[postgis-users] Point, Polygon - Does not intersects

[Hugues François]

Hello,
 
Maybe the issue is the number of polygon which not intersect between your tables : this query will return you all g1 polygon any times it does not intersect one polygon in your g2 table (I don't know if I'm clear enought, but a g1 polygon where g2 exists will also be returned since it does not intersect others g2 polygon)
 
I think you could try 
 
SELECT name, geom INTO gadm2_level1_union_selected
FROM 
(SELECT g1.*, g2.gid AS g2_gid FROM gadm2_level1_union g1
LEFT JOIN  gadm2_level2_union g2 ON ST_Intersects(g1.centroid, g2.geom)) foo
WHERE g2_gid is null
 
Hugues.
 

________________________________

From: postgis-users-bounces at lists.osgeo.org [mailto:postgis-users-bounces at lists.osgeo.org] On Behalf Of Andreas Forø Tollefsen
Sent: Monday, February 17, 2014 11:49 AM
To: PostGIS Users Discussion
Subject: [postgis-users] Point, Polygon - Does not intersects


Hi, 

I am running the current setup:
 "POSTGIS="2.0.2 r10789" GEOS="3.4.0dev-CAPI-1.8.0" PROJ="Rel. 4.7.1, 23 September 2009" GDAL="GDAL 1.9.0, released 2011/12/29" LIBXML="2.7.8" (core procs from "2.0.1 r9979" need upgrade) RASTER (raster procs from "2.0.1 r9979" need upgrade)"

I have two tables with geometries. Both include polygons representing administrative units. One at the first level and one at the second level.
I want a table that includes all the second level polygons where available, and where not available I want the first level polygons.

To find the level 1 polygons for filling the gaps where level 2 is N/A, I thought about finding where the centroid of level one polygons does not intersects with the polygons for level 2.

Hence, I tried:

SELECT g1.name, g1.geom INTO gadm2_level1_union_selected FROM gadm2_level1_union g1, gadm2_level2_union g2 WHERE ST_Intersects(g1.centroid, g2.geom)=FALSE;


I also tried the ST_Disjoint(g1.centroid, g2.geom).

My problem is that this is running for ages without finishing. This should be such a simple query, but I have used half of the day running it. If I take the two geometries into PostGIS and run a spatial query to find the points from level 1 not intersecting with polygons of level 2, it takes 15 seconds.

What could be the issue with my query?

Thanks!
Andreas

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