[postgis-users] merge geometries

[Heitzso]

thanks for the info

Paul Ramsey wrote:
> Now that we have GEOS functionality, we can bind the geomunion (man I 
> hate that namespace hack (stupid spec writers)) into an aggregate 
> function which does what you want. It will be necessarily slow (each 
> union will be done separately and serially) but it should provide the 
> kind of result people are looking for:
> 
> select geomunion(the_geom),tract_number from census data group by 
> tract_number
> 
> Would return one polygon (assuming spatial adjacency) for each 
> tract_number.
> 
> Paul