[postgis-users] linestring aggregation

Nicolas Gillet - MARKET-IP nicolas.gillet at market-ip.com
Tue Dec 29 02:39:32 PST 2009



I am trying to aggregate linestrings together based on their attributes and
the fact that they are touching each other.


Therefore I found out how to write a very basic aggregate function :


   CREATE AGGREGATE geometry_sum (

                SFUNC = st_union,

                BASETYPE = geometry,

                STYPE = geometry);


I can now aggregate my linestrings grouped by their names, importance, and
so on but . I have trouble to group them by the fact that they are touching
each other.


linestring A, B and C have the same attributes but only A and B are touching
each other.

I would like as a result A+B in one record, and C in a second record.


Does someone have any tips to share ?


Thank you,




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