[postgis-users] Query performance really slow..

[Pietro Rossin]

"GroupAggregate  (cost=324001.58..329989.92 rows=21516 width=28454)"
"  ->  Sort  (cost=324001.58..324055.53 rows=21582 width=28454)"
"        Sort Key: bacini.codice_bac, bacini.nome, bacini.codice_cor,
particellepac2006.descrizione"
"        ->  Nested Loop  (cost=59426.24..59835.94 rows=21582 width=28454)"
"              ->  Seq Scan on bacini_elementari bacini  (cost=0.00..138.27
rows=327 width=28397)"
"              ->  Materialize  (cost=59426.24..59428.06 rows=66 width=57)"
"                    ->  HashAggregate  (cost=59426.24..59427.07 rows=66
width=1169)"
"                          ->  Seq Scan on particellepac2006
(cost=0.00..56355.83 rows=614083 width=1169)"
Thanks!


2014-03-13 15:15 GMT+01:00 Marcelo Soares Souza [via PostGIS] <
ml-node+s17n5005873h87 at n6.nabble.com>:

> 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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