Re: Proposed patch to make mergejoin cost estimation more symmetric - Mailing list pgsql-patches

From Alvaro Herrera
Subject Re: Proposed patch to make mergejoin cost estimation more symmetric
Date
Msg-id 20071207145749.GC5192@alvh.no-ip.org
Whole thread Raw
In response to Re: Proposed patch to make mergejoin cost estimation more symmetric  (Tom Lane <tgl@sss.pgh.pa.us>)
Responses Re: Proposed patch to make mergejoin cost estimation more symmetric
List pgsql-patches
Tom Lane wrote:
> Simon Riggs <simon@2ndquadrant.com> writes:
> > I do have a longer term issue that there is no information provided by
> > EXPLAIN to allow us to differentiate these two conditions.
>
> Sure there is: the new startup condition affects the estimated plan
> startup cost (only) and the existing termination condition affects the
> estimated total cost (only).

Yes, but how can you tell by looking at the explain?  I think the point
is that the "fraction that would be skipped" should be reported somehow.

--
Alvaro Herrera                  http://www.amazon.com/gp/registry/5ZYLFMCVHXC
Criptografía: Poderosa técnica algorítmica de codificación que es
empleada en la creación de manuales de computadores.

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