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Re: Is this a planner bug? - Mailing list pgsql-general

From Pavel Stehule
Subject Re: Is this a planner bug?
Date
Msg-id CAFj8pRDkgSwRb6fx4N1k7n9gFqAResim+GDrxU1o9TUPw+0AkQ@mail.gmail.com
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In response to Is this a planner bug?  (Torsten Förtsch <torsten.foertsch@gmx.net>)
Responses Re: Is this a planner bug?  (Torsten Förtsch <torsten.foertsch@gmx.net>)
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Hello

what is your effective_cache_size in postgresql.conf?

What is random_page_cost and seq_page_cost?

Regards

Pavel

2014-04-22 14:10 GMT+02:00 Torsten Förtsch <torsten.foertsch@gmx.net>:
Hi,

I got this plan:

Limit  (cost=0.00..1.12 rows=1 width=0)
   ->  Seq Scan on fmb  (cost=0.00..6964734.35 rows=6237993 width=0)
         Filter: ...

The table has ~80,000,000 rows. So, the filter, according to the plan,
filters out >90% of the rows. Although the cost for the first row to
come out of the seqscan might be 0, the cost for the first row to pass
the filter and, hence, to hit the limit node is probably higher.

Thanks,
Torsten


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