[Qgis-user] Constraints on postgresql views

[Lionel Roubeyrie]

Hi all,
I try to construct views from a lines table to group roads' portions
together, but I fall on this view when called from QGIS :
SELECT 1::oid AS oid, ST_Multi(ST_Union(f.the_geom)) as the_geom
FROM (SELECT (ST_Dump(the_geom)).geom As the_geom FROM v_tmp) As f

but qgis says :
The view 'public.v_tmp2' has no column suitable for use as a unique key.
Qgis requires that the view has a column that can be used as a unique
key. Such a column should be derived from a table column of type int4
and be a primary key, have a unique constraint on it, or be a
PostgreSQL oid column. To improve performance the column should also
be indexed.
The view you selected has the following columns, none of which satisfy
the above conditions:
'the_geom' derives from 'public.tmp.the_geom' and is not suitable
(type is geometry) and does not have a suitable constraint)

thanks if someone can explain me why this doesn't work

-- 
Lionel Roubeyrie
lionel.roubeyrie at gmail.com
http://youarealegend.blogspot.com