Re: [postgis-users] More details for errors
Hi again! Well, this is always the same problem, if I do linemerge(union()), I have to force multi to prevent errors. Then, simplifying to linestring seems to consume resources. On way, would to do a view which determine if the union would lead to a multi or a linestring. But I don't know how to achieve this. I have no idea either if this would also be greedy on resources. Denis On 03/27/2012 05:43 PM, Nicolas Ribot wrote: Yes, it is 2.0 http://postgis.refractions.net/documentation/manual-svn/ST_CollectionHomogenize.html Well, I am turning around the problem... I have to do a cast, as I used ST_Multi(ST_LineMerge(ST_Union(wkb_geometry)))::geometry(MultiLineString,xxx) in the first view to prevent errors of unconnected lines. Right now the best solution I have is to let the view being unusable, and another view to report errors. This is not very satisfying as if a problem occurs, I cannot use my view until I fix the geometric errors. Basically, I need to compute a view with a LineMerge returning LineString (i.e. leaving away features leading to MultiLineString) and another view returning IDs of features leading to MULTI. I thought about using ST_Touches but it only uses two geometries and I can have more in the LineMerge. No idea what to look for... Thanks for your help. I could go deeper in the problem! Greetings I would then create 3 views: One doing the actual computation (linemerge(Union)), then one view where st_numgeometries(the_geom) = 1, and one view where st_numgeometries(the_geom) 1. nicolas ___ postgis-users mailing list postgis-users@postgis.refractions.net http://postgis.refractions.net/mailman/listinfo/postgis-users ___ postgis-users mailing list postgis-users@postgis.refractions.net http://postgis.refractions.net/mailman/listinfo/postgis-users
Re: [postgis-users] More details for errors
Hi Nicolas, hi all, Thanks for your reply. The problem is: - I cannot filter my view using where geometryType(wkb_geometry) = 'LINESTRING' as it will still return the same error - I cannot check the result of ST_LineMerge in the where clause since aggragates are not allowed in wheres - If I cast to a MULTI, I don't how to check that it is castable to a LineString. So, I'll try to reformulate: - Can I check if a MultiLineString is in fact a LineString ? - Is there a way to test the result of LineMerge to see if it is a LineString or MultiLineString? Thanks Denis On 03/26/2012 02:00 PM, Nicolas Ribot wrote: Hi all, I have a view which does this ST_LineMerge(ST_Union(wkb_geometry))::geometry(LineString,21781) In case of the lines are not juxtaposed, I have this error ERROR: Geometry type (MultiLineString) does not match column type (LineString) Is there a way of getting the line ID which leads to the error??? Hi, you could execute the SQL query defining the view and filter features where geometryType(wkb_geometry) = 'LINESTRING' to identify only problematic features. Nicolas ___ postgis-users mailing list postgis-users@postgis.refractions.net http://postgis.refractions.net/mailman/listinfo/postgis-users ___ postgis-users mailing list postgis-users@postgis.refractions.net http://postgis.refractions.net/mailman/listinfo/postgis-users
Re: [postgis-users] More details for errors
Hi Nicolas, Thanks again. Well, this working, but this not performant... Based on your suggestion, I tried this: in view1: ST_Multi(ST_LineMerge(ST_Union(wkb_geometry)))::geometry(MultiLineString,21781) AS wkb_geometry Then in view2: ST_CollectionHomogenize(wkb_geometry)::geometry(LineString,21781) AS wkb_geometry FROM view1 WHERE ST_NumGeometries(wkb_geometry) = 1; And I can detect problems by doing: SELECT id FROM view1 WHERE ST_NumGeometries(wkb_geometry) != 1; But this is slowing down a lot. I think that the ST_CollectionHomogenize is not the right way. Is there a better function to transform multiline to line if I am sure I only have lines? Greetings, Denis On 03/27/2012 02:29 PM, Nicolas Ribot wrote: On 27 March 2012 08:02, Denis Rouzauddenis.rouz...@gmail.com wrote: Hi Nicolas, hi all, Thanks for your reply. The problem is: - I cannot filter my view using where geometryType(wkb_geometry) = 'LINESTRING' as it will still return the same error - I cannot check the result of ST_LineMerge in the where clause since aggragates are not allowed in wheres - If I cast to a MULTI, I don't how to check that it is castable to a LineString. So, I'll try to reformulate: - Can I check if a MultiLineString is in fact a LineString ? - Is there a way to test the result of LineMerge to see if it is a LineString or MultiLineString? Hi, The number of elements in the collection will tell you if it is a linestring (1 element): st_numGeometries(), or the geometry type (geometryType() ) will start by 'MULTI' in case of collection. You could add a rule on your view to disallow st_lineMerge results producing MULTI elements. Nicolas ___ postgis-users mailing list postgis-users@postgis.refractions.net http://postgis.refractions.net/mailman/listinfo/postgis-users ___ postgis-users mailing list postgis-users@postgis.refractions.net http://postgis.refractions.net/mailman/listinfo/postgis-users
Re: [postgis-users] More details for errors
On 27 March 2012 16:09, Denis Rouzaud denis.rouz...@gmail.com wrote: Hi Nicolas, Thanks again. Well, this working, but this not performant... Based on your suggestion, I tried this: in view1: ST_Multi(ST_LineMerge(ST_Union(wkb_geometry)))::geometry(MultiLineString,21781) AS wkb_geometry Then in view2: ST_CollectionHomogenize(wkb_geometry)::geometry(LineString,21781) AS wkb_geometry FROM view1 WHERE ST_NumGeometries(wkb_geometry) = 1; And I can detect problems by doing: SELECT id FROM view1 WHERE ST_NumGeometries(wkb_geometry) != 1; But this is slowing down a lot. I think that the ST_CollectionHomogenize is not the right way. Is there a better function to transform multiline to line if I am sure I only have lines? I did not know this function. 2.0 ? You can simply do: st_setsrid(ST_geometryN(wkb_geometry), 21781) AS wkb_geometry FROM view1 WHERE ST_NumGeometries(wkb_geometry) = 1; If geoms come from linemerge, no need to cast to a linestring. It is already one. Nicolas ___ postgis-users mailing list postgis-users@postgis.refractions.net http://postgis.refractions.net/mailman/listinfo/postgis-users
Re: [postgis-users] More details for errors
Yes, it is 2.0 http://postgis.refractions.net/documentation/manual-svn/ST_CollectionHomogenize.html Well, I am turning around the problem... I have to do a cast, as I used ST_Multi(ST_LineMerge(ST_Union(wkb_geometry)))::geometry(MultiLineString,xxx) in the first view to prevent errors of unconnected lines. Right now the best solution I have is to let the view being unusable, and another view to report errors. This is not very satisfying as if a problem occurs, I cannot use my view until I fix the geometric errors. Basically, I need to compute a view with a LineMerge returning LineString (i.e. leaving away features leading to MultiLineString) and another view returning IDs of features leading to MULTI. I thought about using ST_Touches but it only uses two geometries and I can have more in the LineMerge. No idea what to look for... Thanks for your help. I could go deeper in the problem! Greetings Denis On 03/27/2012 04:39 PM, Nicolas Ribot wrote: On 27 March 2012 16:09, Denis Rouzauddenis.rouz...@gmail.com wrote: Hi Nicolas, Thanks again. Well, this working, but this not performant... Based on your suggestion, I tried this: in view1: ST_Multi(ST_LineMerge(ST_Union(wkb_geometry)))::geometry(MultiLineString,21781) AS wkb_geometry Then in view2: ST_CollectionHomogenize(wkb_geometry)::geometry(LineString,21781) AS wkb_geometry FROM view1 WHERE ST_NumGeometries(wkb_geometry) = 1; And I can detect problems by doing: SELECT id FROM view1 WHERE ST_NumGeometries(wkb_geometry) != 1; But this is slowing down a lot. I think that the ST_CollectionHomogenize is not the right way. Is there a better function to transform multiline to line if I am sure I only have lines? I did not know this function. 2.0 ? You can simply do: st_setsrid(ST_geometryN(wkb_geometry), 21781) AS wkb_geometry FROM view1 WHERE ST_NumGeometries(wkb_geometry) = 1; If geoms come from linemerge, no need to cast to a linestring. It is already one. Nicolas ___ postgis-users mailing list postgis-users@postgis.refractions.net http://postgis.refractions.net/mailman/listinfo/postgis-users ___ postgis-users mailing list postgis-users@postgis.refractions.net http://postgis.refractions.net/mailman/listinfo/postgis-users
Re: [postgis-users] More details for errors
Yes, it is 2.0 http://postgis.refractions.net/documentation/manual-svn/ST_CollectionHomogenize.html Well, I am turning around the problem... I have to do a cast, as I used ST_Multi(ST_LineMerge(ST_Union(wkb_geometry)))::geometry(MultiLineString,xxx) in the first view to prevent errors of unconnected lines. Right now the best solution I have is to let the view being unusable, and another view to report errors. This is not very satisfying as if a problem occurs, I cannot use my view until I fix the geometric errors. Basically, I need to compute a view with a LineMerge returning LineString (i.e. leaving away features leading to MultiLineString) and another view returning IDs of features leading to MULTI. I thought about using ST_Touches but it only uses two geometries and I can have more in the LineMerge. No idea what to look for... Thanks for your help. I could go deeper in the problem! Greetings I would then create 3 views: One doing the actual computation (linemerge(Union)), then one view where st_numgeometries(the_geom) = 1, and one view where st_numgeometries(the_geom) 1. nicolas ___ postgis-users mailing list postgis-users@postgis.refractions.net http://postgis.refractions.net/mailman/listinfo/postgis-users
[postgis-users] More details for errors
Hi all, I have a view which does this ST_LineMerge(ST_Union(wkb_geometry))::geometry(LineString,21781) In case of the lines are not juxtaposed, I have this error ERROR: Geometry type (MultiLineString) does not match column type (LineString) Is there a way of getting the line ID which leads to the error??? Thanks! Denis ___ postgis-users mailing list postgis-users@postgis.refractions.net http://postgis.refractions.net/mailman/listinfo/postgis-users
Re: [postgis-users] More details for errors
Hi all, I have a view which does this ST_LineMerge(ST_Union(wkb_geometry))::geometry(LineString,21781) In case of the lines are not juxtaposed, I have this error ERROR: Geometry type (MultiLineString) does not match column type (LineString) Is there a way of getting the line ID which leads to the error??? Hi, you could execute the SQL query defining the view and filter features where geometryType(wkb_geometry) = 'LINESTRING' to identify only problematic features. Nicolas ___ postgis-users mailing list postgis-users@postgis.refractions.net http://postgis.refractions.net/mailman/listinfo/postgis-users
