[GRASS5] [bug #4075] (grass) grass and postgis issue
Kirk R. Wythers
kwythers at umn.edu
Fri Feb 10 09:38:31 EST 2006
On Feb 9, 2006, at 2:50 PM, Moritz Lennert wrote:
> So, if you import into GRASS vector format, the geometry is stored
> in the
> GRASS format, even if the data is in a postgres table (geometry and
> are handled separately in GRASS. This means that it is no longer a
> vector layer, but a GRASS vector layer. Postgis columns in the
> table or
> spatial indices will have no impact as the geometry is not in
This may be a silly question... but what then, is the point of
building GRASS with postgis support? If postgis is really only an
extension that adds geometry column and spatial indexing options to
postgresql, and GRASS does not use the posgis geometry, then why
bother with postgis?
Perhaps the answer to my question is that I do see a speed up with
spatial queries run from GRASS through db.execute (or when I run them
on the database with postgreql). You were right btw Moritz, the slow
response to the command d.vect seems to be at due to the time it
takes d.vect to 'draw'. The same query run in postgis is quite fast.
Also, if I make the query more selective so that fewer data points
get returned. d.vect returns faster (I think because there is less to
draw). Does that make sense to you?
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