[postgis-users] Slow Postgres Query

[Emilie Laffray]

2009/10/1 dassouki <dassouki at gmail.com>

> / 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...

Emilie Laffray
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