Re: cost_index() and path row estimate. - Mailing list pgsql-hackers

From Bernd Helmle
Subject Re: cost_index() and path row estimate.
Date
Msg-id 6CA3F331D7D7697A9F03A4D1@eje.credativ.lan
Whole thread Raw
In response to Re: cost_index() and path row estimate.  (Tom Lane <tgl@sss.pgh.pa.us>)
List pgsql-hackers

--On 1. Mai 2015 11:30:51 -0700 Tom Lane <tgl@sss.pgh.pa.us> wrote:

> No.  The non-parameterized paths for a given relation must all have the
> same rowcount estimates; otherwise the path comparison logic fails
> fundamentally.  Another way to look at it is that every correct path
> will yield the same number of rows in reality; so it would be wrong to
> give a path that makes use of a partial index a rowcount advantage over
> a path that is not using the partial index but nonetheless is enforcing
> exactly the same set of scan restriction clauses.

Thanks for the explanation. 

-- 
Thanks
Bernd



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