Re: index usage on queries on inherited tables - Mailing list pgsql-performance

From Joseph Shraibman
Subject Re: index usage on queries on inherited tables
Date
Msg-id 4DB88690.5050701@selectacast.net
Whole thread Raw
In response to Re: index usage on queries on inherited tables  (Robert Haas <robertmhaas@gmail.com>)
Responses Re: index usage on queries on inherited tables  (Samuel Gendler <sgendler@ideasculptor.com>)
Re: index usage on queries on inherited tables  (Greg Smith <greg@2ndquadrant.com>)
Re: index usage on queries on inherited tables  (Robert Haas <robertmhaas@gmail.com>)
List pgsql-performance
On 04/27/2011 04:32 PM, Robert Haas wrote:
> In the first case, PostgreSQL evidently thinks that using the indexes
> will be slower than just ignoring them.  You could find out whether
> it's right by trying it with enable_seqscan=off.

My point is that this is just a problem with inherited tables.  It
should be obvious to postgres that few rows are being returned, but in
the inherited tables case it doesn't use indexes.  This was just an
example.  In a 52 gig table I have a "select id from table limit 1 order
by id desc" returns instantly, but as soon as you declare a child table
it tries to seq scan all the tables.

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