我有一个SQL视图（CREATE OR REPLACE VIEW table_view AS ...），该视图有20列，包含文本，整数，布尔值和整数数组字段。总共有九列是整数数组。
在绝大多数情况下，这种观点都非常有效。但是，当一行显示的整数数组中共有约50个值时，查询速度将减慢。这些列不会被查询，它们只是结果集的一部分，但是如果返回的行包含大量整数数组值，则查询的大小从〜250ms变为〜7s。
这是一个示例查询：
SELECT
"table_view"."id", -- integer
"table_view"."start", -- date with tz
"table_view"."end", -- date with tz
"table_view"."a_id", -- integer
"table_view"."c_id", -- integer
"table_view"."generator_id", -- integer
"table_view"."ci_id", -- integer
"table_view"."kind", -- integer
"table_view"."hidden", -- boolean
"table_view"."is_done", -- integer
"table_view"."title", -- text
"table_view"."c_type", -- integer
"table_view"."ci_title", -- integer
"table_view"."status", -- text
"table_view"."cs", -- integer array
"table_view"."cts", -- integer array
"table_view"."ts", -- integer array
"table_view"."tas", -- integer array
"table_view"."bs", -- integer array
"table_view"."ms", -- integer array
"table_view"."pcs", -- integer array
"table_view"."pts", -- integer array
"table_view"."ks" -- integer array
FROM
"table_view"
WHERE (
"table_view"."a_id" = 3289
AND (
"table_view"."cs" && ARRAY[28890, 21166, 28891, 29581, 29583, 22378, 22380, 22733, 28924, 28925, 28926, 28927, 28478, 41014]::integer[]
OR "table_view"."ms" && ARRAY[11125]::integer[]
) AND NOT (
"table_view"."hidden" = true
AND NOT (
"table_view"."ms" && ARRAY[11125]::integer[]
)
) AND "table_view"."end" >= '2019-02-03T00:00:00+00:00'::timestamptz
AND "table_view"."start" < '2019-04-15T00:00:00+00:00'::timestamptz
);
如果所有行的整数数组值之和都不大于50，则查询时间为50ms至250ms。
Time: 50.417 ms
但是，如果一个或多个行的整数数组值之和<〜50，则查询时间为〜6.5s至7s。
Time: 6737.154 ms
我已经使该查询中的某些列名称变得晦涩难懂，但这不会影响此问题的调试。我为此感到不安。我在网上进行的研究都没有提到列长是结果查询中的问题。
这是EXPLAIN ANALYZE的“错误”查询的输出：
Subquery Scan on table_view (cost=173.16..173.29 rows=1 width=436) (actual time=648.470..800.577 rows=60 loops=1)
-> GroupAggregate (cost=173.16..173.28 rows=1 width=103) (actual time=648.468..800.552 rows=60 loops=1)
Group Key: dhci.id, wfciwf.id, dutm.account_id
Filter: (((array_append('{}'::integer[], dhci.cid) && '{28890,21166,28891,29581,29583,22378,22380,22733,28924,28925,28926,28927,28478,41014}'::integer[]) OR (array_agg(DISTIN
CT dhamti.member_id) && '{11125}'::integer[])) AND ((NOT dhci.hidden) OR (array_agg(DISTINCT dhamti.member_id) && '{11125}'::integer[])))
-> Sort (cost=173.16..173.17 rows=1 width=103) (actual time=647.727..685.155 rows=172000 loops=1)
Sort Key: dhci.id, wfciwf.id, dutm.account_id
Sort Method: external merge Disk: 16392kB
-> Nested Loop Left Join (cost=68.45..173.15 rows=1 width=103) (actual time=1.033..478.844 rows=172000 loops=1)
-> Nested Loop Left Join (cost=68.16..171.71 rows=1 width=99) (actual time=1.017..308.168 rows=172000 loops=1)
-> Nested Loop Left Join (cost=67.87..170.20 rows=1 width=95) (actual time=0.997..126.331 rows=172000 loops=1)
-> Nested Loop Left Join (cost=67.58..168.77 rows=1 width=91) (actual time=0.978..26.478 rows=33400 loops=1)
-> Nested Loop Left Join (cost=67.16..165.68 rows=1 width=87) (actual time=0.960..4.997 rows=3700 loops=1)
-> Nested Loop Left Join (cost=66.73..162.71 rows=1 width=83) (actual time=0.949..2.572 rows=410 loops=1)
-> Nested Loop Left Join (cost=66.44..161.59 rows=1 width=79) (actual time=0.939..2.121 rows=60 loops=1)
-> Nested Loop (cost=66.02..154.64 rows=1 width=75) (actual time=0.926..1.818 rows=60 loops=1)
-> Nested Loop (cost=65.59..148.07 rows=1 width=66) (actual time=0.902..1.446 rows=60 loops=1)
-> Index Scan using dutm_8a089c2a on dutm (cost=0.29..9.40 rows=2 width=8) (actual time=0.017..0.028 rows=9 loops=1)
Index Cond: (account_id = 3289)
-> Bitmap Heap Scan on dhci (cost=65.31..69.33 rows=1 width=66) (actual time=0.137..0.148 rows=7 loops=9)
Recheck Cond: ((owner_member_id = dutm.id) AND (deadline IS NOT NULL) AND (deadline >= '2019-02-03 00:00:00+00'::timestamp with time zone) AND (deadline < '2019-04-15 00:00:00+00'::timestamp with time zone))
Heap Blocks: exact=36
-> BitmapAnd (cost=65.31..65.31 rows=1 width=0) (actual time=0.135..0.135 rows=0 loops=9)
-> Bitmap Index Scan on dhci_9adb17cb (cost=0.00..5.79 rows=182 width=0) (actual time=0.036..0.036 rows=167 loops=9)
Index Cond: (owner_member_id = dutm.id)
-> Bitmap Index Scan on dhci_deadline_ba8bd3addbfe7dc_uniq (cost=0.00..58.66 rows=2419 width=0) (actual time=0.263..0.263 rows=1727 loops=3)
Index Cond: ((deadline IS NOT NULL) AND (deadline >= '2019-02-03 00:00:00+00'::timestamp with time zone) AND (deadline < '2019-04-15 00:00:00+00'::timestamp with time zone))
-> Index Scan using wfciwf_pkey on wfciwf (cost=0.42..6.55 rows=1 width=13) (actual time=0.005..0.005 rows=1 loops=60)
Index Cond: (id = dhci.workflow_state_id)
Filter: (((current_status)::text <> 'killed'::text) AND ((current_status)::text <> 'parked'::text))
-> Index Scan using dhamti_d7bbcb82 on dhamti (cost=0.42..6.93 rows=2 width=8) (actual time=0.003..0.004 rows=1 loops=60)
Index Cond: (content_item_id = dhci.id)
-> Index Scan using dhcibs_6123fe8a on dhcibs (cost=0.29..1.10 rows=2 width=8) (actual time=0.003..0.005 rows=7 loops=60)
Index Cond: (ciid = dhci.id)
-> Index Scan using dhcit_6123fe8a on dhcit (cost=0.42..2.95 rows=2 width=8) (actual time=0.002..0.004 rows=9 loops=410)
Index Cond: (ciid = dhci.id)
-> Index Scan using ghcita_6123fe8a on ghcita (cost=0.42..3.07 rows=2 width=8) (actual time=0.002..0.003 rows=9 loops=3700)
Index Cond: (ciid = dhci.id)
-> Index Scan using dhcipc_6123fe8a on dhcipc (cost=0.29..1.41 rows=2 width=8) (actual time=0.001..0.002 rows=5 loops=33400)
Index Cond: (ciid = dhci.id)
-> Index Scan using dhcipt_6123fe8a on dhcipt (cost=0.29..1.49 rows=2 width=8) (actual time=0.001..0.001 rows=0 loops=172000)
Index Cond: (ciid = dhci.id)
-> Index Scan using dhcik_6123fe8a on dhcik (cost=0.29..1.41 rows=3 width=8) (actual time=0.001..0.001 rows=0 loops=172000)
Index Cond: (ciid = dhci.id)
Planning time: 8.219 ms
Execution time: 804.161 ms
(45 rows)