ืืขืช ืืขืช, ืืชืขืืจืจืช ืืืฉืืื ืฉื ืืืคืืฉ ื ืชืื ืื ืงืฉืืจืื ืืืืฆืขืืช ืงืืืฆืช ืืคืชืืืช. ืขื ืฉื ืงืื ืืช ืืืกืคืจ ืืืืื ืื ืืจืฉ ืฉื ืจืฉืืืืช.
ืืืืืื ืืื "ืืืืื ืืืืืชืืื" ืืื ืืืฆืื 20 ืืืขืืืช ืืขืชืืงืืช ืืืืชืจ, ืืจืฉืืื ืืจืฉืืืช ืืขืืืืื (ืืืืืื, ืืชืื ืืืืื ืืืช). ืขืืืจ "ืืืืืช ืืืืื ืื" ืฉืื ืื ืฉื ื ืืืื ืขื ืกืืืืืื ืงืฆืจืื ืฉื ืชืืืื ืขืืืื, ื ืืฉื ืืืื ื ืืจืฉ ืืขืชืื ืงืจืืืืช ืืืื.
ืืืืืจ ืื ื ืืื ืืืฉืื ื-PostgreSQL ืฉื โโืคืชืจืื "ื ืืืื" ืืืขืื ืืื, ืืืืืจืืชื "ืืื" ืืืืจืื ืืืื "ืืืืื" ื-SQL ืขื ืชื ืื ืืฆืืื ืืื ืชืื ืื ืฉื ืืฆืื, ืฉืืืื ืืืืืช ืฉืืืืฉื ืื ืืคืืชืื ืืืื ืืื ืืฉืืืืฉ ืืืงืจืื ืืืืื ืืืจืื.
ืืื ื ืืงื ืืขืจื ื ืชืื ื ืืืืงื
CREATE INDEX ON task(owner_id, task_date, id);
-- ะฐ ััะฐััะน - ัะดะฐะปะธะผ
DROP INDEX task_owner_id_task_date_idx;
ืืื ืฉื ืฉืืข, ืื ืืชืื
ืจืืฉืืช, ืืืื ื ืฉืจืื ืืช ืืืจืกื ืืคืฉืืื ืืืืชืจ ืฉื ืืืงืฉื, ืชืื ืืขืืจืช ืชืขืืืืช ืืืืืช ืฉื ืืืืฆืขืื
SELECT
*
FROM
task
WHERE
owner_id = ANY('{1,2,4,8,16,32,64,128,256,512}'::integer[])
ORDER BY
task_date, id
LIMIT 20;
ืงืฆืช ืขืฆืื - ืืืื ื ืจืง 20 ืชืงืืืืื, ืืื ืืื ืืงืก ืกืจืืงื ืืืืืจื ืื ื 960 ืฉืืจืืช, ืฉืื ืื ืืื ืฆืจืื ืืืืื... ืืืื ื ื ืกื ืืงืจืื ืคืืืช.
unnest + ARRAY
ืืฉืืงืื ืืจืืฉืื ืฉืืขืืืจ ืื ื ืืื ืื ื ืฆืืจื ืจืง 20 ืืืืื ืื ืจืฉืืืืช, ืืื ืคืฉืื ืืงืจืื ืื ืืืชืจ ื-20 ืืืืื ืื ืืืืชื ืกืืจ ืขืืืจ ืื ืืื ืึทืคึฐืชึตืึท. ืืึนื, ืืื ืืงืก ืืชืืื (owner_id, task_date, id) ืืฉ ืื ื.
ืืืื ื ืฉืชืืฉ ืืืืชื ืื ืื ืื ืืืืืืฅ ื"ืืชืคืฉืืืช ืืขืืืืืช" ืจืฉืืืช ืืืื ืืื ืืืจืืืช, ืืื ื ARRAY()
:
WITH T AS (
SELECT
unnest(ARRAY(
SELECT
t
FROM
task t
WHERE
owner_id = unnest
ORDER BY
task_date, id
LIMIT 20 -- ะพะณัะฐะฝะธัะธะฒะฐะตะผ ััั...
)) r
FROM
unnest('{1,2,4,8,16,32,64,128,256,512}'::integer[])
)
SELECT
(r).*
FROM
T
ORDER BY
(r).task_date, (r).id
LIMIT 20; -- ... ะธ ััั - ัะพะถะต
ืื, ืืจืื ืืืชืจ ืืื ืืืจ! ืืืืจ ืืืชืจ ื-40% ืืคื 4.5 ืคืืืช ื ืชืื ืื ืืืืชื ืืืื ืืงืจืื ืืืชื.
ืืชืืืฉืืช ืฉื ืจืฉืืืืช ืืืื ืืืืฆืขืืช CTEืืจืฉื ืื ืืืคื ืืช ืืช ืชืฉืืืช ืืืื ืืขืืืื ืืืช ืืืงืจืื ืืกืืืืื ื ืืกืืื ืืขืืื ืืื ืขื ืืฉืืืช ืฉื ืจืฉืืื ืืืืจ ืืืคืืฉ ืืืจืื ืืฉืืืืชืช ืืฉื ื, ืืืื "ืืขืืืฃ" ืืืชื ื-CTE, ืืืื ืืืืืื ื "ืืืืคืื" ืืช InitPlan ืคืจืืคืืจืฆืืื ืื ืืืกืคืจ ืฉื ืืืชื ืฉืืืช:
SELECT
((
SELECT
t
FROM
task t
WHERE
owner_id = 1
ORDER BY
task_date, id
LIMIT 1
).*);
Result (cost=4.77..4.78 rows=1 width=16) (actual time=0.063..0.063 rows=1 loops=1)
Buffers: shared hit=16
InitPlan 1 (returns $0)
-> Limit (cost=0.42..1.19 rows=1 width=48) (actual time=0.031..0.032 rows=1 loops=1)
Buffers: shared hit=4
-> Index Scan using task_owner_id_task_date_id_idx on task t (cost=0.42..387.57 rows=500 width=48) (actual time=0.030..0.030 rows=1 loops=1)
Index Cond: (owner_id = 1)
Buffers: shared hit=4
InitPlan 2 (returns $1)
-> Limit (cost=0.42..1.19 rows=1 width=48) (actual time=0.008..0.009 rows=1 loops=1)
Buffers: shared hit=4
-> Index Scan using task_owner_id_task_date_id_idx on task t_1 (cost=0.42..387.57 rows=500 width=48) (actual time=0.008..0.008 rows=1 loops=1)
Index Cond: (owner_id = 1)
Buffers: shared hit=4
InitPlan 3 (returns $2)
-> Limit (cost=0.42..1.19 rows=1 width=48) (actual time=0.008..0.008 rows=1 loops=1)
Buffers: shared hit=4
-> Index Scan using task_owner_id_task_date_id_idx on task t_2 (cost=0.42..387.57 rows=500 width=48) (actual time=0.008..0.008 rows=1 loops=1)
Index Cond: (owner_id = 1)
Buffers: shared hit=4"
InitPlan 4 (returns $3)
-> Limit (cost=0.42..1.19 rows=1 width=48) (actual time=0.009..0.009 rows=1 loops=1)
Buffers: shared hit=4
-> Index Scan using task_owner_id_task_date_id_idx on task t_3 (cost=0.42..387.57 rows=500 width=48) (actual time=0.009..0.009 rows=1 loops=1)
Index Cond: (owner_id = 1)
Buffers: shared hit=4
ืืืชื ืจืฉืืื "ื ืืืงื" 4 ืคืขืืื... ืขื PostgreSQL 11, ืืชื ืืืืช ืื ืืชืจืืฉืช ืืืืคื ืงืืืข, ืืืคืชืจืื ืืื "ืืขืืืฃ" ืืืชื ื-CTE, ืฉืืื ืืืื ืืืืื ืืืืคืืืืืืจ ืืืจืกืืืช ืืื.
ืืฆืืจ ืจืงืืจืกืืื
ืืืจืกื ืืงืืืืช, ืืกื ืืื ืงืจืื ื 200 ืฉืืจืืช ืืืขื ื-20 ืื ืืจืฉืื. ืื 960, ืืื ืืคืืื ืคืืืช - ืืื ืื ืืคืฉืจื?
ืืืื ื ื ืกื ืืืฉืชืืฉ ืืืืข ืฉืื ืื ื ืฆืจืืืื ืกื"ื ืจืฉืืืืช. ืืืืืจ, ื ืืืืจ ืขื ืงืจืืืช ื ืชืื ืื ืจืง ืขื ืฉื ืืืข ืืืืืช ืฉืื ื ืฆืจืืืื.
ืฉืื 1: ืจืฉืืืช ืืชืืืืช
ืืจืืจ, ืจืฉืืืช ื"ืืืจื" ืฉืื ื ืฉื 20 ืจืฉืืืืช ืฆืจืืื ืืืชืืื ืืจืฉืืืืช ื"ืจืืฉืื ืืช" ืขืืืจ ืืื ืืืคืชืืืช ื-owner_id ืฉืื ื. ืืื, ืจืืฉืืช ื ืืฆื ืืืื "ืจืืฉืื ืืืื" ืขืืืจ ืื ืืื ืืืืคืชืืืช ืืืืืกืืฃ ืืืชื ืืจืฉืืื, ืืืืื ืืืชื ืืคื ืืกืืจ ืฉืื ืื ื ืจืืฆืื - (ืชืืจืื_ืืฉืืื, ืืืื).
ืฉืื 2: ืืฆื ืืช ืืขืจืืื "ืืืืื".
ืขืืฉืื ืื ื ืืงื ืืช ืืขืจื ืืจืืฉืื ืืืจืฉืืื ืฉืื ื ืื ืชืืื "ืฆืขื" ืืืื ืืืืจื ืืืื ืืงืก ืฉืืืจื ืขื ืืคืชื owner_id, ืื ืื ืืจืฉืืืืช ืฉื ืืฆืื ืื ืืืืืง ืืืืืช ืืืืืจื ืฉืืชืงืืื. ืืืืื, ืจืง ืขื ืฉื ืืฆื ืืช ืืคืชื ืืชืืช ืขืจื ืฉื ื ืืจืฉืืื.
ืื ืืชืืจืจ ืฉ"ืืฆืื ื" ืืช ืืฉืื ืืฉื ื, ืื ืืฉ ืืืืกืืฃ ืืช ืืขืจื ืืืืจืื ืฉื ืงืจื ืืจืฉืืื ืืืงืื ืืจืืฉืื (ืขื ืืืชื owner_id), ืฉืืืืจืื ืื ื ืืืืื ืื ืืืืฉ ืืช ืืจืฉืืื ืฉืื.
ืืืืืจ, ืชืืื ื ืงืื ืฉืืจืฉืืื ืืื ืืืชืจ ืืื ืืกื ืืืช ืืื ืืื ืืืืคืชืืืช (ืื ื ืืืจื ืืขืจืืื ืืื "ื ืืฆื", ืืจื ืฉืืขืจื ืืจืืฉืื ืืืจืฉืืื ืคืฉืื ืืืขืื ืืื ืืชืืืกืฃ ืืืื ), ืืื ืชืืื ืืกืืืจ ืืกืืจ ืขืืื ืฉื ืืคืชื ืืืคืืืงืฆืื (ืชืืจืื_ืืฉืืื, ืืืื).
ืฉืื 3: ืกืื ืื ื"ืืจืื" ืจืฉืืืืช
ืืืืง ืืืฉืืจืืช ืฉื ืืืืืจื ืืจืงืืจืกืืืืช ืฉืื ื, ืืื ืจืฉืืืืช rv
ืืฉืืืคืืื - ืชืืืื ืื ื ืืืฆืืื ืืืื "ืืฆืืืช ืืืืื ืฉื ืืขืจื ืืฉื ื ืืจืฉืืื", ืืืืืจ ืืื ืืืืืคืื ืืืชื ืืชืืจ ืืจืืฉืื ืืืจืฉืืื. ืื ืฆืจืื ืืกื ื ืืช ืืืชืจืืฉืืช ืืจืืฉืื ื.
ืืฉืืืืชื ืืกืืคืืช ืืืคืืืื
WITH RECURSIVE T AS (
-- #1 : ะทะฐะฝะพัะธะผ ะฒ ัะฟะธัะพะบ "ะฟะตัะฒัะต" ะทะฐะฟะธัะธ ะฟะพ ะบะฐะถะดะพะผั ะธะท ะบะปััะตะน ะฝะฐะฑะพัะฐ
WITH wrap AS ( -- "ะผะฐัะตัะธะฐะปะธะทัะตะผ" record'ั, ััะพะฑั ะพะฑัะฐัะตะฝะธะต ะบ ะฟะพะปัะผ ะฝะต ะฒัะทัะฒะฐะปะพ ัะผะฝะพะถะตะฝะธั InitPlan/SubPlan
WITH T AS (
SELECT
(
SELECT
r
FROM
task r
WHERE
owner_id = unnest
ORDER BY
task_date, id
LIMIT 1
) r
FROM
unnest('{1,2,4,8,16,32,64,128,256,512}'::integer[])
)
SELECT
array_agg(r ORDER BY (r).task_date, (r).id) list -- ัะพััะธััะตะผ ัะฟะธัะพะบ ะฒ ะฝัะถะฝะพะผ ะฟะพััะดะบะต
FROM
T
)
SELECT
list
, list[1] rv
, FALSE not_cross
, 0 size
FROM
wrap
UNION ALL
-- #2 : ะฒััะธััะฒะฐะตะผ ะทะฐะฟะธัะธ 1-ะณะพ ะฟะพ ะฟะพััะดะบั ะบะปััะฐ, ะฟะพะบะฐ ะฝะต ะฟะตัะตัะฐะณะฝะตะผ ัะตัะตะท ะทะฐะฟะธัั 2-ะณะพ
SELECT
CASE
-- ะตัะปะธ ะฝะธัะตะณะพ ะฝะต ะฝะฐะนะดะตะฝะพ ะดะปั ะบะปััะฐ 1-ะน ะทะฐะฟะธัะธ
WHEN X._r IS NOT DISTINCT FROM NULL THEN
T.list[2:] -- ัะฑะธัะฐะตะผ ะตะต ะธะท ัะฟะธัะบะฐ
-- ะตัะปะธ ะผั ะะ ะฟะตัะตัะตะบะปะธ ะฟัะธะบะปะฐะดะฝะพะน ะบะปัั 2-ะน ะทะฐะฟะธัะธ
WHEN X.not_cross THEN
T.list -- ะฟัะพััะพ ะฟัะพััะณะธะฒะฐะตะผ ัะพั ะถะต ัะฟะธัะพะบ ะฑะตะท ะผะพะดะธัะธะบะฐัะธะน
-- ะตัะปะธ ะฒ ัะฟะธัะบะต ัะถะต ะฝะตั 2-ะน ะทะฐะฟะธัะธ
WHEN T.list[2] IS NULL THEN
-- ะฟัะพััะพ ะฒะพะทะฒัะฐัะฐะตะผ ะฟัััะพะน ัะฟะธัะพะบ
'{}'
-- ะฟะตัะตัะพััะธัะพะฒัะฒะฐะตะผ ัะปะพะฒะฐัั, ัะฑะธัะฐั 1-ั ะทะฐะฟะธัั ะธ ะดะพะฑะฐะฒะปัั ะฟะพัะปะตะดะฝัั ะธะท ะฝะฐะนะดะตะฝะฝัั
ELSE (
SELECT
coalesce(T.list[2] || array_agg(r ORDER BY (r).task_date, (r).id), '{}')
FROM
unnest(T.list[3:] || X._r) r
)
END
, X._r
, X.not_cross
, T.size + X.not_cross::integer
FROM
T
, LATERAL(
WITH wrap AS ( -- "ะผะฐัะตัะธะฐะปะธะทัะตะผ" record
SELECT
CASE
-- ะตัะปะธ ะฒัะต-ัะฐะบะธ "ะฟะตัะตัะฐะณะฝัะปะธ" ัะตัะตะท 2-ั ะทะฐะฟะธัั
WHEN NOT T.not_cross
-- ัะพ ะฝัะถะฝะฐั ะทะฐะฟะธัั - ะฟะตัะฒะฐั ะธะท ัะฟะฟะธัะบะฐ
THEN T.list[1]
ELSE ( -- ะตัะปะธ ะฝะต ะฟะตัะตัะตะบะปะธ, ัะพ ะบะปัั ะพััะฐะปัั ะบะฐะบ ะฒ ะฟัะตะดัะดััะตะน ะทะฐะฟะธัะธ - ะพััะฐะปะบะธะฒะฐะตะผัั ะพั ะฝะตะต
SELECT
_r
FROM
task _r
WHERE
owner_id = (rv).owner_id AND
(task_date, id) > ((rv).task_date, (rv).id)
ORDER BY
task_date, id
LIMIT 1
)
END _r
)
SELECT
_r
, CASE
-- ะตัะปะธ 2-ะน ะทะฐะฟะธัะธ ัะถะต ะฝะตั ะฒ ัะฟะธัะบะต, ะฝะพ ะผั ั
ะพัั ััะพ-ัะพ ะฝะฐัะปะธ
WHEN list[2] IS NULL AND _r IS DISTINCT FROM NULL THEN
TRUE
ELSE -- ะฝะธัะตะณะพ ะฝะต ะฝะฐัะปะธ ะธะปะธ "ะฟะตัะตัะฐะณะฝัะปะธ"
coalesce(((_r).task_date, (_r).id) < ((list[2]).task_date, (list[2]).id), FALSE)
END not_cross
FROM
wrap
) X
WHERE
T.size < 20 AND -- ะพะณัะฐะฝะธัะธะฒะฐะตะผ ััั ะบะพะปะธัะตััะฒะพ
T.list IS DISTINCT FROM '{}' -- ะธะปะธ ะฟะพะบะฐ ัะฟะธัะพะบ ะฝะต ะบะพะฝัะธะปัั
)
-- #3 : "ัะฐะทะฒะพัะฐัะธะฒะฐะตะผ" ะทะฐะฟะธัะธ - ะฟะพััะดะพะบ ะณะฐัะฐะฝัะธัะพะฒะฐะฝ ะฟะพ ะฟะพัััะพะตะฝะธั
SELECT
(rv).*
FROM
T
WHERE
not_cross; -- ะฑะตัะตะผ ัะพะปัะบะพ "ะฝะตะฟะตัะตัะตะบะฐััะธะต" ะทะฐะฟะธัะธ
ืืคืืื, ืื ืื ื ื ืกืืจ ื-50% ืืงืจืืืืช ืื ืชืื ืื ืืืฉื 20% ืืืื ืืืืฆืืข. ืืืืืจ, ืื ืืฉ ืื ืกืืืืช ืืืืืื ืฉืืงืจืืื ืขืฉืืื ืืืืืฉื ืืื ืจื (ืืืืืื, ืื ืชืื ืื ืืจืื ืืื ื ืืงืืืฅ ื-Cache, ืืืชื ืฆืจืื ืืืืช ืืืืกืง ืืฉืืื ืื), ืื ืืืจื ืื ืืชื ืืืื ืืืืืช ืคืืืช ืชืืื ืืงืจืืื .
ืืื ืืงืจื, ืืื ืืืืฆืืข ืืชืืจืจ ืืืื ืืืชืจ ืืืฉืจ ืืืืคืฆืื ืืจืืฉืื ื ื"ื ืืืืืช". ืืื ืืืืื ืืฉืืืฉ ืืืคืฉืจืืืืช ืืืื ืืืฉืชืืฉ ืชืืื ืื.
ืืงืืจ: www.habr.com