[GENERAL] PostGIS return multiple points

[trevor1940]

Hi

I have a PostGIS table and I wish to get the location/name of multiple
points at once the command for selecting one point is

select PolyName from MyPolygones where st_Contains(the_geom,
GeomFromText('point($LAT $LONG)4326');

where $LAT $LONG are perl varables
So how can i do this if iI have 100 points without hitting the database 100
times?

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Re: [GENERAL] PostGIS return multiple points

[maarten]

hey,

I haven't used postgis yet, however,

assuming the normal rules still apply and st_Contains returns
true/false:

SELECT ... WHERE st_Contains(point1) OR st_Contains(point2) OR ...

or using the IN statement:
SELECT ... WHERE true IN (st_Contains(point1),st_Contains(point2),...)

That should give you a list of all polynames.
The trick is figuring out what polyname goes with which point.  But I
leave that as an exercise to the reader, as it's tea time.

regards,
Maarten

On Thu, 2010-10-28 at 01:00 -0700, trevor1940 wrote:
 Hi
 
 I have a PostGIS table and I wish to get the location/name of multiple
 points at once the command for selecting one point is
 
 select PolyName from MyPolygones where st_Contains(the_geom,
 GeomFromText('point($LAT $LONG)4326');
 
 where $LAT $LONG are perl varables
 So how can i do this if iI have 100 points without hitting the database 100
 times?
 
 -- 
 View this message in context: 
 http://postgresql.1045698.n5.nabble.com/PostGIS-return-multiple-points-tp3240107p3240107.html
 Sent from the PostgreSQL - general mailing list archive at Nabble.com.
 


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Re: [GENERAL] PostGIS return multiple points

[ludwig]

Just some thoughts:
- create a multipoint with 100 vertices instead of a single point and query 
once with st_Intersect
- prepare the single-point-query and execute the prepared query 100 times with 
the changing coordinates

Ludwig 


- Ursprüngliche Nachricht -
Von: trevor1940
Gesendet: 28.10.10 10:00 Uhr
An: pgsql-general@postgresql.org
Betreff: [GENERAL] PostGIS return multiple points

Hi I have a PostGIS table and I wish to get the location/name of multiple 
points at once the command for selecting one point is select PolyName from 
MyPolygones where st_Contains(the_geom, GeomFromText('point($LAT $LONG)4326'); 
where $LAT $LONG are perl varables So how can i do this if iI have 100 points 
without hitting the database 100 times? -- View this message in context: 
http://postgresql.1045698.n5.nabble.com/PostGIS-return-multiple-points-tp3240107p3240107.html
 Sent from the PostgreSQL - general mailing list archive at Nabble.com. -- Sent 
via pgsql-general mailing list (pgsql-general@postgresql.org) To make changes 
to your subscription: http://www.postgresql.org/mailpref/pgsql-general

Re: [GENERAL] PostGIS return multiple points

[Szymon Guz]

On 28 October 2010 10:00, trevor1940 anto...@nsom.org.uk wrote:


 Hi

 I have a PostGIS table and I wish to get the location/name of multiple
 points at once the command for selecting one point is

 select PolyName from MyPolygones where st_Contains(the_geom,
 GeomFromText('point($LAT $LONG)4326');

 where $LAT $LONG are perl varables
 So how can i do this if iI have 100 points without hitting the database 100
 times?


hi,
Hi,
you could create one query using MULTIPOINT, something like:

ST_MPointFromText('MULTIPOINT($LAT1 $LONG1, $LAT2 $LONG2 ... $LAT100
$LONG100 )', 4326)

now you could find all polygons:

SELECT DISTINCT PolyName
FROM MyPolygones
WHERE ST_INTERSECTS(the_geom,
ST_MPointFromText('MULTIPOINT($LAT1 $LONG1, $LAT2 $LONG2 ... $LAT100
$LONG100 )', 4326)
);

where:
ST_INTERSECTS returns true if geometries have any common point
ST_MPointFromText creates brand new and shiny new MULTIPOINT geometry
containing all the points

regards
Szymon