Re: two table join just not fast enough.

От: Mark Kirkwood
Тема: Re: two table join just not fast enough.
Дата: ,
Msg-id: 4EB1F2CF.9030304@catalyst.net.nz
(см: обсуждение, исходный текст)
Ответ на: two table join just not fast enough.  (Brian Fehrle)
Список: pgsql-performance

Скрыть дерево обсуждения

two table join just not fast enough.  (Brian Fehrle, )
 Re: two table join just not fast enough.  (Tom Lane, )
  Re: two table join just not fast enough.  (Brian Fehrle, )
 Re: two table join just not fast enough.  (Mark Kirkwood, )

On 03/11/11 09:12, Brian Fehrle wrote:
>
>
> And here is a query plan.
>
> Hash Join  (cost=17516.470..26386.660 rows=27624 width=4) (actual
> time=309.194..395.135 rows=12384 loops=1)
>     Hash Cond: (yankee.alpha = hotel_zulu.quebec)
>   ->   Bitmap Heap Scan on yankee  (cost=1066.470..8605.770 rows=27624
> width=20) (actual time=5.178..34.693 rows=26963 loops=1)
>           Recheck Cond: (mike = 402513)
>         ->   Bitmap Index Scan on hotel_alpha  (cost=0.000..1059.570
> rows=27624 width=0) (actual time=4.770..4.770 rows=26967 loops=1)
>                 Index Cond: (mike = 402513)
>   ->   Hash  (cost=14465.080..14465.080 rows=114154 width=16) (actual
> time=303.717..303.717 rows=129908 loops=1)
>           Buckets: 4096  Batches: 8  Memory Usage: 784kB
>         ->   Bitmap Heap Scan on hotel_zulu  (cost=2461.770..14465.080
> rows=114154 width=16) (actual time=25.642..185.253 rows=129908 loops=1)
>                 Recheck Cond: ((two)::golf = ANY ('xray'::golf[]))
>               ->   Bitmap Index Scan on kilo  (cost=0.000..2433.230
> rows=114154 width=0) (actual time=23.887..23.887 rows=130292 loops=1)
>                       Index Cond: ((two)::golf = ANY ('xray'::golf[]))
>

Might be worth posting table definitions, as this plan does not
immediately look like it came from the query you posted. Also unless I
am misreading the output looks like you have some custom datatypes (e.g
'golf'), so more info there could be useful too.

When we have that, there may be something to be learned from examining
the pg_stats data for the join and predicate columns used in these queries.

regards

Mark


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