Hello, 

I think this is consistent to have a homogeneous geometry type since a 
linestring could intersect numerous polygons of a multipolygon. Did you tried 
the st_dump function on the resulting st_multilinestring ? 

(st_dump(multilinestring)).geom will return the different linestrings which 
compose the multi ones. 

Regards, 

Hugues 



De: "Hemant Bist" <[email protected]> 
À: "PostGIS Users Discussion" <[email protected]> 
Envoyé: Mercredi 12 Avril 2017 21:14:07 
Objet: [postgis-users] ST_intersection converting st_linestring to 
st_multilinestring 

Hi, 
I am trying to figure out if this is expected behavior, or I am running into 
some bug / misinterpreting results. 

I am doing st_intersection(st_linestring, st_multipolygon). This is latlon 
geometry(EPSG:4326). The multiploygon is actually a polygon (with only one 
polygon in multipolygon) 

When I view the results as KML the intersection look correct, but the problem I 
see is that the resulting linestrings are unnecessarily getting split in 
mulilinestring. 

1) Every linestring is converted to multilinestring resulting in large nubmer 
of st_numgeomtries for each multilinestring. (even when the linestring is 
contained in polygon) 
2) ST_LineMerge on the resulting multilinestring does help but its far from 
"perfect" e.g. if the linestring is contained in polygon I expected the result 
to be one linesting, but the result of st_numgeometries() is more than 50. 

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