[postgis-users] St_union with group by faster

[Guillaume ARNAUD (ancienne adresse)]

Hi all, 

 I have a table in postgis which contains 6304 polygons.


I need to make a view which union some of this polygon.

 I write this
request :

 SELECT champ1, champ2,
st_multi(st_union(geom))::geometry(MULTIPOLYGON, 2154) geom
 FROM table

GROUP BY champ1, champ2, champ3, champ4, champ5

 The request works 36
seconds and give me the results.

 I have created some index on champ1
and champ2.

 Have you a tip to get the request faster ?

Thanks 
--


Guillaume ARNAUD
 Cellule SIGD
 Direction de l'Informatique
 Conseil
Départemental de Tarn-et-Garonne 
 
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