Использую СУБД PGSQL.
Есть таблица Documents в ней поле Account - целое, User - массив строк.
Происходит удаление пользователя, нужно этого пользователя удалить из User,
если после удаления массив пустой, то нужно удалить запись.
Написал такой запрос, но он стал жутко тормозить.
| Код |
WITH user AS (
SELECT DISTINCT UNNEST(ARRAY['27672','6145']) AS "Id"
),
ar AS(
SELECT
"@Id" AS "Id",
array_remove("User", user."Id") AS "NewUser",
CASE
WHEN array_length(array_remove("User", user."Id"), 1) > 0 THEN FALSE
ELSE TRUE
END AS "NeedDelete"
FROM "Documents" ar, user
WHERE
"Account" = 4777912 AND
array_position(ar."User", user."Id") IS NOT NULL
),
delete_ar AS(
DELETE FROM "Documents"
USING ar
WHERE "@Id" = ar."Id" AND
ar."NeedDelete" IS TRUE
)
UPDATE "Documents"
SET "User" = ar."NewUser"
FROM ar
WHERE ar."Id" = "@Id" AND
ar."NeedDelete" IS FALSE
|
| Код |
Update on "Documents" (cost=19771027.17..22312135.48 rows=2074177 width=134) (actual time=188992.755..188992.755 rows=0 loops=1)
Buffers: shared hit=22742 read=2790563 dirtied=121272 written=56091, temp read=8246 written=1402207
CTE user
-> HashAggregate (cost=0.02..0.52 rows=100 width=32) (actual time=0.007..0.010 rows=2 loops=1)
Group Key: unnest('{27672,6145}'::text[])
-> Result (cost=0.00..0.01 rows=1 width=32) (actual time=0.003..0.004 rows=2 loops=1)
CTE ar
-> Nested Loop (cost=0.57..237640.03 rows=4148354 width=37) (actual time=59.829..484.828 rows=44 loops=1)
Join Filter: (array_position(ar_1."User", user."Id") IS NOT NULL)
Rows Removed by Join Filter: 24234
Buffers: shared hit=7660 read=1433 dirtied=13
-> CTE Scan on user (cost=0.00..2.00 rows=100 width=32) (actual time=0.008..0.015 rows=2 loops=1)
-> Materialize (cost=0.57..133720.72 rows=41692 width=35) (actual time=0.649..236.659 rows=12139 loops=2)
Buffers: shared hit=7660 read=1433 dirtied=13
-> Index Scan using "iDocuments-AccountDocument" on "Documents" ar_1 (cost=0.57..133512.26 rows=41692 width=35) (actual time=1.296..466.032 rows=12139 loops=1)
Index Cond: ("Account" = '4777912'::bigint)
Buffers: shared hit=7660 read=1433 dirtied=13
CTE delete_ar
-> Delete on "Documents" "Documents_1" (cost=8512344.15..10206749.46 rows=2074177 width=34) (actual time=148112.808..148112.808 rows=0 loops=1)
Buffers: shared hit=3422 read=2800776 dirtied=29, temp read=59703 written=801388
-> Hash Join (cost=8512344.15..10206749.46 rows=2074177 width=34) (actual time=143942.901..148111.006 rows=38 loops=1)
Hash Cond: (ar_2."Id" = "Documents_1"."@Id")
Buffers: shared hit=3388 read=2800772 dirtied=3, temp read=59703 written=801388
-> CTE Scan on ar ar_2 (cost=0.00..82967.08 rows=2074177 width=32) (actual time=0.030..0.104 rows=38 loops=1)
Filter: ("NeedDelete" IS TRUE)
Rows Removed by Filter: 6
-> Hash (cost=4888739.29..4888739.29 rows=208459029 width=10) (actual time=143820.738..143820.738 rows=205483044 loops=1)
Buckets: 1048576 Batches: 512 Memory Usage: 25459kB
Buffers: shared hit=3388 read=2800772 dirtied=3, temp written=800839
-> Seq Scan on "Documents" "Documents_1" (cost=0.00..4888739.29 rows=208459029 width=10) (actual time=0.040..85509.087 rows=205483044 loops=1)
Buffers: shared hit=3388 read=2800772 dirtied=3
-> Hash Join (cost=9326637.15..11867745.46 rows=2074177 width=134) (actual time=187388.784..188988.878 rows=6 loops=1)
Hash Cond: (ar."Id" = "Documents"."@Id")
Buffers: shared hit=22689 read=2790553 dirtied=121259 written=56091, temp read=8246 written=1402207
-> CTE Scan on ar (cost=0.00..82967.08 rows=2074177 width=96) (actual time=297.173..484.991 rows=6 loops=1)
Filter: ("NeedDelete" IS FALSE)
Rows Removed by Filter: 38
Buffers: shared hit=7660 read=1433 dirtied=13
-> Hash (cost=4888739.29..4888739.29 rows=208459029 width=42) (actual time=186809.680..186809.680 rows=205483044 loops=1)
Buckets: 524288 Batches: 1024 Memory Usage: 17420kB
Buffers: shared hit=15029 read=2789120 dirtied=121246 written=56091, temp written=1401178
-> Seq Scan on "Documents" (cost=0.00..4888739.29 rows=208459029 width=42) (actual time=0.712..100785.196 rows=205483044 loops=1)
Buffers: shared hit=15029 read=2789120 dirtied=121246 written=56091
|
Хочется переписать запрос, чтобы не было seq scan,
а использовался индекс @Id из Documents при удалении и обновлении записей
|