Hi Gus,
There isn't a function to to that exactly, but you can accomplish it
easy enough by doing just what you said ... appending the startpoint to
the end of the linestring.
ie.
UPDATE my_lines SET geom = ST_AddPoint(geom, ST_StartPoint(geom));
SELECT isring(addpoint(geom, startpoint(geom)))
FROM (select 'LINESTRING(0 0, 0 1, 1 1, 1 0)'::geometry as geom) as foo
I suppose you could also run your lines through the snaptogrid function
to remove duplicate points ... just in case you added a startpoint to an
already closed ring.
Cheers,
Kevin
Gustavo Ces wrote:
Thanks Kevin,
I´ll try it later, because it seems dump gives something different
i expected, so some experimentation is required. By the way, I´m
trying a different approach and i´ve got a question. After searching
in postgis list and manual, i can´t find a postgis function to close
an open linestring. So i supose have to add the first point as the
last one in my not very complex polygons. No problem. But my question
is, is there any other way? I think this type of job is very usual
(Arcgis, Cad software has functions to do it), so i´ts strange all
postgis folks write a large sentence to solve this... Is there any
Postgis function or postgis trick?
Maybe this mail is linked to another ones, talking about "reinventing
the wheel"? :)
Gus
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