2019-10-24 22:58:40 +02:00
|
|
|
-- only use parallelism when explicitly intending to do so
|
|
|
|
SET max_parallel_maintenance_workers = 0;
|
|
|
|
SET max_parallel_workers = 0;
|
2021-02-24 08:13:17 +01:00
|
|
|
-- A table with contents that, when sorted, triggers abbreviated
|
2019-10-24 22:58:40 +02:00
|
|
|
-- key aborts. One easy way to achieve that is to use uuids that all
|
|
|
|
-- have the same prefix, as abbreviated keys for uuids just use the
|
|
|
|
-- first sizeof(Datum) bytes.
|
2019-12-14 21:01:56 +01:00
|
|
|
CREATE TEMP TABLE abbrev_abort_uuids (
|
2019-10-24 22:58:40 +02:00
|
|
|
id serial not null,
|
|
|
|
abort_increasing uuid,
|
|
|
|
abort_decreasing uuid,
|
|
|
|
noabort_increasing uuid,
|
|
|
|
noabort_decreasing uuid);
|
|
|
|
INSERT INTO abbrev_abort_uuids (abort_increasing, abort_decreasing, noabort_increasing, noabort_decreasing)
|
|
|
|
SELECT
|
|
|
|
('00000000-0000-0000-0000-'||to_char(g.i, '000000000000FM'))::uuid abort_increasing,
|
|
|
|
('00000000-0000-0000-0000-'||to_char(20000 - g.i, '000000000000FM'))::uuid abort_decreasing,
|
|
|
|
(to_char(g.i % 10009, '00000000FM')||'-0000-0000-0000-'||to_char(g.i, '000000000000FM'))::uuid noabort_increasing,
|
|
|
|
(to_char(((20000 - g.i) % 10009), '00000000FM')||'-0000-0000-0000-'||to_char(20000 - g.i, '000000000000FM'))::uuid noabort_decreasing
|
|
|
|
FROM generate_series(0, 20000, 1) g(i);
|
|
|
|
-- and a few NULLs
|
|
|
|
INSERT INTO abbrev_abort_uuids(id) VALUES(0);
|
|
|
|
INSERT INTO abbrev_abort_uuids DEFAULT VALUES;
|
|
|
|
INSERT INTO abbrev_abort_uuids DEFAULT VALUES;
|
|
|
|
-- add just a few duplicates
|
|
|
|
INSERT INTO abbrev_abort_uuids (abort_increasing, abort_decreasing, noabort_increasing, noabort_decreasing)
|
|
|
|
SELECT abort_increasing, abort_decreasing, noabort_increasing, noabort_decreasing
|
|
|
|
FROM abbrev_abort_uuids
|
|
|
|
WHERE (id < 10 OR id > 19990) AND id % 3 = 0 AND abort_increasing is not null;
|
|
|
|
----
|
|
|
|
-- Check sort node uses of tuplesort wrt. abbreviated keys
|
|
|
|
----
|
|
|
|
-- plain sort triggering abbreviated abort
|
|
|
|
SELECT abort_increasing, abort_decreasing FROM abbrev_abort_uuids ORDER BY abort_increasing OFFSET 20000 - 4;
|
|
|
|
abort_increasing | abort_decreasing
|
|
|
|
--------------------------------------+--------------------------------------
|
|
|
|
00000000-0000-0000-0000-000000019992 | 00000000-0000-0000-0000-000000000008
|
|
|
|
00000000-0000-0000-0000-000000019993 | 00000000-0000-0000-0000-000000000007
|
|
|
|
00000000-0000-0000-0000-000000019994 | 00000000-0000-0000-0000-000000000006
|
|
|
|
00000000-0000-0000-0000-000000019994 | 00000000-0000-0000-0000-000000000006
|
|
|
|
00000000-0000-0000-0000-000000019995 | 00000000-0000-0000-0000-000000000005
|
|
|
|
00000000-0000-0000-0000-000000019996 | 00000000-0000-0000-0000-000000000004
|
|
|
|
00000000-0000-0000-0000-000000019997 | 00000000-0000-0000-0000-000000000003
|
|
|
|
00000000-0000-0000-0000-000000019997 | 00000000-0000-0000-0000-000000000003
|
|
|
|
00000000-0000-0000-0000-000000019998 | 00000000-0000-0000-0000-000000000002
|
|
|
|
00000000-0000-0000-0000-000000019999 | 00000000-0000-0000-0000-000000000001
|
|
|
|
00000000-0000-0000-0000-000000020000 | 00000000-0000-0000-0000-000000000000
|
|
|
|
00000000-0000-0000-0000-000000020000 | 00000000-0000-0000-0000-000000000000
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
(15 rows)
|
|
|
|
|
|
|
|
SELECT abort_increasing, abort_decreasing FROM abbrev_abort_uuids ORDER BY abort_decreasing NULLS FIRST OFFSET 20000 - 4;
|
|
|
|
abort_increasing | abort_decreasing
|
|
|
|
--------------------------------------+--------------------------------------
|
|
|
|
00000000-0000-0000-0000-000000000011 | 00000000-0000-0000-0000-000000019989
|
|
|
|
00000000-0000-0000-0000-000000000010 | 00000000-0000-0000-0000-000000019990
|
|
|
|
00000000-0000-0000-0000-000000000009 | 00000000-0000-0000-0000-000000019991
|
|
|
|
00000000-0000-0000-0000-000000000008 | 00000000-0000-0000-0000-000000019992
|
|
|
|
00000000-0000-0000-0000-000000000008 | 00000000-0000-0000-0000-000000019992
|
|
|
|
00000000-0000-0000-0000-000000000007 | 00000000-0000-0000-0000-000000019993
|
|
|
|
00000000-0000-0000-0000-000000000006 | 00000000-0000-0000-0000-000000019994
|
|
|
|
00000000-0000-0000-0000-000000000005 | 00000000-0000-0000-0000-000000019995
|
|
|
|
00000000-0000-0000-0000-000000000005 | 00000000-0000-0000-0000-000000019995
|
|
|
|
00000000-0000-0000-0000-000000000004 | 00000000-0000-0000-0000-000000019996
|
|
|
|
00000000-0000-0000-0000-000000000003 | 00000000-0000-0000-0000-000000019997
|
|
|
|
00000000-0000-0000-0000-000000000002 | 00000000-0000-0000-0000-000000019998
|
|
|
|
00000000-0000-0000-0000-000000000002 | 00000000-0000-0000-0000-000000019998
|
|
|
|
00000000-0000-0000-0000-000000000001 | 00000000-0000-0000-0000-000000019999
|
|
|
|
00000000-0000-0000-0000-000000000000 | 00000000-0000-0000-0000-000000020000
|
|
|
|
(15 rows)
|
|
|
|
|
|
|
|
-- plain sort not triggering abbreviated abort
|
|
|
|
SELECT noabort_increasing, noabort_decreasing FROM abbrev_abort_uuids ORDER BY noabort_increasing OFFSET 20000 - 4;
|
|
|
|
noabort_increasing | noabort_decreasing
|
|
|
|
--------------------------------------+--------------------------------------
|
|
|
|
00009997-0000-0000-0000-000000009997 | 00010003-0000-0000-0000-000000010003
|
|
|
|
00009998-0000-0000-0000-000000009998 | 00010002-0000-0000-0000-000000010002
|
|
|
|
00009999-0000-0000-0000-000000009999 | 00010001-0000-0000-0000-000000010001
|
|
|
|
00010000-0000-0000-0000-000000010000 | 00010000-0000-0000-0000-000000010000
|
|
|
|
00010001-0000-0000-0000-000000010001 | 00009999-0000-0000-0000-000000009999
|
|
|
|
00010002-0000-0000-0000-000000010002 | 00009998-0000-0000-0000-000000009998
|
|
|
|
00010003-0000-0000-0000-000000010003 | 00009997-0000-0000-0000-000000009997
|
|
|
|
00010004-0000-0000-0000-000000010004 | 00009996-0000-0000-0000-000000009996
|
|
|
|
00010005-0000-0000-0000-000000010005 | 00009995-0000-0000-0000-000000009995
|
|
|
|
00010006-0000-0000-0000-000000010006 | 00009994-0000-0000-0000-000000009994
|
|
|
|
00010007-0000-0000-0000-000000010007 | 00009993-0000-0000-0000-000000009993
|
|
|
|
00010008-0000-0000-0000-000000010008 | 00009992-0000-0000-0000-000000009992
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
(15 rows)
|
|
|
|
|
|
|
|
SELECT noabort_increasing, noabort_decreasing FROM abbrev_abort_uuids ORDER BY noabort_decreasing NULLS FIRST OFFSET 20000 - 4;
|
|
|
|
noabort_increasing | noabort_decreasing
|
|
|
|
--------------------------------------+--------------------------------------
|
|
|
|
00010006-0000-0000-0000-000000010006 | 00009994-0000-0000-0000-000000009994
|
|
|
|
00010005-0000-0000-0000-000000010005 | 00009995-0000-0000-0000-000000009995
|
|
|
|
00010004-0000-0000-0000-000000010004 | 00009996-0000-0000-0000-000000009996
|
|
|
|
00010003-0000-0000-0000-000000010003 | 00009997-0000-0000-0000-000000009997
|
|
|
|
00010002-0000-0000-0000-000000010002 | 00009998-0000-0000-0000-000000009998
|
|
|
|
00010001-0000-0000-0000-000000010001 | 00009999-0000-0000-0000-000000009999
|
|
|
|
00010000-0000-0000-0000-000000010000 | 00010000-0000-0000-0000-000000010000
|
|
|
|
00009999-0000-0000-0000-000000009999 | 00010001-0000-0000-0000-000000010001
|
|
|
|
00009998-0000-0000-0000-000000009998 | 00010002-0000-0000-0000-000000010002
|
|
|
|
00009997-0000-0000-0000-000000009997 | 00010003-0000-0000-0000-000000010003
|
|
|
|
00009996-0000-0000-0000-000000009996 | 00010004-0000-0000-0000-000000010004
|
|
|
|
00009995-0000-0000-0000-000000009995 | 00010005-0000-0000-0000-000000010005
|
|
|
|
00009994-0000-0000-0000-000000009994 | 00010006-0000-0000-0000-000000010006
|
|
|
|
00009993-0000-0000-0000-000000009993 | 00010007-0000-0000-0000-000000010007
|
|
|
|
00009992-0000-0000-0000-000000009992 | 00010008-0000-0000-0000-000000010008
|
|
|
|
(15 rows)
|
|
|
|
|
|
|
|
-- bounded sort (disables abbreviated keys)
|
|
|
|
SELECT abort_increasing, noabort_increasing FROM abbrev_abort_uuids ORDER BY abort_increasing LIMIT 5;
|
|
|
|
abort_increasing | noabort_increasing
|
|
|
|
--------------------------------------+--------------------------------------
|
|
|
|
00000000-0000-0000-0000-000000000000 | 00000000-0000-0000-0000-000000000000
|
|
|
|
00000000-0000-0000-0000-000000000001 | 00000001-0000-0000-0000-000000000001
|
|
|
|
00000000-0000-0000-0000-000000000002 | 00000002-0000-0000-0000-000000000002
|
|
|
|
00000000-0000-0000-0000-000000000002 | 00000002-0000-0000-0000-000000000002
|
|
|
|
00000000-0000-0000-0000-000000000003 | 00000003-0000-0000-0000-000000000003
|
|
|
|
(5 rows)
|
|
|
|
|
|
|
|
SELECT abort_increasing, noabort_increasing FROM abbrev_abort_uuids ORDER BY noabort_increasing NULLS FIRST LIMIT 5;
|
|
|
|
abort_increasing | noabort_increasing
|
|
|
|
--------------------------------------+--------------------------------------
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
00000000-0000-0000-0000-000000000000 | 00000000-0000-0000-0000-000000000000
|
|
|
|
00000000-0000-0000-0000-000000010009 | 00000000-0000-0000-0000-000000010009
|
|
|
|
(5 rows)
|
|
|
|
|
|
|
|
----
|
|
|
|
-- Check index creation uses of tuplesort wrt. abbreviated keys
|
|
|
|
----
|
|
|
|
-- index creation using abbreviated keys successfully
|
|
|
|
CREATE INDEX abbrev_abort_uuids__noabort_increasing_idx ON abbrev_abort_uuids (noabort_increasing);
|
|
|
|
CREATE INDEX abbrev_abort_uuids__noabort_decreasing_idx ON abbrev_abort_uuids (noabort_decreasing);
|
|
|
|
-- verify
|
|
|
|
EXPLAIN (COSTS OFF)
|
|
|
|
SELECT id, noabort_increasing, noabort_decreasing FROM abbrev_abort_uuids ORDER BY noabort_increasing LIMIT 5;
|
|
|
|
QUERY PLAN
|
|
|
|
-----------------------------------------------------------------------------------------
|
|
|
|
Limit
|
|
|
|
-> Index Scan using abbrev_abort_uuids__noabort_increasing_idx on abbrev_abort_uuids
|
|
|
|
(2 rows)
|
|
|
|
|
|
|
|
SELECT id, noabort_increasing, noabort_decreasing FROM abbrev_abort_uuids ORDER BY noabort_increasing LIMIT 5;
|
|
|
|
id | noabort_increasing | noabort_decreasing
|
|
|
|
-------+--------------------------------------+--------------------------------------
|
|
|
|
1 | 00000000-0000-0000-0000-000000000000 | 00009991-0000-0000-0000-000000020000
|
|
|
|
10010 | 00000000-0000-0000-0000-000000010009 | 00009991-0000-0000-0000-000000009991
|
|
|
|
2 | 00000001-0000-0000-0000-000000000001 | 00009990-0000-0000-0000-000000019999
|
|
|
|
10011 | 00000001-0000-0000-0000-000000010010 | 00009990-0000-0000-0000-000000009990
|
|
|
|
3 | 00000002-0000-0000-0000-000000000002 | 00009989-0000-0000-0000-000000019998
|
|
|
|
(5 rows)
|
|
|
|
|
|
|
|
EXPLAIN (COSTS OFF)
|
|
|
|
SELECT id, noabort_increasing, noabort_decreasing FROM abbrev_abort_uuids ORDER BY noabort_decreasing LIMIT 5;
|
|
|
|
QUERY PLAN
|
|
|
|
-----------------------------------------------------------------------------------------
|
|
|
|
Limit
|
|
|
|
-> Index Scan using abbrev_abort_uuids__noabort_decreasing_idx on abbrev_abort_uuids
|
|
|
|
(2 rows)
|
|
|
|
|
|
|
|
SELECT id, noabort_increasing, noabort_decreasing FROM abbrev_abort_uuids ORDER BY noabort_decreasing LIMIT 5;
|
|
|
|
id | noabort_increasing | noabort_decreasing
|
|
|
|
-------+--------------------------------------+--------------------------------------
|
|
|
|
20001 | 00009991-0000-0000-0000-000000020000 | 00000000-0000-0000-0000-000000000000
|
|
|
|
20010 | 00009991-0000-0000-0000-000000020000 | 00000000-0000-0000-0000-000000000000
|
|
|
|
9992 | 00009991-0000-0000-0000-000000009991 | 00000000-0000-0000-0000-000000010009
|
|
|
|
20000 | 00009990-0000-0000-0000-000000019999 | 00000001-0000-0000-0000-000000000001
|
|
|
|
9991 | 00009990-0000-0000-0000-000000009990 | 00000001-0000-0000-0000-000000010010
|
|
|
|
(5 rows)
|
|
|
|
|
|
|
|
-- index creation using abbreviated keys, hitting abort
|
|
|
|
CREATE INDEX abbrev_abort_uuids__abort_increasing_idx ON abbrev_abort_uuids (abort_increasing);
|
|
|
|
CREATE INDEX abbrev_abort_uuids__abort_decreasing_idx ON abbrev_abort_uuids (abort_decreasing);
|
|
|
|
-- verify
|
|
|
|
EXPLAIN (COSTS OFF)
|
|
|
|
SELECT id, abort_increasing, abort_decreasing FROM abbrev_abort_uuids ORDER BY abort_increasing LIMIT 5;
|
|
|
|
QUERY PLAN
|
|
|
|
---------------------------------------------------------------------------------------
|
|
|
|
Limit
|
|
|
|
-> Index Scan using abbrev_abort_uuids__abort_increasing_idx on abbrev_abort_uuids
|
|
|
|
(2 rows)
|
|
|
|
|
|
|
|
SELECT id, abort_increasing, abort_decreasing FROM abbrev_abort_uuids ORDER BY abort_increasing LIMIT 5;
|
|
|
|
id | abort_increasing | abort_decreasing
|
|
|
|
-------+--------------------------------------+--------------------------------------
|
|
|
|
1 | 00000000-0000-0000-0000-000000000000 | 00000000-0000-0000-0000-000000020000
|
|
|
|
2 | 00000000-0000-0000-0000-000000000001 | 00000000-0000-0000-0000-000000019999
|
|
|
|
3 | 00000000-0000-0000-0000-000000000002 | 00000000-0000-0000-0000-000000019998
|
|
|
|
20004 | 00000000-0000-0000-0000-000000000002 | 00000000-0000-0000-0000-000000019998
|
|
|
|
4 | 00000000-0000-0000-0000-000000000003 | 00000000-0000-0000-0000-000000019997
|
|
|
|
(5 rows)
|
|
|
|
|
|
|
|
EXPLAIN (COSTS OFF)
|
|
|
|
SELECT id, abort_increasing, abort_decreasing FROM abbrev_abort_uuids ORDER BY abort_decreasing LIMIT 5;
|
|
|
|
QUERY PLAN
|
|
|
|
---------------------------------------------------------------------------------------
|
|
|
|
Limit
|
|
|
|
-> Index Scan using abbrev_abort_uuids__abort_decreasing_idx on abbrev_abort_uuids
|
|
|
|
(2 rows)
|
|
|
|
|
|
|
|
SELECT id, abort_increasing, abort_decreasing FROM abbrev_abort_uuids ORDER BY abort_decreasing LIMIT 5;
|
|
|
|
id | abort_increasing | abort_decreasing
|
|
|
|
-------+--------------------------------------+--------------------------------------
|
|
|
|
20001 | 00000000-0000-0000-0000-000000020000 | 00000000-0000-0000-0000-000000000000
|
|
|
|
20010 | 00000000-0000-0000-0000-000000020000 | 00000000-0000-0000-0000-000000000000
|
|
|
|
20000 | 00000000-0000-0000-0000-000000019999 | 00000000-0000-0000-0000-000000000001
|
|
|
|
19999 | 00000000-0000-0000-0000-000000019998 | 00000000-0000-0000-0000-000000000002
|
|
|
|
19998 | 00000000-0000-0000-0000-000000019997 | 00000000-0000-0000-0000-000000000003
|
|
|
|
(5 rows)
|
|
|
|
|
|
|
|
----
|
|
|
|
-- Check CLUSTER uses of tuplesort wrt. abbreviated keys
|
|
|
|
----
|
|
|
|
-- when aborting, increasing order
|
|
|
|
BEGIN;
|
|
|
|
SET LOCAL enable_indexscan = false;
|
|
|
|
CLUSTER abbrev_abort_uuids USING abbrev_abort_uuids__abort_increasing_idx;
|
|
|
|
-- head
|
|
|
|
SELECT id, abort_increasing, abort_decreasing, noabort_increasing, noabort_decreasing
|
|
|
|
FROM abbrev_abort_uuids
|
|
|
|
ORDER BY ctid LIMIT 5;
|
|
|
|
id | abort_increasing | abort_decreasing | noabort_increasing | noabort_decreasing
|
|
|
|
-------+--------------------------------------+--------------------------------------+--------------------------------------+--------------------------------------
|
|
|
|
1 | 00000000-0000-0000-0000-000000000000 | 00000000-0000-0000-0000-000000020000 | 00000000-0000-0000-0000-000000000000 | 00009991-0000-0000-0000-000000020000
|
|
|
|
2 | 00000000-0000-0000-0000-000000000001 | 00000000-0000-0000-0000-000000019999 | 00000001-0000-0000-0000-000000000001 | 00009990-0000-0000-0000-000000019999
|
|
|
|
3 | 00000000-0000-0000-0000-000000000002 | 00000000-0000-0000-0000-000000019998 | 00000002-0000-0000-0000-000000000002 | 00009989-0000-0000-0000-000000019998
|
|
|
|
20004 | 00000000-0000-0000-0000-000000000002 | 00000000-0000-0000-0000-000000019998 | 00000002-0000-0000-0000-000000000002 | 00009989-0000-0000-0000-000000019998
|
|
|
|
4 | 00000000-0000-0000-0000-000000000003 | 00000000-0000-0000-0000-000000019997 | 00000003-0000-0000-0000-000000000003 | 00009988-0000-0000-0000-000000019997
|
|
|
|
(5 rows)
|
|
|
|
|
|
|
|
-- tail
|
|
|
|
SELECT id, abort_increasing, abort_decreasing, noabort_increasing, noabort_decreasing
|
|
|
|
FROM abbrev_abort_uuids
|
|
|
|
ORDER BY ctid DESC LIMIT 5;
|
|
|
|
id | abort_increasing | abort_decreasing | noabort_increasing | noabort_decreasing
|
|
|
|
-------+--------------------------------------+--------------------------------------+--------------------------------------+--------------------------------------
|
|
|
|
0 | | | |
|
|
|
|
20002 | | | |
|
|
|
|
20003 | | | |
|
|
|
|
20001 | 00000000-0000-0000-0000-000000020000 | 00000000-0000-0000-0000-000000000000 | 00009991-0000-0000-0000-000000020000 | 00000000-0000-0000-0000-000000000000
|
|
|
|
20010 | 00000000-0000-0000-0000-000000020000 | 00000000-0000-0000-0000-000000000000 | 00009991-0000-0000-0000-000000020000 | 00000000-0000-0000-0000-000000000000
|
|
|
|
(5 rows)
|
|
|
|
|
|
|
|
ROLLBACK;
|
|
|
|
-- when aborting, decreasing order
|
|
|
|
BEGIN;
|
|
|
|
SET LOCAL enable_indexscan = false;
|
|
|
|
CLUSTER abbrev_abort_uuids USING abbrev_abort_uuids__abort_decreasing_idx;
|
|
|
|
-- head
|
|
|
|
SELECT id, abort_increasing, abort_decreasing, noabort_increasing, noabort_decreasing
|
|
|
|
FROM abbrev_abort_uuids
|
|
|
|
ORDER BY ctid LIMIT 5;
|
|
|
|
id | abort_increasing | abort_decreasing | noabort_increasing | noabort_decreasing
|
|
|
|
-------+--------------------------------------+--------------------------------------+--------------------------------------+--------------------------------------
|
|
|
|
20010 | 00000000-0000-0000-0000-000000020000 | 00000000-0000-0000-0000-000000000000 | 00009991-0000-0000-0000-000000020000 | 00000000-0000-0000-0000-000000000000
|
|
|
|
20001 | 00000000-0000-0000-0000-000000020000 | 00000000-0000-0000-0000-000000000000 | 00009991-0000-0000-0000-000000020000 | 00000000-0000-0000-0000-000000000000
|
|
|
|
20000 | 00000000-0000-0000-0000-000000019999 | 00000000-0000-0000-0000-000000000001 | 00009990-0000-0000-0000-000000019999 | 00000001-0000-0000-0000-000000000001
|
|
|
|
19999 | 00000000-0000-0000-0000-000000019998 | 00000000-0000-0000-0000-000000000002 | 00009989-0000-0000-0000-000000019998 | 00000002-0000-0000-0000-000000000002
|
|
|
|
20009 | 00000000-0000-0000-0000-000000019997 | 00000000-0000-0000-0000-000000000003 | 00009988-0000-0000-0000-000000019997 | 00000003-0000-0000-0000-000000000003
|
|
|
|
(5 rows)
|
|
|
|
|
|
|
|
-- tail
|
|
|
|
SELECT id, abort_increasing, abort_decreasing, noabort_increasing, noabort_decreasing
|
|
|
|
FROM abbrev_abort_uuids
|
|
|
|
ORDER BY ctid DESC LIMIT 5;
|
|
|
|
id | abort_increasing | abort_decreasing | noabort_increasing | noabort_decreasing
|
|
|
|
-------+--------------------------------------+--------------------------------------+--------------------------------------+--------------------------------------
|
|
|
|
0 | | | |
|
|
|
|
20002 | | | |
|
|
|
|
20003 | | | |
|
|
|
|
1 | 00000000-0000-0000-0000-000000000000 | 00000000-0000-0000-0000-000000020000 | 00000000-0000-0000-0000-000000000000 | 00009991-0000-0000-0000-000000020000
|
|
|
|
2 | 00000000-0000-0000-0000-000000000001 | 00000000-0000-0000-0000-000000019999 | 00000001-0000-0000-0000-000000000001 | 00009990-0000-0000-0000-000000019999
|
|
|
|
(5 rows)
|
|
|
|
|
|
|
|
ROLLBACK;
|
|
|
|
-- when not aborting, increasing order
|
|
|
|
BEGIN;
|
|
|
|
SET LOCAL enable_indexscan = false;
|
|
|
|
CLUSTER abbrev_abort_uuids USING abbrev_abort_uuids__noabort_increasing_idx;
|
|
|
|
-- head
|
|
|
|
SELECT id, abort_increasing, abort_decreasing, noabort_increasing, noabort_decreasing
|
|
|
|
FROM abbrev_abort_uuids
|
|
|
|
ORDER BY ctid LIMIT 5;
|
|
|
|
id | abort_increasing | abort_decreasing | noabort_increasing | noabort_decreasing
|
|
|
|
-------+--------------------------------------+--------------------------------------+--------------------------------------+--------------------------------------
|
|
|
|
1 | 00000000-0000-0000-0000-000000000000 | 00000000-0000-0000-0000-000000020000 | 00000000-0000-0000-0000-000000000000 | 00009991-0000-0000-0000-000000020000
|
|
|
|
10010 | 00000000-0000-0000-0000-000000010009 | 00000000-0000-0000-0000-000000009991 | 00000000-0000-0000-0000-000000010009 | 00009991-0000-0000-0000-000000009991
|
|
|
|
2 | 00000000-0000-0000-0000-000000000001 | 00000000-0000-0000-0000-000000019999 | 00000001-0000-0000-0000-000000000001 | 00009990-0000-0000-0000-000000019999
|
|
|
|
10011 | 00000000-0000-0000-0000-000000010010 | 00000000-0000-0000-0000-000000009990 | 00000001-0000-0000-0000-000000010010 | 00009990-0000-0000-0000-000000009990
|
|
|
|
20004 | 00000000-0000-0000-0000-000000000002 | 00000000-0000-0000-0000-000000019998 | 00000002-0000-0000-0000-000000000002 | 00009989-0000-0000-0000-000000019998
|
|
|
|
(5 rows)
|
|
|
|
|
|
|
|
-- tail
|
|
|
|
SELECT id, abort_increasing, abort_decreasing, noabort_increasing, noabort_decreasing
|
|
|
|
FROM abbrev_abort_uuids
|
|
|
|
ORDER BY ctid DESC LIMIT 5;
|
|
|
|
id | abort_increasing | abort_decreasing | noabort_increasing | noabort_decreasing
|
|
|
|
-------+--------------------------------------+--------------------------------------+--------------------------------------+--------------------------------------
|
|
|
|
0 | | | |
|
|
|
|
20002 | | | |
|
|
|
|
20003 | | | |
|
|
|
|
10009 | 00000000-0000-0000-0000-000000010008 | 00000000-0000-0000-0000-000000009992 | 00010008-0000-0000-0000-000000010008 | 00009992-0000-0000-0000-000000009992
|
|
|
|
10008 | 00000000-0000-0000-0000-000000010007 | 00000000-0000-0000-0000-000000009993 | 00010007-0000-0000-0000-000000010007 | 00009993-0000-0000-0000-000000009993
|
|
|
|
(5 rows)
|
|
|
|
|
|
|
|
ROLLBACK;
|
|
|
|
-- when no aborting, decreasing order
|
|
|
|
BEGIN;
|
|
|
|
SET LOCAL enable_indexscan = false;
|
|
|
|
CLUSTER abbrev_abort_uuids USING abbrev_abort_uuids__noabort_decreasing_idx;
|
|
|
|
-- head
|
|
|
|
SELECT id, abort_increasing, abort_decreasing, noabort_increasing, noabort_decreasing
|
|
|
|
FROM abbrev_abort_uuids
|
|
|
|
ORDER BY ctid LIMIT 5;
|
|
|
|
id | abort_increasing | abort_decreasing | noabort_increasing | noabort_decreasing
|
|
|
|
-------+--------------------------------------+--------------------------------------+--------------------------------------+--------------------------------------
|
|
|
|
20010 | 00000000-0000-0000-0000-000000020000 | 00000000-0000-0000-0000-000000000000 | 00009991-0000-0000-0000-000000020000 | 00000000-0000-0000-0000-000000000000
|
|
|
|
20001 | 00000000-0000-0000-0000-000000020000 | 00000000-0000-0000-0000-000000000000 | 00009991-0000-0000-0000-000000020000 | 00000000-0000-0000-0000-000000000000
|
|
|
|
9992 | 00000000-0000-0000-0000-000000009991 | 00000000-0000-0000-0000-000000010009 | 00009991-0000-0000-0000-000000009991 | 00000000-0000-0000-0000-000000010009
|
|
|
|
20000 | 00000000-0000-0000-0000-000000019999 | 00000000-0000-0000-0000-000000000001 | 00009990-0000-0000-0000-000000019999 | 00000001-0000-0000-0000-000000000001
|
|
|
|
9991 | 00000000-0000-0000-0000-000000009990 | 00000000-0000-0000-0000-000000010010 | 00009990-0000-0000-0000-000000009990 | 00000001-0000-0000-0000-000000010010
|
|
|
|
(5 rows)
|
|
|
|
|
|
|
|
-- tail
|
|
|
|
SELECT id, abort_increasing, abort_decreasing, noabort_increasing, noabort_decreasing
|
|
|
|
FROM abbrev_abort_uuids
|
|
|
|
ORDER BY ctid DESC LIMIT 5;
|
|
|
|
id | abort_increasing | abort_decreasing | noabort_increasing | noabort_decreasing
|
|
|
|
-------+--------------------------------------+--------------------------------------+--------------------------------------+--------------------------------------
|
|
|
|
0 | | | |
|
|
|
|
20003 | | | |
|
|
|
|
20002 | | | |
|
|
|
|
9993 | 00000000-0000-0000-0000-000000009992 | 00000000-0000-0000-0000-000000010008 | 00009992-0000-0000-0000-000000009992 | 00010008-0000-0000-0000-000000010008
|
|
|
|
9994 | 00000000-0000-0000-0000-000000009993 | 00000000-0000-0000-0000-000000010007 | 00009993-0000-0000-0000-000000009993 | 00010007-0000-0000-0000-000000010007
|
|
|
|
(5 rows)
|
|
|
|
|
|
|
|
ROLLBACK;
|
|
|
|
----
|
|
|
|
-- test forward and backward scans for in-memory and disk based tuplesort
|
|
|
|
----
|
|
|
|
-- in-memory
|
|
|
|
BEGIN;
|
|
|
|
SET LOCAL enable_indexscan = false;
|
|
|
|
-- unfortunately can't show analyze output confirming sort method,
|
|
|
|
-- the memory used output wouldn't be stable
|
|
|
|
EXPLAIN (COSTS OFF) DECLARE c SCROLL CURSOR FOR SELECT noabort_decreasing FROM abbrev_abort_uuids ORDER BY noabort_decreasing;
|
|
|
|
QUERY PLAN
|
|
|
|
--------------------------------------
|
|
|
|
Sort
|
|
|
|
Sort Key: noabort_decreasing
|
|
|
|
-> Seq Scan on abbrev_abort_uuids
|
|
|
|
(3 rows)
|
|
|
|
|
|
|
|
DECLARE c SCROLL CURSOR FOR SELECT noabort_decreasing FROM abbrev_abort_uuids ORDER BY noabort_decreasing;
|
|
|
|
-- first and second
|
|
|
|
FETCH NEXT FROM c;
|
|
|
|
noabort_decreasing
|
|
|
|
--------------------------------------
|
|
|
|
00000000-0000-0000-0000-000000000000
|
|
|
|
(1 row)
|
|
|
|
|
|
|
|
FETCH NEXT FROM c;
|
|
|
|
noabort_decreasing
|
|
|
|
--------------------------------------
|
|
|
|
00000000-0000-0000-0000-000000000000
|
|
|
|
(1 row)
|
|
|
|
|
|
|
|
-- scroll beyond beginning
|
|
|
|
FETCH BACKWARD FROM c;
|
|
|
|
noabort_decreasing
|
|
|
|
--------------------------------------
|
|
|
|
00000000-0000-0000-0000-000000000000
|
|
|
|
(1 row)
|
|
|
|
|
|
|
|
FETCH BACKWARD FROM c;
|
|
|
|
noabort_decreasing
|
|
|
|
--------------------
|
|
|
|
(0 rows)
|
|
|
|
|
|
|
|
FETCH BACKWARD FROM c;
|
|
|
|
noabort_decreasing
|
|
|
|
--------------------
|
|
|
|
(0 rows)
|
|
|
|
|
|
|
|
FETCH BACKWARD FROM c;
|
|
|
|
noabort_decreasing
|
|
|
|
--------------------
|
|
|
|
(0 rows)
|
|
|
|
|
|
|
|
FETCH NEXT FROM c;
|
|
|
|
noabort_decreasing
|
|
|
|
--------------------------------------
|
|
|
|
00000000-0000-0000-0000-000000000000
|
|
|
|
(1 row)
|
|
|
|
|
2023-10-09 05:48:47 +02:00
|
|
|
-- scroll beyond end
|
2019-10-24 22:58:40 +02:00
|
|
|
FETCH LAST FROM c;
|
|
|
|
noabort_decreasing
|
|
|
|
--------------------
|
|
|
|
|
|
|
|
(1 row)
|
|
|
|
|
|
|
|
FETCH BACKWARD FROM c;
|
|
|
|
noabort_decreasing
|
|
|
|
--------------------
|
|
|
|
|
|
|
|
(1 row)
|
|
|
|
|
|
|
|
FETCH NEXT FROM c;
|
|
|
|
noabort_decreasing
|
|
|
|
--------------------
|
|
|
|
|
|
|
|
(1 row)
|
|
|
|
|
|
|
|
FETCH NEXT FROM c;
|
|
|
|
noabort_decreasing
|
|
|
|
--------------------
|
|
|
|
(0 rows)
|
|
|
|
|
|
|
|
FETCH NEXT FROM c;
|
|
|
|
noabort_decreasing
|
|
|
|
--------------------
|
|
|
|
(0 rows)
|
|
|
|
|
|
|
|
FETCH BACKWARD FROM c;
|
|
|
|
noabort_decreasing
|
|
|
|
--------------------
|
|
|
|
|
|
|
|
(1 row)
|
|
|
|
|
|
|
|
FETCH NEXT FROM c;
|
|
|
|
noabort_decreasing
|
|
|
|
--------------------
|
|
|
|
(0 rows)
|
|
|
|
|
|
|
|
COMMIT;
|
|
|
|
-- disk based
|
|
|
|
BEGIN;
|
|
|
|
SET LOCAL enable_indexscan = false;
|
|
|
|
SET LOCAL work_mem = '100kB';
|
|
|
|
-- unfortunately can't show analyze output confirming sort method,
|
|
|
|
-- the memory used output wouldn't be stable
|
|
|
|
EXPLAIN (COSTS OFF) DECLARE c SCROLL CURSOR FOR SELECT noabort_decreasing FROM abbrev_abort_uuids ORDER BY noabort_decreasing;
|
|
|
|
QUERY PLAN
|
|
|
|
--------------------------------------
|
|
|
|
Sort
|
|
|
|
Sort Key: noabort_decreasing
|
|
|
|
-> Seq Scan on abbrev_abort_uuids
|
|
|
|
(3 rows)
|
|
|
|
|
|
|
|
DECLARE c SCROLL CURSOR FOR SELECT noabort_decreasing FROM abbrev_abort_uuids ORDER BY noabort_decreasing;
|
|
|
|
-- first and second
|
|
|
|
FETCH NEXT FROM c;
|
|
|
|
noabort_decreasing
|
|
|
|
--------------------------------------
|
|
|
|
00000000-0000-0000-0000-000000000000
|
|
|
|
(1 row)
|
|
|
|
|
|
|
|
FETCH NEXT FROM c;
|
|
|
|
noabort_decreasing
|
|
|
|
--------------------------------------
|
|
|
|
00000000-0000-0000-0000-000000000000
|
|
|
|
(1 row)
|
|
|
|
|
|
|
|
-- scroll beyond beginning
|
|
|
|
FETCH BACKWARD FROM c;
|
|
|
|
noabort_decreasing
|
|
|
|
--------------------------------------
|
|
|
|
00000000-0000-0000-0000-000000000000
|
|
|
|
(1 row)
|
|
|
|
|
|
|
|
FETCH BACKWARD FROM c;
|
|
|
|
noabort_decreasing
|
|
|
|
--------------------
|
|
|
|
(0 rows)
|
|
|
|
|
|
|
|
FETCH BACKWARD FROM c;
|
|
|
|
noabort_decreasing
|
|
|
|
--------------------
|
|
|
|
(0 rows)
|
|
|
|
|
|
|
|
FETCH BACKWARD FROM c;
|
|
|
|
noabort_decreasing
|
|
|
|
--------------------
|
|
|
|
(0 rows)
|
|
|
|
|
|
|
|
FETCH NEXT FROM c;
|
|
|
|
noabort_decreasing
|
|
|
|
--------------------------------------
|
|
|
|
00000000-0000-0000-0000-000000000000
|
|
|
|
(1 row)
|
|
|
|
|
2023-10-09 05:48:47 +02:00
|
|
|
-- scroll beyond end
|
2019-10-24 22:58:40 +02:00
|
|
|
FETCH LAST FROM c;
|
|
|
|
noabort_decreasing
|
|
|
|
--------------------
|
|
|
|
|
|
|
|
(1 row)
|
|
|
|
|
|
|
|
FETCH BACKWARD FROM c;
|
|
|
|
noabort_decreasing
|
|
|
|
--------------------
|
|
|
|
|
|
|
|
(1 row)
|
|
|
|
|
|
|
|
FETCH NEXT FROM c;
|
|
|
|
noabort_decreasing
|
|
|
|
--------------------
|
|
|
|
|
|
|
|
(1 row)
|
|
|
|
|
|
|
|
FETCH NEXT FROM c;
|
|
|
|
noabort_decreasing
|
|
|
|
--------------------
|
|
|
|
(0 rows)
|
|
|
|
|
|
|
|
FETCH NEXT FROM c;
|
|
|
|
noabort_decreasing
|
|
|
|
--------------------
|
|
|
|
(0 rows)
|
|
|
|
|
|
|
|
FETCH BACKWARD FROM c;
|
|
|
|
noabort_decreasing
|
|
|
|
--------------------
|
|
|
|
|
|
|
|
(1 row)
|
|
|
|
|
|
|
|
FETCH NEXT FROM c;
|
|
|
|
noabort_decreasing
|
|
|
|
--------------------
|
|
|
|
(0 rows)
|
|
|
|
|
|
|
|
COMMIT;
|
|
|
|
----
|
|
|
|
-- test tuplesort using both in-memory and disk sort
|
|
|
|
---
|
|
|
|
-- memory based
|
|
|
|
SELECT
|
|
|
|
-- fixed-width by-value datum
|
|
|
|
(array_agg(id ORDER BY id DESC NULLS FIRST))[0:5],
|
|
|
|
-- fixed-width by-ref datum
|
|
|
|
(array_agg(abort_increasing ORDER BY abort_increasing DESC NULLS LAST))[0:5],
|
|
|
|
-- variable-width datum
|
|
|
|
(array_agg(id::text ORDER BY id::text DESC NULLS LAST))[0:5],
|
|
|
|
-- fixed width by-value datum tuplesort
|
|
|
|
percentile_disc(0.99) WITHIN GROUP (ORDER BY id),
|
|
|
|
-- ensure state is shared
|
|
|
|
percentile_disc(0.01) WITHIN GROUP (ORDER BY id),
|
|
|
|
-- fixed width by-ref datum tuplesort
|
|
|
|
percentile_disc(0.8) WITHIN GROUP (ORDER BY abort_increasing),
|
|
|
|
-- variable width by-ref datum tuplesort
|
|
|
|
percentile_disc(0.2) WITHIN GROUP (ORDER BY id::text),
|
|
|
|
-- multi-column tuplesort
|
|
|
|
rank('00000000-0000-0000-0000-000000000000', '2', '2') WITHIN GROUP (ORDER BY noabort_increasing, id, id::text)
|
|
|
|
FROM (
|
|
|
|
SELECT * FROM abbrev_abort_uuids
|
|
|
|
UNION ALL
|
|
|
|
SELECT NULL, NULL, NULL, NULL, NULL) s;
|
|
|
|
array_agg | array_agg | array_agg | percentile_disc | percentile_disc | percentile_disc | percentile_disc | rank
|
|
|
|
--------------------------------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------------+-----------------+-----------------+--------------------------------------+-----------------+------
|
|
|
|
{NULL,20010,20009,20008,20007} | {00000000-0000-0000-0000-000000020000,00000000-0000-0000-0000-000000020000,00000000-0000-0000-0000-000000019999,00000000-0000-0000-0000-000000019998,00000000-0000-0000-0000-000000019997} | {9999,9998,9997,9996,9995} | 19810 | 200 | 00000000-0000-0000-0000-000000016003 | 136 | 2
|
|
|
|
(1 row)
|
|
|
|
|
|
|
|
-- disk based (see also above)
|
|
|
|
BEGIN;
|
|
|
|
SET LOCAL work_mem = '100kB';
|
|
|
|
SELECT
|
|
|
|
(array_agg(id ORDER BY id DESC NULLS FIRST))[0:5],
|
|
|
|
(array_agg(abort_increasing ORDER BY abort_increasing DESC NULLS LAST))[0:5],
|
|
|
|
(array_agg(id::text ORDER BY id::text DESC NULLS LAST))[0:5],
|
|
|
|
percentile_disc(0.99) WITHIN GROUP (ORDER BY id),
|
|
|
|
percentile_disc(0.01) WITHIN GROUP (ORDER BY id),
|
|
|
|
percentile_disc(0.8) WITHIN GROUP (ORDER BY abort_increasing),
|
|
|
|
percentile_disc(0.2) WITHIN GROUP (ORDER BY id::text),
|
|
|
|
rank('00000000-0000-0000-0000-000000000000', '2', '2') WITHIN GROUP (ORDER BY noabort_increasing, id, id::text)
|
|
|
|
FROM (
|
|
|
|
SELECT * FROM abbrev_abort_uuids
|
|
|
|
UNION ALL
|
|
|
|
SELECT NULL, NULL, NULL, NULL, NULL) s;
|
|
|
|
array_agg | array_agg | array_agg | percentile_disc | percentile_disc | percentile_disc | percentile_disc | rank
|
|
|
|
--------------------------------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------------+-----------------+-----------------+--------------------------------------+-----------------+------
|
|
|
|
{NULL,20010,20009,20008,20007} | {00000000-0000-0000-0000-000000020000,00000000-0000-0000-0000-000000020000,00000000-0000-0000-0000-000000019999,00000000-0000-0000-0000-000000019998,00000000-0000-0000-0000-000000019997} | {9999,9998,9997,9996,9995} | 19810 | 200 | 00000000-0000-0000-0000-000000016003 | 136 | 2
|
|
|
|
(1 row)
|
|
|
|
|
|
|
|
ROLLBACK;
|
|
|
|
----
|
|
|
|
-- test tuplesort mark/restore
|
|
|
|
---
|
2019-12-14 21:01:56 +01:00
|
|
|
CREATE TEMP TABLE test_mark_restore(col1 int, col2 int, col12 int);
|
2019-10-24 22:58:40 +02:00
|
|
|
-- need a few duplicates for mark/restore to matter
|
|
|
|
INSERT INTO test_mark_restore(col1, col2, col12)
|
|
|
|
SELECT a.i, b.i, a.i * b.i FROM generate_series(1, 500) a(i), generate_series(1, 5) b(i);
|
|
|
|
BEGIN;
|
|
|
|
SET LOCAL enable_nestloop = off;
|
|
|
|
SET LOCAL enable_hashjoin = off;
|
2019-11-14 01:36:31 +01:00
|
|
|
SET LOCAL enable_material = off;
|
2019-10-24 22:58:40 +02:00
|
|
|
-- set query into variable once, to avoid repetition of the fairly long query
|
|
|
|
SELECT $$
|
|
|
|
SELECT col12, count(distinct a.col1), count(distinct a.col2), count(distinct b.col1), count(distinct b.col2), count(*)
|
|
|
|
FROM test_mark_restore a
|
|
|
|
JOIN test_mark_restore b USING(col12)
|
|
|
|
GROUP BY 1
|
|
|
|
HAVING count(*) > 1
|
|
|
|
ORDER BY 2 DESC, 1 DESC, 3 DESC, 4 DESC, 5 DESC, 6 DESC
|
|
|
|
LIMIT 10
|
|
|
|
$$ AS qry \gset
|
|
|
|
-- test mark/restore with in-memory sorts
|
|
|
|
EXPLAIN (COSTS OFF) :qry;
|
|
|
|
QUERY PLAN
|
|
|
|
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------
|
|
|
|
Limit
|
|
|
|
-> Sort
|
|
|
|
Sort Key: (count(DISTINCT a.col1)) DESC, a.col12 DESC, (count(DISTINCT a.col2)) DESC, (count(DISTINCT b.col1)) DESC, (count(DISTINCT b.col2)) DESC, (count(*)) DESC
|
|
|
|
-> GroupAggregate
|
|
|
|
Group Key: a.col12
|
|
|
|
Filter: (count(*) > 1)
|
Improve performance of ORDER BY / DISTINCT aggregates
ORDER BY / DISTINCT aggreagtes have, since implemented in Postgres, been
executed by always performing a sort in nodeAgg.c to sort the tuples in
the current group into the correct order before calling the transition
function on the sorted tuples. This was not great as often there might be
an index that could have provided pre-sorted input and allowed the
transition functions to be called as the rows come in, rather than having
to store them in a tuplestore in order to sort them once all the tuples
for the group have arrived.
Here we change the planner so it requests a path with a sort order which
supports the most amount of ORDER BY / DISTINCT aggregate functions and
add new code to the executor to allow it to support the processing of
ORDER BY / DISTINCT aggregates where the tuples are already sorted in the
correct order.
Since there can be many ORDER BY / DISTINCT aggregates in any given query
level, it's very possible that we can't find an order that suits all of
these aggregates. The sort order that the planner chooses is simply the
one that suits the most aggregate functions. We take the most strictly
sorted variation of each order and see how many aggregate functions can
use that, then we try again with the order of the remaining aggregates to
see if another order would suit more aggregate functions. For example:
SELECT agg(a ORDER BY a),agg2(a ORDER BY a,b) ...
would request the sort order to be {a, b} because {a} is a subset of the
sort order of {a,b}, but;
SELECT agg(a ORDER BY a),agg2(a ORDER BY c) ...
would just pick a plan ordered by {a} (we give precedence to aggregates
which are earlier in the targetlist).
SELECT agg(a ORDER BY a),agg2(a ORDER BY b),agg3(a ORDER BY b) ...
would choose to order by {b} since two aggregates suit that vs just one
that requires input ordered by {a}.
Author: David Rowley
Reviewed-by: Ronan Dunklau, James Coleman, Ranier Vilela, Richard Guo, Tom Lane
Discussion: https://postgr.es/m/CAApHDvpHzfo92%3DR4W0%2BxVua3BUYCKMckWAmo-2t_KiXN-wYH%3Dw%40mail.gmail.com
2022-08-02 13:11:45 +02:00
|
|
|
-> Incremental Sort
|
|
|
|
Sort Key: a.col12 DESC, a.col1
|
|
|
|
Presorted Key: a.col12
|
|
|
|
-> Merge Join
|
|
|
|
Merge Cond: (a.col12 = b.col12)
|
|
|
|
-> Sort
|
|
|
|
Sort Key: a.col12 DESC
|
|
|
|
-> Seq Scan on test_mark_restore a
|
|
|
|
-> Sort
|
|
|
|
Sort Key: b.col12 DESC
|
|
|
|
-> Seq Scan on test_mark_restore b
|
|
|
|
(17 rows)
|
2019-10-24 22:58:40 +02:00
|
|
|
|
|
|
|
:qry;
|
|
|
|
col12 | count | count | count | count | count
|
|
|
|
-------+-------+-------+-------+-------+-------
|
|
|
|
480 | 5 | 5 | 5 | 5 | 25
|
|
|
|
420 | 5 | 5 | 5 | 5 | 25
|
|
|
|
360 | 5 | 5 | 5 | 5 | 25
|
|
|
|
300 | 5 | 5 | 5 | 5 | 25
|
|
|
|
240 | 5 | 5 | 5 | 5 | 25
|
|
|
|
180 | 5 | 5 | 5 | 5 | 25
|
|
|
|
120 | 5 | 5 | 5 | 5 | 25
|
|
|
|
60 | 5 | 5 | 5 | 5 | 25
|
|
|
|
960 | 4 | 4 | 4 | 4 | 16
|
|
|
|
900 | 4 | 4 | 4 | 4 | 16
|
|
|
|
(10 rows)
|
|
|
|
|
|
|
|
-- test mark/restore with on-disk sorts
|
|
|
|
SET LOCAL work_mem = '100kB';
|
|
|
|
EXPLAIN (COSTS OFF) :qry;
|
|
|
|
QUERY PLAN
|
|
|
|
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------
|
|
|
|
Limit
|
|
|
|
-> Sort
|
|
|
|
Sort Key: (count(DISTINCT a.col1)) DESC, a.col12 DESC, (count(DISTINCT a.col2)) DESC, (count(DISTINCT b.col1)) DESC, (count(DISTINCT b.col2)) DESC, (count(*)) DESC
|
|
|
|
-> GroupAggregate
|
|
|
|
Group Key: a.col12
|
|
|
|
Filter: (count(*) > 1)
|
Improve performance of ORDER BY / DISTINCT aggregates
ORDER BY / DISTINCT aggreagtes have, since implemented in Postgres, been
executed by always performing a sort in nodeAgg.c to sort the tuples in
the current group into the correct order before calling the transition
function on the sorted tuples. This was not great as often there might be
an index that could have provided pre-sorted input and allowed the
transition functions to be called as the rows come in, rather than having
to store them in a tuplestore in order to sort them once all the tuples
for the group have arrived.
Here we change the planner so it requests a path with a sort order which
supports the most amount of ORDER BY / DISTINCT aggregate functions and
add new code to the executor to allow it to support the processing of
ORDER BY / DISTINCT aggregates where the tuples are already sorted in the
correct order.
Since there can be many ORDER BY / DISTINCT aggregates in any given query
level, it's very possible that we can't find an order that suits all of
these aggregates. The sort order that the planner chooses is simply the
one that suits the most aggregate functions. We take the most strictly
sorted variation of each order and see how many aggregate functions can
use that, then we try again with the order of the remaining aggregates to
see if another order would suit more aggregate functions. For example:
SELECT agg(a ORDER BY a),agg2(a ORDER BY a,b) ...
would request the sort order to be {a, b} because {a} is a subset of the
sort order of {a,b}, but;
SELECT agg(a ORDER BY a),agg2(a ORDER BY c) ...
would just pick a plan ordered by {a} (we give precedence to aggregates
which are earlier in the targetlist).
SELECT agg(a ORDER BY a),agg2(a ORDER BY b),agg3(a ORDER BY b) ...
would choose to order by {b} since two aggregates suit that vs just one
that requires input ordered by {a}.
Author: David Rowley
Reviewed-by: Ronan Dunklau, James Coleman, Ranier Vilela, Richard Guo, Tom Lane
Discussion: https://postgr.es/m/CAApHDvpHzfo92%3DR4W0%2BxVua3BUYCKMckWAmo-2t_KiXN-wYH%3Dw%40mail.gmail.com
2022-08-02 13:11:45 +02:00
|
|
|
-> Incremental Sort
|
|
|
|
Sort Key: a.col12 DESC, a.col1
|
|
|
|
Presorted Key: a.col12
|
|
|
|
-> Merge Join
|
|
|
|
Merge Cond: (a.col12 = b.col12)
|
|
|
|
-> Sort
|
|
|
|
Sort Key: a.col12 DESC
|
|
|
|
-> Seq Scan on test_mark_restore a
|
|
|
|
-> Sort
|
|
|
|
Sort Key: b.col12 DESC
|
|
|
|
-> Seq Scan on test_mark_restore b
|
|
|
|
(17 rows)
|
2019-10-24 22:58:40 +02:00
|
|
|
|
|
|
|
:qry;
|
|
|
|
col12 | count | count | count | count | count
|
|
|
|
-------+-------+-------+-------+-------+-------
|
|
|
|
480 | 5 | 5 | 5 | 5 | 25
|
|
|
|
420 | 5 | 5 | 5 | 5 | 25
|
|
|
|
360 | 5 | 5 | 5 | 5 | 25
|
|
|
|
300 | 5 | 5 | 5 | 5 | 25
|
|
|
|
240 | 5 | 5 | 5 | 5 | 25
|
|
|
|
180 | 5 | 5 | 5 | 5 | 25
|
|
|
|
120 | 5 | 5 | 5 | 5 | 25
|
|
|
|
60 | 5 | 5 | 5 | 5 | 25
|
|
|
|
960 | 4 | 4 | 4 | 4 | 16
|
|
|
|
900 | 4 | 4 | 4 | 4 | 16
|
|
|
|
(10 rows)
|
|
|
|
|
|
|
|
COMMIT;
|