postgresql/src/test/regress/expected/tablesample.out

CREATE TABLE test_tablesample (id int, name text) WITH (fillfactor=10);
-- use fillfactor so we don't have to load too much data to get multiple pages
INSERT INTO test_tablesample
  SELECT i, repeat(i::text, 200) FROM generate_series(0, 9) s(i);
SELECT t.id FROM test_tablesample AS t TABLESAMPLE SYSTEM (50) REPEATABLE (0);
 id 
----
  3
  4
  5
  6
  7
  8
(6 rows)

SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (100.0/11) REPEATABLE (0);
 id 
----
(0 rows)

SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (0);
 id 
----
  3
  4
  5
  6
  7
  8
(6 rows)

SELECT id FROM test_tablesample TABLESAMPLE BERNOULLI (50) REPEATABLE (0);
 id 
----
  4
  5
  6
  7
  8
(5 rows)

SELECT id FROM test_tablesample TABLESAMPLE BERNOULLI (5.5) REPEATABLE (0);
 id 
----
  7
(1 row)

-- 100% should give repeatable count results (ie, all rows) in any case
SELECT count(*) FROM test_tablesample TABLESAMPLE SYSTEM (100);
 count 
-------
    10
(1 row)

SELECT count(*) FROM test_tablesample TABLESAMPLE SYSTEM (100) REPEATABLE (1+2);
 count 
-------
    10
(1 row)

SELECT count(*) FROM test_tablesample TABLESAMPLE SYSTEM (100) REPEATABLE (0.4);
 count 
-------
    10
(1 row)

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
                     View "public.test_tablesample_v1"
 Column |  Type   | Collation | Nullable | Default | Storage | Description 
--------+---------+-----------+----------+---------+---------+-------------
 id     | integer |           |          |         | plain   | 
View definition:
 SELECT id
   FROM test_tablesample TABLESAMPLE system ((10 * 2)) REPEATABLE (2);

\d+ test_tablesample_v2
                     View "public.test_tablesample_v2"
 Column |  Type   | Collation | Nullable | Default | Storage | Description 
--------+---------+-----------+----------+---------+---------+-------------
 id     | integer |           |          |         | plain   | 
View definition:
 SELECT id
   FROM test_tablesample TABLESAMPLE system (99);

-- check a sampled query doesn't affect cursor in progress
BEGIN;
DECLARE tablesample_cur SCROLL CURSOR FOR
  SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (0);
FETCH FIRST FROM tablesample_cur;
 id 
----
  3
(1 row)

FETCH NEXT FROM tablesample_cur;
 id 
----
  4
(1 row)

FETCH NEXT FROM tablesample_cur;
 id 
----
  5
(1 row)

SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (0);
 id 
----
  3
  4
  5
  6
  7
  8
(6 rows)

FETCH NEXT FROM tablesample_cur;
 id 
----
  6
(1 row)

FETCH NEXT FROM tablesample_cur;
 id 
----
  7
(1 row)

FETCH NEXT FROM tablesample_cur;
 id 
----
  8
(1 row)

FETCH FIRST FROM tablesample_cur;
 id 
----
  3
(1 row)

FETCH NEXT FROM tablesample_cur;
 id 
----
  4
(1 row)

FETCH NEXT FROM tablesample_cur;
 id 
----
  5
(1 row)

FETCH NEXT FROM tablesample_cur;
 id 
----
  6
(1 row)

FETCH NEXT FROM tablesample_cur;
 id 
----
  7
(1 row)

FETCH NEXT FROM tablesample_cur;
 id 
----
  8
(1 row)

CLOSE tablesample_cur;
END;
EXPLAIN (COSTS OFF)
  SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (2);
                             QUERY PLAN                             
--------------------------------------------------------------------
 Sample Scan on test_tablesample
   Sampling: system ('50'::real) REPEATABLE ('2'::double precision)
(2 rows)

EXPLAIN (COSTS OFF)
  SELECT * FROM test_tablesample_v1;
                             QUERY PLAN                             
--------------------------------------------------------------------
 Sample Scan on test_tablesample
   Sampling: system ('20'::real) REPEATABLE ('2'::double precision)
(2 rows)

-- check inheritance behavior
explain (costs off)
  select count(*) from person tablesample bernoulli (100);
                   QUERY PLAN                    
-------------------------------------------------
 Aggregate
   ->  Append
         ->  Sample Scan on person person_1
               Sampling: bernoulli ('100'::real)
         ->  Sample Scan on emp person_2
               Sampling: bernoulli ('100'::real)
         ->  Sample Scan on student person_3
               Sampling: bernoulli ('100'::real)
         ->  Sample Scan on stud_emp person_4
               Sampling: bernoulli ('100'::real)
(10 rows)

select count(*) from person tablesample bernoulli (100);
 count 
-------
    58
(1 row)

select count(*) from person;
 count 
-------
    58
(1 row)

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

-- check behavior during rescans, as well as correct handling of min/max pct
select * from
  (values (0),(100)) v(pct),
  lateral (select count(*) from tenk1 tablesample bernoulli (pct)) ss;
 pct | count 
-----+-------
   0 |     0
 100 | 10000
(2 rows)

select * from
  (values (0),(100)) v(pct),
  lateral (select count(*) from tenk1 tablesample system (pct)) ss;
 pct | count 
-----+-------
   0 |     0
 100 | 10000
(2 rows)

explain (costs off)
select pct, count(unique1) from
  (values (0),(100)) v(pct),
  lateral (select * from tenk1 tablesample bernoulli (pct)) ss
  group by pct;
                       QUERY PLAN                       
--------------------------------------------------------
 HashAggregate
   Group Key: "*VALUES*".column1
   ->  Nested Loop
         ->  Values Scan on "*VALUES*"
         ->  Sample Scan on tenk1
               Sampling: bernoulli ("*VALUES*".column1)
(6 rows)

select pct, count(unique1) from
  (values (0),(100)) v(pct),
  lateral (select * from tenk1 tablesample bernoulli (pct)) ss
  group by pct;
 pct | count 
-----+-------
 100 | 10000
(1 row)

select pct, count(unique1) from
  (values (0),(100)) v(pct),
  lateral (select * from tenk1 tablesample system (pct)) ss
  group by pct;
 pct | count 
-----+-------
 100 | 10000
(1 row)

-- errors
SELECT id FROM test_tablesample TABLESAMPLE FOOBAR (1);
ERROR:  tablesample method foobar does not exist
LINE 1: SELECT id FROM test_tablesample TABLESAMPLE FOOBAR (1);
                                                    ^
SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (NULL);
ERROR:  TABLESAMPLE parameter cannot be null
SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (NULL);
ERROR:  TABLESAMPLE REPEATABLE parameter cannot be null
SELECT id FROM test_tablesample TABLESAMPLE BERNOULLI (-1);
ERROR:  sample percentage must be between 0 and 100
SELECT id FROM test_tablesample TABLESAMPLE BERNOULLI (200);
ERROR:  sample percentage must be between 0 and 100
SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (-1);
ERROR:  sample percentage must be between 0 and 100
SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (200);
ERROR:  sample percentage must be between 0 and 100
SELECT id FROM test_tablesample_v1 TABLESAMPLE BERNOULLI (1);
ERROR:  TABLESAMPLE clause can only be applied to tables and materialized views
LINE 1: SELECT id FROM test_tablesample_v1 TABLESAMPLE BERNOULLI (1)...
                       ^
INSERT INTO test_tablesample_v1 VALUES(1);
ERROR:  cannot insert into view "test_tablesample_v1"
DETAIL:  Views containing TABLESAMPLE are not automatically updatable.
HINT:  To enable inserting into the view, provide an INSTEAD OF INSERT trigger or an unconditional ON INSERT DO INSTEAD rule.
WITH query_select AS (SELECT * FROM test_tablesample)
SELECT * FROM query_select TABLESAMPLE BERNOULLI (5.5) REPEATABLE (1);
ERROR:  TABLESAMPLE clause can only be applied to tables and materialized views
LINE 2: SELECT * FROM query_select TABLESAMPLE BERNOULLI (5.5) REPEA...
                      ^
SELECT q.* FROM (SELECT * FROM test_tablesample) as q TABLESAMPLE BERNOULLI (5);
ERROR:  syntax error at or near "TABLESAMPLE"
LINE 1: ...CT q.* FROM (SELECT * FROM test_tablesample) as q TABLESAMPL...
                                                             ^
-- 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);
                QUERY PLAN                 
-------------------------------------------
 Append
   ->  Sample Scan on parted_sample_1
         Sampling: bernoulli ('100'::real)
   ->  Sample Scan on parted_sample_2
         Sampling: bernoulli ('100'::real)
(5 rows)

drop table parted_sample, parted_sample_1, parted_sample_2;