v.out.ogr: don't use random access to find attributes

[neteler]

Moved here from ​http://trac.osgeo.org/grass/browser/grass/trunk/doc/vector/TODO#L250

Radim suggested:

v.out.ogr is very slow because it is using random access to the attributes. It should be rewritten so that all attributes are selected by one query, geometry for each attribute can be searched by category index (which is fast).

[mlennert]

Replying to neteler:

Moved here from ​http://trac.osgeo.org/grass/browser/grass/trunk/doc/vector/TODO#L250

Radim suggested:

v.out.ogr is very slow because it is using random access to the attributes. It should be rewritten so that all attributes are selected by one query, geometry for each attribute can be searched by category index (which is fast).

I've implemented something like this in a long-ago rewrite (never committed) of d.vect.chart [1] - see plot.c. It uses db_open_select_cursor to access the table in one query and then for each row Vect_cidx_find_all to find the geometries associated to the cat value in that row.

Moritz

[1] ​http://lists.osgeo.org/pipermail/grass-dev/2006-October/026624.html