Re: Subquery WHERE IN or WHERE EXISTS faster?

"Ulrich" <ulrich(dot)mierendorff(at)gmx(dot)net> writes:

> EXPLAIN ANALYZE SELECT speed FROM processors WHERE id IN (SELECT processorid
> FROM users_processors WHERE userid=4040) ORDER BY speed ASC LIMIT 10 OFFSET 1;
>
> Limit (cost=113.73..113.75 rows=7 width=5) (actual time=0.335..0.340 rows=10 loops=1)
> -> Sort (cost=113.73..113.75 rows=8 width=5) (actual time=0.332..0.333 rows=11 loops=1)

^^

> Sort Key: processors.speed
> Sort Method: quicksort Memory: 17kB
> -> Nested Loop (cost=47.22..113.61 rows=8 width=5) (actual time=0.171..0.271 rows=13 loops=1)
> -> HashAggregate (cost=47.22..47.30 rows=8 width=4) (actual time=0.148..0.154 rows=13 loops=1)
> -> Bitmap Heap Scan on users_processors (cost=4.36..47.19 rows=12 width=4) (actual time=0.074..0.117 rows=13 loops=1)

^^

> Index Cond: (userid = 4040)
> -> Index Scan using processors_pkey on processors (cost=0.00..8.28 rows=1 width=9) (actual time=0.006..0.007 rows=1 loops=13)
> Index Cond: (processors.id = users_processors.processorid)

It looks to me like you have some processors which appear in
"users_processors" but not in "processors". I don't know your data model but
that sounds like broken referential integrity to me.

--
Gregory Stark
EnterpriseDB http://www.enterprisedb.com
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