postgresql/src/test/regress/sql/limit.sql

--
-- LIMIT
-- Check the LIMIT/OFFSET feature of SELECT
--

SELECT ''::text AS two, unique1, unique2, stringu1
		FROM onek WHERE unique1 > 50
		ORDER BY unique1 LIMIT 2;
SELECT ''::text AS five, unique1, unique2, stringu1
		FROM onek WHERE unique1 > 60
		ORDER BY unique1 LIMIT 5;
SELECT ''::text AS two, unique1, unique2, stringu1
		FROM onek WHERE unique1 > 60 AND unique1 < 63
		ORDER BY unique1 LIMIT 5;
SELECT ''::text AS three, unique1, unique2, stringu1
		FROM onek WHERE unique1 > 100
		ORDER BY unique1 LIMIT 3 OFFSET 20;
SELECT ''::text AS zero, unique1, unique2, stringu1
		FROM onek WHERE unique1 < 50
		ORDER BY unique1 DESC LIMIT 8 OFFSET 99;
SELECT ''::text AS eleven, unique1, unique2, stringu1
		FROM onek WHERE unique1 < 50
		ORDER BY unique1 DESC LIMIT 20 OFFSET 39;
SELECT ''::text AS ten, unique1, unique2, stringu1
		FROM onek
		ORDER BY unique1 OFFSET 990;
SELECT ''::text AS five, unique1, unique2, stringu1
		FROM onek
		ORDER BY unique1 OFFSET 990 LIMIT 5;
SELECT ''::text AS five, unique1, unique2, stringu1
		FROM onek
		ORDER BY unique1 LIMIT 5 OFFSET 900;

-- Stress test for variable LIMIT in conjunction with bounded-heap sorting

SELECT
  (SELECT n
     FROM (VALUES (1)) AS x,
          (SELECT n FROM generate_series(1,10) AS n
             ORDER BY n LIMIT 1 OFFSET s-1) AS y) AS z
  FROM generate_series(1,10) AS s;

--
-- Test behavior of volatile and set-returning functions in conjunction
-- with ORDER BY and LIMIT.
--

create temp sequence testseq;

explain (verbose, costs off)
select unique1, unique2, nextval('testseq')
  from tenk1 order by unique2 limit 10;

select unique1, unique2, nextval('testseq')
  from tenk1 order by unique2 limit 10;

select currval('testseq');

explain (verbose, costs off)
select unique1, unique2, nextval('testseq')
  from tenk1 order by tenthous limit 10;

select unique1, unique2, nextval('testseq')
  from tenk1 order by tenthous limit 10;

select currval('testseq');

explain (verbose, costs off)
select unique1, unique2, generate_series(1,10)
  from tenk1 order by unique2 limit 7;

select unique1, unique2, generate_series(1,10)
  from tenk1 order by unique2 limit 7;

explain (verbose, costs off)
select unique1, unique2, generate_series(1,10)
  from tenk1 order by tenthous limit 7;

select unique1, unique2, generate_series(1,10)
  from tenk1 order by tenthous limit 7;