Re: Planner estimates cost of 'like' a lot lower than '='??

From: Buddy Lee Haystack <haystack(at)email(dot)rentzone(dot)org>
To: Mats Lofkvist <mal(at)algonet(dot)se>
Cc: pgsql-general(at)postgresql(dot)org
Subject: Re: Planner estimates cost of 'like' a lot lower than '='??
Date: 2001-07-22 13:50:30
Message-ID: 3B5ADA26.BF5FF52@email.rentzone.org
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Mats Lofkvist wrote:
>
> I have a multiple-join select that takes ~70 seconds to execute
> but if I remove one of the indexes the time drops to ~2 seconds.
>
> _
> Mats Lofkvist
> mal(at)algonet(dot)se
>

I ran into a similar problem on RedHat Linux v6.1 on Intel, kernel
2.2.12-20, PostgreSQL 6.5.3 when moving a system from a single processor
development box over to a dual processor production server. Dropping one
of the indexes on a lookup table with roughly 68,000 records on the
production box resulted in roughly a 3 fold increase in query execution
speed. At the time, I thought it was an SMP issue, and have since been
extremely conservative in adding indexes on SMP boxes.

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