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<TITLE>RE: [postgis-devel] What's the point of this exercise in intersects?</TITLE>
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<P><FONT SIZE=2>You guys are going to hate me. My C'est La Vie was short-lived. It just occurred to me<BR>
unless my understanding of how PostgreSQL and PostGIS works is wrong.<BR>
<BR>
Even if you don't have indexes on your geometry isn't the implicit<BR>
<BR>
&& going to force a bounding box check still and since operators have higher priority, wouldn't that still be run before the<BR>
_ST_Intersects etc. The check in intersects etc. doesn't even work if there is no bounding box around the geometry, does a on the fly buffer ever have a bounding box?<BR>
<BR>
Explain that to me Mark and perhaps I can be blissful again.<BR>
<BR>
Thanks,<BR>
Regina<BR>
<BR>
-----Original Message-----<BR>
From: postgis-devel-bounces@postgis.refractions.net on behalf of Obe, Regina<BR>
Sent: Mon 9/8/2008 8:00 PM<BR>
To: PostGIS Development Discussion<BR>
Subject: RE: [postgis-devel] What's the point of this exercise in intersects?<BR>
<BR>
<BR>
> There are cases where the geometry is generated within the query, such<BR>
> as by buffering and the like, where an index cannot be created. There<BR>
> are cases where a sequence scan is selected by the scheduler for<BR>
> whatever reason (selectivity of other constraints, size of table,<BR>
> outdated stats...). And there's the case where the user didn't build an<BR>
> index. Given the low overhead these shortcuts introduce, I would prefer<BR>
> to leave them in order to cover these sorts of cases.<BR>
<BR>
--<BR>
> Mark Leslie<BR>
<BR>
Thanks Mark - Now I feel C'est la vie too :)<BR>
<BR>
Regina<BR>
<BR>
<BR>
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