[postgis-users] Re: [PERFORM] Bad query optimizer misestimation because of TOAST

[strk at refractions.net]

On Fri, Feb 04, 2005 at 02:32:43PM +0100, Markus Schaber wrote:
> Hi, Strk,
> 
> strk at refractions.net schrieb:
> 
> > PostGIS always recheck, only to handle SRID consistency.
> > This is one of the problems Paul was ranting about in a previous
> > post ;). If no RECHECK is performed, queries using index
> > will not notice SRID mismatch, while those using a sequencial
> > scan will.
> 
> Was this the case for 0.X PostGIS, too?

Since 2004-03-08 (0.8.2).
--strk;

> > I wonder if dropping the RECHECK is another workaround for your
> > problem. Can you check it out ?
> 
> No. The problem was that the query planner was not using the index at
> all, thus forcing the load of all geometries during the sequential scan.
> 
> The lossiness of the index usually only causes very few false positives
> that have to be loaded for recheck, so I would regard this as a minor
> problem.
> 
> Markus
> 
> 
> --
> markus schaber | dipl. informatiker
> logi-track ag | rennweg 14-16 | ch 8001 zürich
> phone +41-43-888 62 52 | fax +41-43-888 62 53
> mailto:schabios at logi-track.com | www.logi-track.com
> 



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