当查询中存在“ WHERE IN”时，为什么Postgis不应用索引？

Question

我们有一个表shops，其列名为location的列GEOMETRY(POINT,4326)和类型为version的tinyint和一张桌子version，其中一行包含整数。

为什么下面的查询未使用GIST（位置）的索引？

SELECT * FROM shops 
WHERE ("version" IN (SELECT "version" FROM "version")) 
ORDER BY (location <-> '0020000001000010e64029d460d2a8aee0404bc8bb0955ea17'::geometry) LIMIT 10;

与没有IN的同一查询一样，does使用索引？

SELECT * FROM shops 
WHERE ("version" = (SELECT "version" FROM "version" LIMIT 1)) 
ORDER BY (location <-> '0020000001000010e64029d460d2a8aee0404bc8bb0955ea17'::geometry) LIMIT 10;

这影响了我们，因为我们从Postgres 9更新到11。我能够追溯到上面的选择。

编辑：添加qry分析

第一次查询（无索引应用程序：）>

"Limit  (cost=25260.30..25260.32 rows=10 width=1275) (actual time=254.809..254.814 rows=10 loops=1)"
"  ->  Sort  (cost=25260.30..25260.39 rows=36 width=1275) (actual time=254.807..254.809 rows=10 loops=1)"
"        Sort Key: ((shops.location <-> '0101000020E6100000E0AEA8D260D4294017EA5509BBC84B40'::geometry))"
"        Sort Method: top-N heapsort  Memory: 54kB"
"        ->  Nested Loop  (cost=41.88..25259.52 rows=36 width=1275) (actual time=0.099..215.201 rows=58179 loops=1)"
"              Join Filter: (shops.version = version.version)"
"              ->  HashAggregate  (cost=41.88..43.88 rows=200 width=4) (actual time=0.014..0.016 rows=1 loops=1)"
"                    Group Key: version.version"
"                    ->  Seq Scan on version  (cost=0.00..35.50 rows=2550 width=4) (actual time=0.009..0.010 rows=1 loops=1)"
第二个查询：

"Limit  (cost=0.28..440.04 rows=10 width=1275) (actual time=0.194..0.233 rows=10 loops=1)"
"  ->  Nested Loop Semi Join  (cost=0.28..1574995.44 rows=35815 width=1275) (actual time=0.193..0.230 rows=10 loops=1)"
"        Join Filter: (shop.version = version.version)"
"        ->  Index Scan using shop_location_idx on shops  (cost=0.28..101549.81 rows=71630 width=1267) (actual time=0.182..0.213 rows=10 loops=1)"
"              Order By: (location <-> '0101000020E6100000E0AEA8D260D4294017EA5509BBC84B40'::geometry)"
"        ->  Materialize  (cost=0.00..48.25 rows=2550 width=4) (actual time=0.001..0.001 rows=1 loops=10)"
"              ->  Seq Scan on version  (cost=0.00..35.50 rows=2550 width=4) (actual time=0.006..0.006 rows=1 loops=1)"
已解决

感谢@JimJones和@JimMacaulay，请参阅下面的答案

[我们有一个桌子商店，其列名为GEOMETRY（POINT，4326）类型的位置和tinyint类型的版本，以及带有一行包含整数的表版本。为什么下面的查询不使用...

Answer 1

以某种方式在版本表上添加索引也有助于Postgres使用location列上的索引。