Hi Nicklas sr for the mistake ... field but it *was not* improve the perofrmance for ST_intersect
Cheers On Tue, May 25, 2010 at 3:53 PM, nguyen liem <[email protected]> wrote: > Hi Nicklas > > my dataset about 100.000 rows and after run my query i get about 15.000 > rows. I has created index for "geom" field but it was improve the > perofrmance for ST_intersect > > I used SRID 4326, but I don't know how to convert from degree to meter. > > Cheers > > On Tue, May 25, 2010 at 3:43 PM, Nicklas Avén > <[email protected]>wrote: > >> Ok >> >> The distance of 0.00001 degree in east west direction will vary depending >> on how far from the equator you are. >> >> How many points is there in your dataset? >> >> Do you see if the index is used? >> >> /Nicklas >> >> >> 2010-05-25 nguyen liem wrote: >> >> Hi Nicklas >> > >> >Actually the points can be outside the polygon and returning true but it >> can be tolerance about 1 meters outside. >> >I'm using SRID: 4326. I would like to know 0.00001 with the projection >> 4326 is equal 1 meter or not ? >> > >> >I used ST_Intersects (geom, geometry); but it's really slow, I don't know >> why. >> >I also used ST_Dwithin (geom, geometry, 0) and the result is empty, i >> couldn't found any neighbour. >> > >> >Cheers >> > >> >> >> On Tue, May 25, 2010 at 3:22 PM, Nicklas Avén <[email protected]> >> wrote: >> > > >> Hallo >> > >> > What you are doing with ST_Dwithin is to check if your geom and geometry >> have parts closer to (or exactly) 0.00001 mapunits from eachother. If you >> are using a meter based SRID then you are checking if they are within >> 0.00001 meters from eachother. So actually in this case your points can be >> just outside the polygon and returning true. If you want to use st_dwithin >> you should use 0 instead of 0.00001 . But I don't think that is any faster >> than ST_Intersects. The important thing in both cases is to have working >> spatial indexes. >> > >> > put an index on geom column in my_neighbour table and analyze the table. >> > >> > Create index idx_mn_geom >> > on my_neighbour >> > using gist(geom); >> > analyse my_neighbour; >> > >> > Then try:> >> >> > SELECT id, geom >> > FROM my_neighbour >> > >> WHERE ST_Intersects (geom, geometry); >> > >> > I guess that is the best solution. >> > >> > Hope that helps >> > >> > Nicklas> >> >> > >> > 2010-05-25 nguyen liem wrote: >> > >> > Hi all >> > > >> > >At the first time i used ST_Contains but it take a long time, so I used >> ST_Dwithin to improve the performance for the query statement but i don't >> know it is correct or not. >> > >I would like to know my points are within in polygon or not: >> > > >> > >SELECT id, geom >> > >FROM my_neighbour >> > >WHERE ST_Dwithin (geom, geometry, 0.00001) >> > > >> > >geometry: is a polygon(input parameter). >> > >0.00001: I means the radius of geometry is 1 meters, is it right? >> > > >> > > >> > >Cheers. >> > > >> > >-- >> > >Liem Nguyen >> > >Developer >> > >Axon Active Corp. >> > >> >---------------------------------------------------------------------------- >> > >Direct Line : +84 38 948 4645 >> > >Fax : +84 38 811 3489 >> > > Mobile Phone : +84 168 994 8897 >> > >Skype ID : liemnguyendl2204 >> > >Email : [email protected] / >> [email protected] >> > >> > Web Site : axonactive.vn> >> >> > >Address : 87 Thang Long Street,Gate 2 Ward 4, >> > > Tan Binh District, HCM city, Vietnam. >> > > >> > > >> >> >_______________________________________________ >> > postgis-users mailing list >> >[email protected] >> >postgis.refractions.net/mailman/listinfo/postgis-users >> > >> > >> >> > >> > >> >-- >> >Liem Nguyen >> >Developer >> >Axon Active Corp. >> >> >---------------------------------------------------------------------------- >> >Direct Line : +84 38 948 4645 >> > Fax : +84 38 811 3489 >> >Mobile Phone : +84 168 994 8897 >> >Skype ID : liemnguyendl2204 >> >Email : [email protected] / >> [email protected] >> > Web Site : axonactive.vn >> >Address : 87 Thang Long Street,Gate 2 Ward 4, >> > Tan Binh District, HCM city, Vietnam. >> > >> > >> >> _______________________________________________ >> postgis-users mailing list >> [email protected] >> http://postgis.refractions.net/mailman/listinfo/postgis-users >> >> > > > -- > Liem Nguyen > Developer > Axon Active Corp. > > ---------------------------------------------------------------------------- > Direct Line : +84 38 948 4645 > Fax : +84 38 811 3489 > Mobile Phone : +84 168 994 8897 > Skype ID : liemnguyendl2204 > Email : [email protected] / [email protected] > Web Site : http://axonactive.vn > > Address : 87 Thang Long Street,Gate 2 Ward 4, > Tan Binh District, HCM city, Vietnam. > > -- Liem Nguyen Developer Axon Active Corp. ---------------------------------------------------------------------------- Direct Line : +84 38 948 4645 Fax : +84 38 811 3489 Mobile Phone : +84 168 994 8897 Skype ID : liemnguyendl2204 Email : [email protected] / [email protected] Web Site : http://axonactive.vn Address : 87 Thang Long Street,Gate 2 Ward 4, Tan Binh District, HCM city, Vietnam.
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