Re: Surprised by index choice for count(*) - Mailing list pgsql-general

From Tom Lane
Subject Re: Surprised by index choice for count(*)
Date
Msg-id 31534.1525191072@sss.pgh.pa.us
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In response to Surprised by index choice for count(*)  (Rob Sargent <robjsargent@gmail.com>)
Responses Re: Surprised by index choice for count(*)  (Rob Sargent <robjsargent@gmail.com>)
List pgsql-general
Rob Sargent <robjsargent@gmail.com> writes:
> Should I be?  I would have thought the pk would have been chosen v. 
> function index?

If I'm reading this correctly, the PK index contains uuids while
the fpv index contains float4s, meaning the latter is probably half
the size.  So scanning it is a lot cheaper, at least according to
the planner's cost model.

            regards, tom lane


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