[postgis-devel] CascadedUnion Early Results

[Kevin Neufeld]

That's impressive.  Good work Paul!
-- Kevin

Paul Ramsey wrote:
> For completeness, the whole table, about 4x faster:
> 
> uniontest=# select count(*) from counties;
>  count
> -------
>   3140
> (1 row)
> 
> uniontest=# select st_area(st_union(the_geom)) from counties;     st_area
> ------------------
>  1095.88034519544
> (1 row)
> 
> Time: 42352.399 ms
> 
> uniontest=# select st_area(st_union_fast(the_geom)) from counties;
>      st_area
> ------------------
>  1095.88034519544
> (1 row)
> 
> Time: 11493.832 ms
> 
> On Jan 20, 2009, at 1:11 PM, Paul Ramsey wrote:
> 
>> Looks good so far. Still chasing down an issue with GEOS before I can 
>> commit, but here's the current results:
>>
>>
>> uniontest=# select st_area(st_union(the_geom)) from counties where 
>> state_name = 'Texas';
>>     st_area
>> ------------------
>> 65.0596422159988
>> (1 row)
>>
>> Time: 702.491 ms
>>
>> uniontest=# select st_area(st_union_fast(the_geom)) from counties 
>> where state_name = 'Texas';
>>     st_area
>> ------------------
>> 65.0596422159988
>> (1 row)
>>
>> Time: 216.526 ms
>>
>> In the final commit there will just be one st_union() that does the 
>> right thing. I made two so I could do comparisons like the above more 
>> easily. Perhaps I should leave in a legacy st_union_slow() for people 
>> to compare with...
>>
>> -- 
>> Paul Ramsey
>> OpenGeo - http://opengeo.org
>> Putting the "Po" in "PostGIS".
>>
>> _______________________________________________
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>> http://postgis.refractions.net/mailman/listinfo/postgis-devel
> 
> 
> -- 
> Paul Ramsey
> pramsey at cleverelephant.ca
> +1 250 885 0632
> 
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