[postgis-users] functions

[tommaso]

Why do you do ST_AsText(e.geom)::geometry? This is equivalent to e.geom. 
Change the query so:
SELECT e.gid, e.geom FROM electric_line e, fuses f WHERE 
ST_DWithin(e.geom, f.geom 0.01) AND f.gid=$1 .....

No sure if it does help, but you you can also try so:
SELECT e.gid, e.geom FROM electric_line e JOIN fuses f ON 
ST_DWithin(e.geom, f.geom, 0.01) WHERE f.gid=$1

Also
WHERE ST_DWithin(ST_EndPoint(f.geom),ST_StartPoint(n.geom),0.01)
can be changed to:
WHERE ST_Distance(ST_EndPoint(f.geom),ST_StartPoint(n.geom)) <= 0.01
which should be faster.

Obviously you need a GIST index on booth geometry columns.

If it all does not help please attach some test data.

Cheers, Tommaso



On 12/10/2013 03:01 AM, Jonatan Malaver wrote:
>
> Another question, what can I do to improve performance on the query? 
> The query can take 2 seconds or more.
>
> *From:*postgis-users-bounces at lists.osgeo.org 
> [mailto:postgis-users-bounces at lists.osgeo.org] *On Behalf Of *Jonatan 
> Malaver
> *Sent:* Monday, December 09, 2013 8:52 PM
> *To:* PostGIS Users Discussion
> *Subject:* Re: [postgis-users] functions
>
> Thank you!!!
>
> Jon
>
> *From:*postgis-users-bounces at lists.osgeo.org 
> [mailto:postgis-users-bounces at lists.osgeo.org] *On Behalf Of *tommaso
> *Sent:* Monday, December 09, 2013 12:57 PM
> *To:* PostGIS Users Discussion
> *Subject:* Re: [postgis-users] functions
>
> This should work:
>
> create or replace function flow(integer) RETURNS TABLE (gid int, geom 
> geometry, geojson text) AS
> $$
>
> WITH RECURSIVE flow(gid, geom) AS (
>
>     SELECT e.gid, e.geom FROM electric_line e, fuses f WHERE 
> ST_DWithin(ST_AsText(e.geom)::geometry, ST_AsText(f.geom)::geometry, 
> 0.01) AND f.gid=$1
>
>   UNION ALL
>
>     SELECT n.gid, n.geom
>
>     FROM electric_line n, flow f
>
>     WHERE ST_DWithin(ST_EndPoint(f.geom),ST_StartPoint(n.geom),0.01)
>
>   )
>
> SELECT *, ST_ASGeoJSON(ST_Transform(geom,4326),6) AS geojson
>
> FROM flow;
>
>  $$
> LANGUAGE SQL;
>
>
> SELECT * FROM flow(1);
>
>
> On 12/09/2013 03:57 PM, Jonatan Malaver wrote:
>
>     Hello,
>
>       I'm new to postgis/postgresql. I was wondering if anyone could
>     tell me how to make a function out of this sql query:
>
>     WITH RECURSIVE flow(gid, geom) AS (
>
>         SELECT e.gid, e.geom FROM electric_line e, fuses f WHERE
>     ST_DWithin(ST_AsText(e.geom)::geometry,
>     ST_AsText(f.geom)::geometry, 0.01) AND f.gid=' . $_GET['fuse'] . '
>
>       UNION ALL
>
>         SELECT n.gid, n.geom
>
>         FROM electric_line n, flow f
>
>         WHERE ST_DWithin(ST_EndPoint(f.geom),ST_StartPoint(n.geom),0.01)
>
>       )
>
>     SELECT *, ST_ASGeoJSON(ST_Transform(geom,4326),6) AS geojson
>
>     FROM flow;
>
>        I'd like to make a function flow(gid)
>
>     Thanks,
>
>     Jon
>
>
>
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>
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