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--
-- PARALLEL
--
create or replace function parallel_restricted(int) returns int as
$$begin return $1; end$$ language plpgsql parallel restricted;
-- Serializable isolation would disable parallel query, so explicitly use an
-- arbitrary other level.
begin isolation level repeatable read;
-- encourage use of parallel plans
set parallel_setup_cost=0;
set parallel_tuple_cost=0;
set min_parallel_table_scan_size=0;
set max_parallel_workers_per_gather=4;
explain (costs off)
select count(*) from a_star;
QUERY PLAN
-----------------------------------------------------
Finalize Aggregate
-> Gather
Workers Planned: 1
-> Partial Aggregate
-> Append
-> Parallel Seq Scan on a_star
-> Parallel Seq Scan on b_star
-> Parallel Seq Scan on c_star
-> Parallel Seq Scan on d_star
-> Parallel Seq Scan on e_star
-> Parallel Seq Scan on f_star
(11 rows)
select count(*) from a_star;
count
-------
50
(1 row)
-- test that parallel_restricted function doesn't run in worker
alter table tenk1 set (parallel_workers = 4);
explain (verbose, costs off)
select parallel_restricted(unique1) from tenk1
where stringu1 = 'GRAAAA' order by 1;
QUERY PLAN
---------------------------------------------------------
Sort
Output: (parallel_restricted(unique1))
Sort Key: (parallel_restricted(tenk1.unique1))
-> Gather
Output: parallel_restricted(unique1)
Workers Planned: 4
-> Parallel Seq Scan on public.tenk1
Output: unique1
Filter: (tenk1.stringu1 = 'GRAAAA'::name)
(9 rows)
-- test parallel plan when group by expression is in target list.
explain (costs off)
select length(stringu1) from tenk1 group by length(stringu1);
QUERY PLAN
---------------------------------------------------
Finalize HashAggregate
Group Key: (length((stringu1)::text))
-> Gather
Workers Planned: 4
-> Partial HashAggregate
Group Key: length((stringu1)::text)
-> Parallel Seq Scan on tenk1
(7 rows)
select length(stringu1) from tenk1 group by length(stringu1);
length
--------
6
(1 row)
explain (costs off)
select stringu1, count(*) from tenk1 group by stringu1 order by stringu1;
QUERY PLAN
----------------------------------------------------
Sort
Sort Key: stringu1
-> Finalize HashAggregate
Group Key: stringu1
-> Gather
Workers Planned: 4
-> Partial HashAggregate
Group Key: stringu1
-> Parallel Seq Scan on tenk1
(9 rows)
-- test that parallel plan for aggregates is not selected when
-- target list contains parallel restricted clause.
explain (costs off)
select sum(parallel_restricted(unique1)) from tenk1
group by(parallel_restricted(unique1));
QUERY PLAN
-------------------------------------------------------------------
HashAggregate
Group Key: parallel_restricted(unique1)
-> Gather
Workers Planned: 4
-> Parallel Index Only Scan using tenk1_unique1 on tenk1
(5 rows)
-- test parallel plans for queries containing un-correlated subplans.
alter table tenk2 set (parallel_workers = 0);
explain (costs off)
select count(*) from tenk1 where (two, four) not in
(select hundred, thousand from tenk2 where thousand > 100);
QUERY PLAN
------------------------------------------------------
Finalize Aggregate
-> Gather
Workers Planned: 4
-> Partial Aggregate
-> Parallel Seq Scan on tenk1
Filter: (NOT (hashed SubPlan 1))
SubPlan 1
-> Seq Scan on tenk2
Filter: (thousand > 100)
(9 rows)
select count(*) from tenk1 where (two, four) not in
(select hundred, thousand from tenk2 where thousand > 100);
count
-------
10000
(1 row)
alter table tenk2 reset (parallel_workers);
-- test parallel index scans.
set enable_seqscan to off;
set enable_bitmapscan to off;
explain (costs off)
select count((unique1)) from tenk1 where hundred > 1;
QUERY PLAN
--------------------------------------------------------------------
Finalize Aggregate
-> Gather
Workers Planned: 4
-> Partial Aggregate
-> Parallel Index Scan using tenk1_hundred on tenk1
Index Cond: (hundred > 1)
(6 rows)
select count((unique1)) from tenk1 where hundred > 1;
count
-------
9800
(1 row)
-- test parallel index-only scans.
explain (costs off)
select count(*) from tenk1 where thousand > 95;
QUERY PLAN
--------------------------------------------------------------------------------
Finalize Aggregate
-> Gather
Workers Planned: 4
-> Partial Aggregate
-> Parallel Index Only Scan using tenk1_thous_tenthous on tenk1
Index Cond: (thousand > 95)
(6 rows)
select count(*) from tenk1 where thousand > 95;
count
-------
9040
(1 row)
reset enable_seqscan;
reset enable_bitmapscan;
-- test parallel bitmap heap scan.
set enable_seqscan to off;
set enable_indexscan to off;
explain (costs off)
select count((unique1)) from tenk1 where hundred > 1;
QUERY PLAN
------------------------------------------------------------
Finalize Aggregate
-> Gather
Workers Planned: 4
-> Partial Aggregate
-> Parallel Bitmap Heap Scan on tenk1
Recheck Cond: (hundred > 1)
-> Bitmap Index Scan on tenk1_hundred
Index Cond: (hundred > 1)
(8 rows)
reset enable_seqscan;
reset enable_indexscan;
-- test parallel merge join path.
set enable_hashjoin to off;
set enable_nestloop to off;
explain (costs off)
select count(*) from tenk1, tenk2 where tenk1.unique1 = tenk2.unique1;
QUERY PLAN
-------------------------------------------------------------------------------
Finalize Aggregate
-> Gather
Workers Planned: 4
-> Partial Aggregate
-> Merge Join
Merge Cond: (tenk1.unique1 = tenk2.unique1)
-> Parallel Index Only Scan using tenk1_unique1 on tenk1
-> Index Only Scan using tenk2_unique1 on tenk2
(8 rows)
select count(*) from tenk1, tenk2 where tenk1.unique1 = tenk2.unique1;
count
-------
10000
(1 row)
reset enable_hashjoin;
reset enable_nestloop;
set force_parallel_mode=1;
explain (costs off)
select stringu1::int2 from tenk1 where unique1 = 1;
QUERY PLAN
-----------------------------------------------
Gather
Workers Planned: 1
Single Copy: true
-> Index Scan using tenk1_unique1 on tenk1
Index Cond: (unique1 = 1)
(5 rows)
-- provoke error in worker
select stringu1::int2 from tenk1 where unique1 = 1;
ERROR: invalid input syntax for integer: "BAAAAA"
CONTEXT: parallel worker
rollback;
|
