[postgis-users] Query performance really slow..

[Marcelo Soares Souza]

Use EXPLAIN to show the execution plan of a statement, and post here.

  EXPLAIN  SELECT sum(st_area(ST_Intersection(bacini.geom,colture.geom))) as areacoltura, codice_bac, nome, codice_cor, colture.descrizione FROM drologia.bacini_elementari as bacini, (SELECT st_collect(geom) as geom, descrizione FROM varie.particellepac2006 group by 2) as colture group by 2,3,4,5;

March 13 2014 11:00 AM, "Pietro Rossin"  wrote: 

> Hi all
> I'm trying to query 2 vector layers;
> b) bacini_elementari that is river basins - 327 elements
> b) particellepac2006 colture parcels - 614000 elements
> 
> I want to intersect these two layers and get the sum of the area of each
> kind of colture for each river basin.
> To reduce the number of colture vectorial features I made a collect query
> (grouping by kind of colture) and I made a intersection between this
> geometry aggregation and all 327 basins.
> 
> My query is:
> 
> SELECT sum(st_area(ST_Intersection(bacini.geom,colture.geom))) as
> areacoltura, codice_bac, nome, codice_cor, colture.descrizione
> FROM idrologia.bacini_elementari as bacini,
> (SELECT st_collect(geom) as geom, descrizione
> FROM varie.particellepac2006
> group by 2) as colture
> group by 2,3,4,5
> 
> it's 5000000ms that the query is running and I don't have any result yet...
> 
> The two geometry column have an index (but I think it's not used in this
> query)
> 
> Mi pc id dual opteron with 4Gb RAM,
> "PostgreSQL 9.1.3, compiled by Visual C++ build 1500, 32-bit"
> 
> "POSTGIS="2.0.0 r9605" GEOS="3.3.3-CAPI-1.7.4" PROJ="Rel. 4.8.0, 6 March
> 2012" GDAL="GDAL 1.9.0, released 2011/12/29" LIBXML="2.7.8"
> LIBJSON="UNKNOWN" TOPOLOGY RASTER"
> 
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