[postgis-users] ST_intersection converting st_linestring to st_multilinestring

Hemant Bist hemantbist at gmail.com
Wed Apr 12 12:14:07 PDT 2017

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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