Emilie Laffray wrote:
2009/10/1 dassouki <[email protected] <mailto:[email protected]>>
/ Hey All,
/>>/
/>>/ As some of you know, I've been trying to connect a point from
a point table
/>>/ to the projection of that point on the nearest line for close
to forever
/>>/ now.
/>>/
/>>/ I've managed to get the code working for a small set of
points and lines;
/>>/ however, on a 60 node with 2,000 lines, the query is in its
11th hour and
/>>/ still no sign of ending.
/>>/
/>>/ I posted a question including code on stack overflow
/>>/ http://stackoverflow.com/questions/1504353/slow-postgres-query
/>>/
/>>/ I was wondering if anyone here has any idea on what I might
be doing wrong
/>>/ ? and if there is a way to make the code more efficient
/>>/
/>>/
/> Hum, I am no expert but it looks like your 3000000 is way too
high.
I tried 1, 100, and 10000 and it didn't seem to speed up the query
Ok but what is your SRID? You have to pick a meaningful value based on
your SRID coordinates, with a reasonable amount of slices. It takes a
bit of trial of error to find the sweet spot for your dataset.
It depends a lot on the density of points etc...
I'm using SRID 32767 since the input prj file has the following proj:
PROJCS["NAD_1983_CSRS98_New_Brunswick_Stereographic",GEOGCS["GCS_North_American_1983_CSRS98",DATUM["D_North_American_1983_CSRS98",SPHEROID["GRS_1980",6378137.0,298.257222101]],PRIMEM["Greenwich",0.0],UNIT["Degree",0.0174532925199433]],PROJECTION["Double_Stereographic"],PARAMETER["False_Easting",2500000.0],PARAMETER["False_Northing",7500000.0],PARAMETER["Central_Meridian",-66.5],PARAMETER["Scale_Factor",0.999912],PARAMETER["Latitude_Of_Origin",46.5],UNIT["Meter",1.0]]
The area is about 150 sq km, i have roughly 90 nodes, and 2,100 lines
Emilie Laffray
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