[postgis-devel] What's the point of this exercise in intersects?

[Obe, Regina]

You guys are going to hate me.  My C'est La Vie was short-lived.  It just occurred to me
unless my understanding of how PostgreSQL and PostGIS works is wrong.

Even if you don't have indexes on your geometry isn't the implicit

&& going to force a bounding box check still and since operators have higher priority, wouldn't that still be run before the 
_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? 

Explain that to me Mark and perhaps I can be blissful again.

Thanks,
Regina

-----Original Message-----
From: postgis-devel-bounces at postgis.refractions.net on behalf of Obe, Regina
Sent: Mon 9/8/2008 8:00 PM
To: PostGIS Development Discussion
Subject: RE: [postgis-devel] What's the point of this exercise in intersects?
 

> There are cases where the geometry is generated within the query, such
> as by buffering and the like, where an index cannot be created.  There
> are cases where a sequence scan is selected by the scheduler for
> whatever reason (selectivity of other constraints, size of table,
> outdated stats...).  And there's the case where the user didn't build an
> index.  Given the low overhead these shortcuts introduce, I would prefer
> to leave them in order to cover these sorts of cases.

--
> Mark Leslie

Thanks Mark - Now I feel C'est la vie too :)

Regina


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