Ben,
> INSERT INTO gis_roads (country, origin, name, roadtype, the_geom)
> SELECT 'KH', 'MU', userid, code, wkb_geometry FROM gis_roadsk order by
> centroid(wkb_geometry);
>
> and got this message back :
>
> ERROR: new row for relation "gis_roads" violates check constraint
> "enforce_geotype_the_geom"
Grab the definition of this CHECK constraint by clicking on the table in
pgAdminIII. Then do this:
ALTER TABLE gis_roads DROP CONSTRAINT enforce_geotype_the_geom;
ALTER TABLE gis_roads ADD CONTRAINT enforce_geotype_geom CHECK
(geometrytype(the_geom) IN ('LINESTRING'::text,'MULTILINESTRING'::text) OR
gethe_geomom IS NULL);
It will now allow linestrings and multilinestrings to be inserted into the
table.
> 1. Is there any reason I shouldn't use the GEOMETRY type for my
> aggregate table? (There must be or there wouldn't be any other types)
No
> 2. is ST_Multi() the best function to use to import them?
Well, I would change the defintiion of the enforce_geotype_geom CHECK
constraint and then import the data from the shapefiles regardless as to type.
Then you could fix any wrongly typed MULTILINESTRING geometries (ie those made
up of a single geometry) as follows:
UPDATE gis_roads
SET the_geom = ST_GeometryN(the_geom, 1)
WHERE the_geom is not null
AND ST_NumGeometries(the_geom) = 1;
Then, you can check if there are any multilinestring geometries in your table
as follows:
SELECT distinct GeometryType(the_geom) FROM gis_roads;
If you get two rows then the correct enforce_geotype_geom CHECK constraint is
as above (ie two geometry types).
If you get one row then you can change your CHECK constraint to only allow that
geometry (or you might decide that the table should support two types anyway).
> 3. Is there any reason I wouldn't want to mix the two data types...
> are linestrings more efficiently handled etc.
I'm not an expert on the specifics of PostGIS but if the object is a linestring
then store and index it as a linestring and remove the additional handling
required to extract the linestring from the multilinestring for processing and
rendering. Has to be a little bit faster.
Hope this helps
S.
--
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