src/test/singlenode_regress/sql/tablesample.sql

CREATE TABLE test_tablesample (dist int, id int, name text) WITH (fillfactor=10);
-- use fillfactor so we don't have to load too much data to get multiple pages

-- Changed the column length in order to match the expected results based on relation's blocksz
INSERT INTO test_tablesample SELECT 0, i, repeat(i::text, 875) FROM generate_series(0, 9) s(i) ORDER BY i;
INSERT INTO test_tablesample SELECT 3, i, repeat(i::text, 875) FROM generate_series(10, 19) s(i) ORDER BY i;
INSERT INTO test_tablesample SELECT 5, i, repeat(i::text, 875) FROM generate_series(20, 29) s(i) ORDER BY i;

-- Verify that each segment has the same amount of rows;
SELECT gp_segment_id, count(dist) FROM test_tablesample GROUP BY 1 ORDER BY 1;

SELECT t.id FROM test_tablesample AS t TABLESAMPLE SYSTEM (50) REPEATABLE (0);
SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (100.0/11) REPEATABLE (0);
SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (0);
SELECT id FROM test_tablesample TABLESAMPLE BERNOULLI (50) REPEATABLE (0);
SELECT id FROM test_tablesample TABLESAMPLE BERNOULLI (5.5) REPEATABLE (0);

-- 100% should give repeatable count results (ie, all rows) in any case
SELECT count(*) FROM test_tablesample TABLESAMPLE SYSTEM (100);
SELECT count(*) FROM test_tablesample TABLESAMPLE SYSTEM (100) REPEATABLE (1+2);
SELECT count(*) FROM test_tablesample TABLESAMPLE SYSTEM (100) REPEATABLE (0.4);

CREATE VIEW test_tablesample_v1 AS
  SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (10*2) REPEATABLE (2);
CREATE VIEW test_tablesample_v2 AS
  SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (99);
\d+ test_tablesample_v1
\d+ test_tablesample_v2

-- check a sampled query doesn't affect cursor in progress
BEGIN;
DECLARE tablesample_cur CURSOR FOR
  SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (0) ORDER BY id;

FETCH FIRST FROM tablesample_cur;
FETCH NEXT FROM tablesample_cur;
FETCH NEXT FROM tablesample_cur;

SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (0);

FETCH NEXT FROM tablesample_cur;
FETCH NEXT FROM tablesample_cur;
FETCH NEXT FROM tablesample_cur;

-- Cloudberry: Going backwards on cursors is not supported. By closing the
-- cursor and starting again we pass the tests and keep the file closer to
-- upstream. We do test the rescan methods of tablesample afterwards.
CLOSE tablesample_cur;
DECLARE tablesample_cur CURSOR FOR SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (0) ORDER BY id;
FETCH FIRST FROM tablesample_cur;
FETCH NEXT FROM tablesample_cur;
FETCH NEXT FROM tablesample_cur;
FETCH NEXT FROM tablesample_cur;
FETCH NEXT FROM tablesample_cur;
FETCH NEXT FROM tablesample_cur;

CLOSE tablesample_cur;
END;

EXPLAIN (COSTS OFF)
  SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (2);
EXPLAIN (COSTS OFF)
  SELECT * FROM test_tablesample_v1;

-- check inheritance behavior
explain (costs off)
  select count(*) from person tablesample bernoulli (100);
select count(*) from person tablesample bernoulli (100);
select count(*) from person;

-- check that collations get assigned within the tablesample arguments
SELECT count(*) FROM test_tablesample TABLESAMPLE bernoulli (('1'::text < '0'::text)::int);

-- Cloudberry: Test rescan paths by forcing a nested loop
CREATE TABLE ttr1 (a int, b int);
CREATE TABLE ttr2 (a int, b int);
INSERT INTO ttr1 VALUES (1, 1), (12, 1), (31, 1), (NULL, NULL);
INSERT INTO ttr2 VALUES (1, 2), (12, 2), (31, 2), (NULL, 6);
ANALYZE ttr1;
ANALYZE ttr2;
SET enable_hashjoin TO OFF;
SET enable_mergejoin TO OFF;
SET enable_nestloop TO ON;

EXPLAIN (COSTS OFF) SELECT * FROM ttr1 TABLESAMPLE BERNOULLI (50) REPEATABLE (1), ttr2 TABLESAMPLE BERNOULLI (50) REPEATABLE (1) WHERE ttr1.a = ttr2.a;
SELECT * FROM ttr1 TABLESAMPLE BERNOULLI (50) REPEATABLE (1), ttr2 TABLESAMPLE BERNOULLI (50) REPEATABLE (1) WHERE ttr1.a = ttr2.a;
EXPLAIN (COSTS OFF) SELECT * FROM ttr1 TABLESAMPLE SYSTEM (50) REPEATABLE (1), ttr2 TABLESAMPLE SYSTEM (50) REPEATABLE (1) WHERE ttr1.a = ttr2.a;
SELECT * FROM ttr1 TABLESAMPLE SYSTEM (50) REPEATABLE (1), ttr2 TABLESAMPLE SYSTEM (50) REPEATABLE (1) WHERE ttr1.a = ttr2.a;

RESET enable_hashjoin;
RESET enable_mergejoin;
RESET enable_nestloop;

-- check behavior during rescans, as well as correct handling of min/max pct
-- Cloudberry: does not support laterals completely, rescan specific tests above
-- start_ignore
select * from
  (values (0),(100)) v(pct),
  lateral (select count(*) from tenk1 tablesample bernoulli (pct)) ss;
select * from
  (values (0),(100)) v(pct),
  lateral (select count(*) from tenk1 tablesample system (pct)) ss;
explain (costs off)
select pct, count(unique1) from
  (values (0),(100)) v(pct),
  lateral (select * from tenk1 tablesample bernoulli (pct)) ss
  group by pct;
select pct, count(unique1) from
  (values (0),(100)) v(pct),
  lateral (select * from tenk1 tablesample bernoulli (pct)) ss
  group by pct;
select pct, count(unique1) from
  (values (0),(100)) v(pct),
  lateral (select * from tenk1 tablesample system (pct)) ss
  group by pct;
-- end_ignore

-- Cloudberry: we do have to test min/max pct tests though
select 0 as pct, count(*) from tenk1 tablesample bernoulli (0)
union all
select 100 as pct, count(*) from tenk1 tablesample bernoulli (100);

select 0 as pct, count(*) from tenk1 tablesample system (0)
union all
select 100 as pct, count(*) from tenk1 tablesample system (100);

select 0 as pct, count(unique1) from tenk1 tablesample bernoulli (0)
union all
select 100 as pct, count(unique1) from tenk1 tablesample bernoulli (100);

select 0 as pct, count(unique1) from tenk1 tablesample system (0)
union all
select 100 as pct, count(unique1) from tenk1 tablesample system (100);

-- errors
SELECT id FROM test_tablesample TABLESAMPLE FOOBAR (1);

SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (NULL);
SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (NULL);

SELECT id FROM test_tablesample TABLESAMPLE BERNOULLI (-1);
SELECT id FROM test_tablesample TABLESAMPLE BERNOULLI (200);
SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (-1);
SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (200);

SELECT id FROM test_tablesample_v1 TABLESAMPLE BERNOULLI (1);
INSERT INTO test_tablesample_v1 VALUES(1);

WITH query_select AS (SELECT * FROM test_tablesample)
SELECT * FROM query_select TABLESAMPLE BERNOULLI (5.5) REPEATABLE (1);

SELECT q.* FROM (SELECT * FROM test_tablesample) as q TABLESAMPLE BERNOULLI (5);

-- check partitioned tables support tablesample
create table parted_sample (a int) partition by list (a);
create table parted_sample_1 partition of parted_sample for values in (1);
create table parted_sample_2 partition of parted_sample for values in (2);
explain (costs off)
  select * from parted_sample tablesample bernoulli (100);
drop table parted_sample, parted_sample_1, parted_sample_2;