[GRASS-dev] Speeding up v.out.ogr (again)

[Benjamin Ducke]

Dear Devs,

A while ago, I submitted a small patch for v.out.ogr
that moves the SQL SELECT out of the mk_att() function,
so that this costly operation does not have to be
performed multiple times:

http://lists.osgeo.org/pipermail/grass-dev/2011-January/053150.html

Looking at 6.4.2 and 6.5 SVN copies of v.out.ogr,
I see that SQL SELECT is still (again?) in mk_att(), with
this comment (line 1053):

  /* Fetch all attribute records for cat <cat> */ 
  /* opening and closing the cursor is slow, 
   * but the cursor really needs to be opened for each cat separately */

Is this because of GRASS maps that have more than one
attribute table connection?

If so, then I suggest putting in a condition, so that those
GRASS maps that have just one attribute table can perform
the SQL SELECT outside of mk_att(). Otherwise, we punish
all GRASS users with extremely slow export speed, even though
most of them might not even use multi-table attributes in
their projects. The difference in my test was something like
factor 500!

Best,

Ben

-- 
Benjamin Ducke
{*} Geospatial Consultant
{*} GIS Developer
  
  benducke AT fastmail.fm