[postgis-users] improving within()

[Paul Ramsey]

Fred's got it, listen to Fred!!!

(Never build a buffer if you don't need to.)

On Mon, Jun 29, 2009 at 9:16 AM, Fred Lehodey<lehodey at gmail.com> wrote:
> Hi Marco,
> ST_DWithin(geometry, geometry, float)
>
> Returns true if geometries are within the specified distance of one another.
> Uses indexes if available.
>
> HTH,
> Fred
>
>
>
>
> On Mon, Jun 29, 2009 at 4:46 PM, Marco Lechner - FOSSGIS e.V.
> <marco.lechner at fossgis.de> wrote:
>>
>> hi list,
>>
>> we are using within(geometry, geometry) to test if some (~1200) points
>> are within a polygon. the polygon is defined as buffer(linegeometry,
>> dist). the problem is, that the line is always the same and therefore
>> the result of buffer(linegeometry, dist)  is always the same. while
>> iterating through the points the within() calculates the
>> buffer(linegeometry) each time again. the function takes 40s. instead of
>> 0.04s if i calculate the buffergeometry first and use it as "fixed
>> geometry" at within() - is this somehow improvable (within() recognizing
>> such a behaviour?, ...)?
>>
>> Marco
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>
>
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