
- VVVVxx | 2500 | 3
-(12 rows)
-
-reset enable_material;
-- gather merge test with 0 worker
set max_parallel_workers = 0;
explain (costs off)
select count(*) from tenk1 group by twenty;
---test rescan behavior of gather merge
-set enable_material = false;
-
-explain (costs off)
-select * from
- (select string4, count(unique2)
- from tenk1 group by string4 order by string4) ss
- right join (values (1),(2),(3)) v(x) on true;
-
-select * from
- (select string4, count(unique2)
- from tenk1 group by string4 order by string4) ss
- right join (values (1),(2),(3)) v(x) on true;
-
-reset enable_material;
-
-- gather merge test with 0 worker
set max_parallel_workers = 0;
explain (costs off)