postgres/src/test/regress/sql/select_parallel.sql

--
-- 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;
select count(*) from a_star;

-- 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;

-- test parallel plan when group by expression is in target list.
explain (costs off)
	select length(stringu1) from tenk1 group by length(stringu1);
select length(stringu1) from tenk1 group by length(stringu1);

explain (costs off)
	select stringu1, count(*) from tenk1 group by stringu1 order by stringu1;

-- 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));

-- test prepared statement
prepare tenk1_count(integer) As select  count((unique1)) from tenk1 where hundred > $1;
explain (costs off) execute tenk1_count(1);
execute tenk1_count(1);
deallocate tenk1_count;

-- 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);
select count(*) from tenk1 where (two, four) not in
	(select hundred, thousand from tenk2 where thousand > 100);
-- this is not parallel-safe due to use of random() within SubLink's testexpr:
explain (costs off)
	select * from tenk1 where (unique1 + random())::integer not in
	(select ten from tenk2);
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;
select  count((unique1)) from tenk1 where hundred > 1;

-- test parallel index-only scans.
explain (costs off)
	select  count(*) from tenk1 where thousand > 95;
select  count(*) from tenk1 where thousand > 95;

-- test rescan cases too
set enable_material = false;

explain (costs off)
select * from
  (select count(unique1) from tenk1 where hundred > 10) ss
  right join (values (1),(2),(3)) v(x) on true;
select * from
  (select count(unique1) from tenk1 where hundred > 10) ss
  right join (values (1),(2),(3)) v(x) on true;

explain (costs off)
select * from
  (select count(*) from tenk1 where thousand > 99) ss
  right join (values (1),(2),(3)) v(x) on true;
select * from
  (select count(*) from tenk1 where thousand > 99) ss
  right join (values (1),(2),(3)) v(x) on true;

reset enable_material;
reset enable_seqscan;
reset enable_bitmapscan;

-- test parallel bitmap heap scan.
set enable_seqscan to off;
set enable_indexscan to off;
set enable_hashjoin to off;
set enable_mergejoin to off;
set enable_material to off;
-- test prefetching, if the platform allows it
DO $$
BEGIN
 SET effective_io_concurrency = 50;
EXCEPTION WHEN invalid_parameter_value THEN
END $$;
set work_mem='64kB';  --set small work mem to force lossy pages
explain (costs off)
	select count(*) from tenk1, tenk2 where tenk1.hundred > 1 and tenk2.thousand=0;
select count(*) from tenk1, tenk2 where tenk1.hundred > 1 and tenk2.thousand=0;

create table bmscantest (a int, t text);
insert into bmscantest select r, 'fooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo' FROM generate_series(1,100000) r;
create index i_bmtest ON bmscantest(a);
select count(*) from bmscantest where a>1;

reset enable_seqscan;
reset enable_indexscan;
reset enable_hashjoin;
reset enable_mergejoin;
reset enable_material;
reset effective_io_concurrency;
reset work_mem;
drop table bmscantest;

-- 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;
select  count(*) from tenk1, tenk2 where tenk1.unique1 = tenk2.unique1;

reset enable_hashjoin;
reset enable_nestloop;

-- test gather merge
set enable_hashagg = false;

explain (costs off)
   select count(*) from tenk1 group by twenty;

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;

reset enable_hashagg;

-- gather merge test with a LIMIT
explain (costs off)
  select fivethous from tenk1 order by fivethous limit 4;

select fivethous from tenk1 order by fivethous limit 4;

-- gather merge test with 0 worker
set max_parallel_workers = 0;
explain (costs off)
   select string4 from tenk1 order by string4 limit 5;
select string4 from tenk1 order by string4 limit 5;
reset max_parallel_workers;

SAVEPOINT settings;
SET LOCAL force_parallel_mode = 1;
explain (costs off)
  select stringu1::int2 from tenk1 where unique1 = 1;
ROLLBACK TO SAVEPOINT settings;

-- exercise record typmod remapping between backends
CREATE OR REPLACE FUNCTION make_record(n int)
  RETURNS RECORD LANGUAGE plpgsql PARALLEL SAFE AS
$$
BEGIN
  RETURN CASE n
           WHEN 1 THEN ROW(1)
           WHEN 2 THEN ROW(1, 2)
           WHEN 3 THEN ROW(1, 2, 3)
           WHEN 4 THEN ROW(1, 2, 3, 4)
           ELSE ROW(1, 2, 3, 4, 5)
         END;
END;
$$;
SAVEPOINT settings;
SET LOCAL force_parallel_mode = 1;
SELECT make_record(x) FROM (SELECT generate_series(1, 5) x) ss ORDER BY x;
ROLLBACK TO SAVEPOINT settings;
DROP function make_record(n int);

-- test the sanity of parallel query after the active role is dropped.
drop role if exists regress_parallel_worker;
create role regress_parallel_worker;
set role regress_parallel_worker;
reset session authorization;
drop role regress_parallel_worker;
set force_parallel_mode = 1;
select count(*) from tenk1;
reset force_parallel_mode;
reset role;

-- to increase the parallel query test coverage
SAVEPOINT settings;
SET LOCAL force_parallel_mode = 1;
EXPLAIN (analyze, timing off, summary off, costs off) SELECT * FROM tenk1;
ROLLBACK TO SAVEPOINT settings;

-- provoke error in worker
SAVEPOINT settings;
SET LOCAL force_parallel_mode = 1;
select stringu1::int2 from tenk1 where unique1 = 1;
ROLLBACK TO SAVEPOINT settings;

rollback;