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+--
+-- PARALLEL
+--
+
+create function sp_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;
+
+-- Parallel Append with partial-subplans
+explain (costs off)
+  select round(avg(aa)), sum(aa) from a_star;
+select round(avg(aa)), sum(aa) from a_star a1;
+
+-- Parallel Append with both partial and non-partial subplans
+alter table c_star set (parallel_workers = 0);
+alter table d_star set (parallel_workers = 0);
+explain (costs off)
+  select round(avg(aa)), sum(aa) from a_star;
+select round(avg(aa)), sum(aa) from a_star a2;
+
+-- Parallel Append with only non-partial subplans
+alter table a_star set (parallel_workers = 0);
+alter table b_star set (parallel_workers = 0);
+alter table e_star set (parallel_workers = 0);
+alter table f_star set (parallel_workers = 0);
+explain (costs off)
+  select round(avg(aa)), sum(aa) from a_star;
+select round(avg(aa)), sum(aa) from a_star a3;
+
+-- Disable Parallel Append
+alter table a_star reset (parallel_workers);
+alter table b_star reset (parallel_workers);
+alter table c_star reset (parallel_workers);
+alter table d_star reset (parallel_workers);
+alter table e_star reset (parallel_workers);
+alter table f_star reset (parallel_workers);
+set enable_parallel_append to off;
+explain (costs off)
+  select round(avg(aa)), sum(aa) from a_star;
+select round(avg(aa)), sum(aa) from a_star a4;
+reset enable_parallel_append;
+
+-- Parallel Append that runs serially
+create function sp_test_func() returns setof text as
+$$ select 'foo'::varchar union all select 'bar'::varchar $$
+language sql stable;
+select sp_test_func() order by 1;
+
+-- Parallel Append is not to be used when the subpath depends on the outer param
+create table part_pa_test(a int, b int) partition by range(a);
+create table part_pa_test_p1 partition of part_pa_test for values from (minvalue) to (0);
+create table part_pa_test_p2 partition of part_pa_test for values from (0) to (maxvalue);
+explain (costs off)
+	select (select max((select pa1.b from part_pa_test pa1 where pa1.a = pa2.a)))
+	from part_pa_test pa2;
+drop table part_pa_test;
+
+-- test with leader participation disabled
+set parallel_leader_participation = off;
+explain (costs off)
+  select count(*) from tenk1 where stringu1 = 'GRAAAA';
+select count(*) from tenk1 where stringu1 = 'GRAAAA';
+
+-- test with leader participation disabled, but no workers available (so
+-- the leader will have to run the plan despite the setting)
+set max_parallel_workers = 0;
+explain (costs off)
+  select count(*) from tenk1 where stringu1 = 'GRAAAA';
+select count(*) from tenk1 where stringu1 = 'GRAAAA';
+
+reset max_parallel_workers;
+reset parallel_leader_participation;
+
+-- test that parallel_restricted function doesn't run in worker
+alter table tenk1 set (parallel_workers = 4);
+explain (verbose, costs off)
+select sp_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(sp_parallel_restricted(unique1)) from tenk1
+	group by(sp_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 plan for a query containing initplan.
+set enable_indexscan = off;
+set enable_indexonlyscan = off;
+set enable_bitmapscan = off;
+alter table tenk2 set (parallel_workers = 2);
+
+explain (costs off)
+	select count(*) from tenk1
+        where tenk1.unique1 = (Select max(tenk2.unique1) from tenk2);
+select count(*) from tenk1
+    where tenk1.unique1 = (Select max(tenk2.unique1) from tenk2);
+
+reset enable_indexscan;
+reset enable_indexonlyscan;
+reset enable_bitmapscan;
+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;
+
+-- test rescans for a Limit node with a parallel node beneath it.
+reset enable_seqscan;
+set enable_indexonlyscan to off;
+set enable_indexscan to off;
+alter table tenk1 set (parallel_workers = 0);
+alter table tenk2 set (parallel_workers = 1);
+explain (costs off)
+select count(*) from tenk1
+  left join (select tenk2.unique1 from tenk2 order by 1 limit 1000) ss
+  on tenk1.unique1 < ss.unique1 + 1
+  where tenk1.unique1 < 2;
+select count(*) from tenk1
+  left join (select tenk2.unique1 from tenk2 order by 1 limit 1000) ss
+  on tenk1.unique1 < ss.unique1 + 1
+  where tenk1.unique1 < 2;
+--reset the value of workers for each table as it was before this test.
+alter table tenk1 set (parallel_workers = 4);
+alter table tenk2 reset (parallel_workers);
+
+reset enable_material;
+reset enable_bitmapscan;
+reset enable_indexonlyscan;
+reset enable_indexscan;
+
+-- 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;
+
+-- test accumulation of stats for parallel nodes
+reset enable_seqscan;
+alter table tenk2 set (parallel_workers = 0);
+explain (analyze, timing off, summary off, costs off)
+   select count(*) from tenk1, tenk2 where tenk1.hundred > 1
+        and tenk2.thousand=0;
+alter table tenk2 reset (parallel_workers);
+
+reset work_mem;
+create function explain_parallel_sort_stats() returns setof text
+language plpgsql as
+$$
+declare ln text;
+begin
+    for ln in
+        explain (analyze, timing off, summary off, costs off)
+          select * from
+          (select ten from tenk1 where ten < 100 order by ten) ss
+          right join (values (1),(2),(3)) v(x) on true
+    loop
+        ln := regexp_replace(ln, 'Memory: \S*',  'Memory: xxx');
+        return next ln;
+    end loop;
+end;
+$$;
+select * from explain_parallel_sort_stats();
+
+reset enable_indexscan;
+reset enable_hashjoin;
+reset enable_mergejoin;
+reset enable_material;
+reset effective_io_concurrency;
+drop table bmscantest;
+drop function explain_parallel_sort_stats();
+
+-- 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 expressions in targetlist are pushed down for gather merge
+create function sp_simple_func(var1 integer) returns integer
+as $$
+begin
+        return var1 + 10;
+end;
+$$ language plpgsql PARALLEL SAFE;
+
+explain (costs off, verbose)
+    select ten, sp_simple_func(ten) from tenk1 where ten < 100 order by ten;
+
+drop function sp_simple_func(integer);
+
+-- test handling of SRFs in targetlist (bug in 10.0)
+
+explain (costs off)
+   select count(*), generate_series(1,2) from tenk1 group by twenty;
+
+select count(*), generate_series(1,2) from tenk1 group by twenty;
+
+-- test gather merge with parallel leader participation disabled
+set parallel_leader_participation = off;
+
+explain (costs off)
+   select count(*) from tenk1 group by twenty;
+
+select count(*) from tenk1 group by twenty;
+
+reset parallel_leader_participation;
+
+--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;
+
+-- check parallelized int8 aggregate (bug #14897)
+explain (costs off)
+select avg(unique1::int8) from tenk1;
+
+select avg(unique1::int8) from tenk1;
+
+-- 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;
+
+-- gather merge test with 0 workers, with parallel leader
+-- participation disabled (the leader will have to run the plan
+-- despite the setting)
+set parallel_leader_participation = off;
+explain (costs off)
+   select string4 from tenk1 order by string4 limit 5;
+select string4 from tenk1 order by string4 limit 5;
+
+reset parallel_leader_participation;
+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 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;
+
+-- Window function calculation can't be pushed to workers.
+explain (costs off, verbose)
+  select count(*) from tenk1 a where (unique1, two) in
+    (select unique1, row_number() over() from tenk1 b);
+
+
+-- LIMIT/OFFSET within sub-selects can't be pushed to workers.
+explain (costs off)
+  select * from tenk1 a where two in
+    (select two from tenk1 b where stringu1 like '%AAAA' limit 3);
+
+-- 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
+-- (make the error message long enough to require multiple bufferloads)
+SAVEPOINT settings;
+SET LOCAL force_parallel_mode = 1;
+select (stringu1 || repeat('abcd', 5000))::int2 from tenk1 where unique1 = 1;
+ROLLBACK TO SAVEPOINT settings;
+
+-- test interaction with set-returning functions
+SAVEPOINT settings;
+
+-- multiple subqueries under a single Gather node
+-- must set parallel_setup_cost > 0 to discourage multiple Gather nodes
+SET LOCAL parallel_setup_cost = 10;
+EXPLAIN (COSTS OFF)
+SELECT unique1 FROM tenk1 WHERE fivethous = tenthous + 1
+UNION ALL
+SELECT unique1 FROM tenk1 WHERE fivethous = tenthous + 1;
+ROLLBACK TO SAVEPOINT settings;
+
+-- can't use multiple subqueries under a single Gather node due to initPlans
+EXPLAIN (COSTS OFF)
+SELECT unique1 FROM tenk1 WHERE fivethous =
+	(SELECT unique1 FROM tenk1 WHERE fivethous = 1 LIMIT 1)
+UNION ALL
+SELECT unique1 FROM tenk1 WHERE fivethous =
+	(SELECT unique2 FROM tenk1 WHERE fivethous = 1 LIMIT 1)
+ORDER BY 1;
+
+-- test interaction with SRFs
+SELECT * FROM information_schema.foreign_data_wrapper_options
+ORDER BY 1, 2, 3;
+
+EXPLAIN (VERBOSE, COSTS OFF)
+SELECT generate_series(1, two), array(select generate_series(1, two))
+  FROM tenk1 ORDER BY tenthous;
+
+-- test passing expanded-value representations to workers
+CREATE FUNCTION make_some_array(int,int) returns int[] as
+$$declare x int[];
+  begin
+    x[1] := $1;
+    x[2] := $2;
+    return x;
+  end$$ language plpgsql parallel safe;
+CREATE TABLE fooarr(f1 text, f2 int[], f3 text);
+INSERT INTO fooarr VALUES('1', ARRAY[1,2], 'one');
+
+PREPARE pstmt(text, int[]) AS SELECT * FROM fooarr WHERE f1 = $1 AND f2 = $2;
+EXPLAIN (COSTS OFF) EXECUTE pstmt('1', make_some_array(1,2));
+EXECUTE pstmt('1', make_some_array(1,2));
+DEALLOCATE pstmt;
+
+-- test interaction between subquery and partial_paths
+CREATE VIEW tenk1_vw_sec WITH (security_barrier) AS SELECT * FROM tenk1;
+EXPLAIN (COSTS OFF)
+SELECT 1 FROM tenk1_vw_sec
+  WHERE (SELECT sum(f1) FROM int4_tbl WHERE f1 < unique1) < 100;
+
+rollback;