[GRASS-dev] postgresql speed

[Moritz Lennert]

On 03/03/09 22:17, Wouter Boasson wrote:
> In reply to Vincent's remarks on database interfaces:
> I don't know how the db.* modules are implemented, but I can't imagine that
> they process the data themselves. 

No, they use the underlying engine of the backend. But connection is 
costly. This is why scripts which had a loop calling [v.]db.* statements 
in each run of the loop should be rewritten to collect SQL statements in 
a temp file and then call db.execute once at the end. See [1] for the 
example of v.rast.stats.

See also some comments of Radim in [2] under "Attributes".

Moritz

[1]http://trac.osgeo.org/grass/changeset/20358
[2]http://freegis.org/cgi-bin/viewcvs.cgi/grass6/doc/vector/TODO?rev=HEAD&content-type=text/vnd.viewcvs-markup