[postgis-users] help optimize distance calculation

[Sky]

Mmm, yes... great idea. I'll try that in the morning.

Sky

On Tue, Jan 27, 2009 at 7:16 PM, Paul Ramsey <pramsey at opengeo.org> wrote:
> Is there a maximum expected mindistance?
>
> select min(distance(f.the_geom,g.the_geom)) from features f, grid g
> where st_dwithin(f,g,[maxmindistance]) group by ao.gid
>
> P.
>
> On Tue, Jan 27, 2009 at 3:56 PM, Sky <shlyon+postgis at gmail.com> wrote:
>> Hello all, I'm new to postgis and I'm hoping someone might help advise me!
>>
>> I have a 4 million point grid of lat lon pairs that have an associated
>> the_geom. I have a 2,000 point feature set with an associated
>> the_geom. I'd like to find the nearest feature to each grid point. I
>> wrote the statement: select min(distance(f.the_geom,g.the_geom)) from
>> features f, grid g group by ao.gid to obtain my desired result set.
>> The only problem I had is that this query took 9949764 ms (approx 2.5
>> hours). Granted it's a large dataset, but I'd like to believe that
>> this calculation can be done more quickly. Any tips??
>>
>> Thanks,
>> Sky
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