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|
--
-- 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;
two | unique1 | unique2 | stringu1
-----+---------+---------+----------
| 51 | 76 | ZBAAAA
| 52 | 985 | ACAAAA
(2 rows)
SELECT ''::text AS five, unique1, unique2, stringu1
FROM onek WHERE unique1 > 60
ORDER BY unique1 LIMIT 5;
five | unique1 | unique2 | stringu1
------+---------+---------+----------
| 61 | 560 | JCAAAA
| 62 | 633 | KCAAAA
| 63 | 296 | LCAAAA
| 64 | 479 | MCAAAA
| 65 | 64 | NCAAAA
(5 rows)
SELECT ''::text AS two, unique1, unique2, stringu1
FROM onek WHERE unique1 > 60 AND unique1 < 63
ORDER BY unique1 LIMIT 5;
two | unique1 | unique2 | stringu1
-----+---------+---------+----------
| 61 | 560 | JCAAAA
| 62 | 633 | KCAAAA
(2 rows)
SELECT ''::text AS three, unique1, unique2, stringu1
FROM onek WHERE unique1 > 100
ORDER BY unique1 LIMIT 3 OFFSET 20;
three | unique1 | unique2 | stringu1
-------+---------+---------+----------
| 121 | 700 | REAAAA
| 122 | 519 | SEAAAA
| 123 | 777 | TEAAAA
(3 rows)
SELECT ''::text AS zero, unique1, unique2, stringu1
FROM onek WHERE unique1 < 50
ORDER BY unique1 DESC LIMIT 8 OFFSET 99;
zero | unique1 | unique2 | stringu1
------+---------+---------+----------
(0 rows)
SELECT ''::text AS eleven, unique1, unique2, stringu1
FROM onek WHERE unique1 < 50
ORDER BY unique1 DESC LIMIT 20 OFFSET 39;
eleven | unique1 | unique2 | stringu1
--------+---------+---------+----------
| 10 | 520 | KAAAAA
| 9 | 49 | JAAAAA
| 8 | 653 | IAAAAA
| 7 | 647 | HAAAAA
| 6 | 978 | GAAAAA
| 5 | 541 | FAAAAA
| 4 | 833 | EAAAAA
| 3 | 431 | DAAAAA
| 2 | 326 | CAAAAA
| 1 | 214 | BAAAAA
| 0 | 998 | AAAAAA
(11 rows)
SELECT ''::text AS ten, unique1, unique2, stringu1
FROM onek
ORDER BY unique1 OFFSET 990;
ten | unique1 | unique2 | stringu1
-----+---------+---------+----------
| 990 | 369 | CMAAAA
| 991 | 426 | DMAAAA
| 992 | 363 | EMAAAA
| 993 | 661 | FMAAAA
| 994 | 695 | GMAAAA
| 995 | 144 | HMAAAA
| 996 | 258 | IMAAAA
| 997 | 21 | JMAAAA
| 998 | 549 | KMAAAA
| 999 | 152 | LMAAAA
(10 rows)
SELECT ''::text AS five, unique1, unique2, stringu1
FROM onek
ORDER BY unique1 OFFSET 990 LIMIT 5;
five | unique1 | unique2 | stringu1
------+---------+---------+----------
| 990 | 369 | CMAAAA
| 991 | 426 | DMAAAA
| 992 | 363 | EMAAAA
| 993 | 661 | FMAAAA
| 994 | 695 | GMAAAA
(5 rows)
SELECT ''::text AS five, unique1, unique2, stringu1
FROM onek
ORDER BY unique1 LIMIT 5 OFFSET 900;
five | unique1 | unique2 | stringu1
------+---------+---------+----------
| 900 | 913 | QIAAAA
| 901 | 931 | RIAAAA
| 902 | 702 | SIAAAA
| 903 | 641 | TIAAAA
| 904 | 793 | UIAAAA
(5 rows)
-- Test null limit and offset. The planner would discard a simple null
-- constant, so to ensure executor is exercised, do this:
select * from int8_tbl limit (case when random() < 0.5 then null::bigint end);
q1 | q2
------------------+-------------------
123 | 456
123 | 4567890123456789
4567890123456789 | 123
4567890123456789 | 4567890123456789
4567890123456789 | -4567890123456789
(5 rows)
select * from int8_tbl offset (case when random() < 0.5 then null::bigint end);
q1 | q2
------------------+-------------------
123 | 456
123 | 4567890123456789
4567890123456789 | 123
4567890123456789 | 4567890123456789
4567890123456789 | -4567890123456789
(5 rows)
-- Test assorted cases involving backwards fetch from a LIMIT plan node
begin;
rollback;
select sum(tenthous) as s1, sum(tenthous) + random()*0 as s2
from tenk1 group by thousand order by thousand limit 3;
s1 | s2
-------+-------
45000 | 45000
45010 | 45010
45020 | 45020
(3 rows)
SELECT thousand
FROM onek WHERE thousand < 5
ORDER BY thousand FETCH FIRST 2 ROW ONLY;
thousand
----------
0
0
(2 rows)
-- SKIP LOCKED and WITH TIES are incompatible
SELECT thousand
FROM onek WHERE thousand < 5
ORDER BY thousand FETCH FIRST 1 ROW WITH TIES FOR UPDATE SKIP LOCKED;
ERROR: SKIP LOCKED and WITH TIES options cannot be used together
-- should fail
SELECT ''::text AS two, unique1, unique2, stringu1
FROM onek WHERE unique1 > 50
FETCH FIRST 2 ROW WITH TIES;
ERROR: WITH TIES cannot be specified without ORDER BY clause
-- leave these views
|
