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Re: [9.2devel] why it doesn't do index scan only? - Mailing list pgsql-general

From Tom Lane
Subject Re: [9.2devel] why it doesn't do index scan only?
Date
Msg-id 11589.1318092466@sss.pgh.pa.us
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In response to [9.2devel] why it doesn't do index scan only?  (hubert depesz lubaczewski <depesz@depesz.com>)
Responses Re: [9.2devel] why it doesn't do index scan only?  (Tom Lane <tgl@sss.pgh.pa.us>)
Re: [9.2devel] why it doesn't do index scan only?  (Pavel Stehule <pavel.stehule@gmail.com>)
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hubert depesz lubaczewski <depesz@depesz.com> writes:
> it is selecting 20 rows out of 30 million. why is it:
> 1. not using index only scan
> 2. not using even normal index scan?

It thinks the bitmap scan is cheaper.  Whether that's true or not is not
very clear, but nobody is claiming that the costing of index-only scans
is accurate yet.

            regards, tom lane

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