[mapserver-users] WFS Layer running OGR Query Multiple timesperrequest

[Steve Lime]

It's particularly hard on the database backends because of the overhead of
running so many small queries. I should note that a true single pass query is
not easy to achieve. Many presentation methods, for example WFS/GML 
require a result set size at the start of a file which all but requires two 
passes over the data.  The most recent strategy involves two-passes but on
the same statement handle. At the recent code sprint we tested with Oracle
Spatial and PostGIS, both with significant improvements in performance. I'll
probably also add a small feature cache to avoid resetting the statement
handle in a majority of cases.

I'm not sure how the OGR driver will need to be updated though.

The sprint modifications are implemented in the MapServer sandbox:

  http://svn.osgeo.org/mapserver/sandbox/single-pass/mapserver/

Steve

>>> Frank Warmerdam <warmerdam at pobox.com> 03/31/09 8:32 PM >>>
Robert Sanson wrote:
> Sounds like quite an impediment. Any idea when v6.0 is likely to be 
> released?

Robert,

I would say late summer or early fall.  However, I would also encourage
you to try out the single-pass-query in the development version before
then. I don't think this is available yet though.

Best regards,
-- 
---------------------------------------+--------------------------------------
I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush    | Geospatial Programmer for Rent

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