[postgis-users] Help me.

[Atul Kumar]

Hi Birgit,

Now its taking less time as compare to previous one.

One more help.

Is there any way to optimize this query because its also taking long time to execute.

select st_union (st_union (t1.geometry, t2.geometry), t3.geometry) geometry from TEMP_OUTPUTTREE_2 t1,TEMP_OUTPUTTREE2_4 t2, TEMP_OUTPUTTREE_5 t3

Thanks
Atul


From: postgis-users-bounces at postgis.refractions.net [mailto:postgis-users-bounces at postgis.refractions.net] On Behalf Of Birgit Laggner
Sent: Wednesday, November 23, 2011 6:07 PM
To: postgis-users at postgis.refractions.net
Subject: Re: [postgis-users] Help me.

Hallo Atul,

perhaps, I would split the query in two queries, because otherwise I think it might be difficult to use a spatial index on the second intersection. The queries could be like this:

--create a spatial index on each input table:
create index temp_outputtree_2_gist_geometry on temp_outputtree_2 using gist(geometry);
create index temp_outputtree2_4_gist_geometry on temp_outputtree2_4 using gist(geometry);
create index temp_outputtree_5_gist_geometry on temp_outputtree_5 using gist(geometry);

--intersection of the first 2 tables using the spatial index, writing the result of it into a new table:
select st_intersection(t1.geometry,t2.geometry) as geometry into new_table from TEMP_OUTPUTTREE_2 t1 inner join TEMP_OUTPUTTREE2_4 t2 on t1.geometry && t2.geometry where st_intersects(t1.geometry,t2.geometry);

--create a spatial index on the new geometries of the first intersection:
create index new_table_gist_geometry on new_table using gist(geometry);

--intersection with the third table:
select st_intersection(nt.geometry,t3.geometry) as geometry from new_table nt inner join TEMP_OUTPUTTREE_5 t3 on nt.geometry && t3.geometry where st_intersects(nt.geometry,t3.geometry);

Hope that helps,

Birgit.

Am 23.11.2011 13:16, schrieb Atul Kumar:
Hi All,

I am trying  to intersection multiple sets of  geographical data using ST_intersection function. But query execution time is long.
My Query is :
select st_intersection (st_intersection (t1.geometry, t2.geometry), t3.geometry) geometry from TEMP_OUTPUTTREE_2 t1,TEMP_OUTPUTTREE2_4 t2, TEMP_OUTPUTTREE_5 t3

I am having three table its having geometry data. I want to intersect operation on those data.

Please suggest, Is there any optimal way to get the intersection with less execution time?

Thanks
Atul Kumar


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