[mapserver-dev] OGR/MySQL Layer executes SQL query twice

Lime, Steve D (MNIT) Steve.Lime at state.mn.us
Wed Apr 10 11:06:02 PDT 2013

Is there a way to test your theory independent of MapServer using OGR only? I don't know the MapServer OGR driver well but I can't imagine this is normal.


-----Original Message-----
From: mapserver-dev-bounces at lists.osgeo.org [mailto:mapserver-dev-bounces at lists.osgeo.org] On Behalf Of deuce2367
Sent: Tuesday, April 09, 2013 9:20 AM
To: mapserver-dev at lists.osgeo.org
Subject: [mapserver-dev] OGR/MySQL Layer executes SQL query twice

I'm using Mapserver 6.0.2 and GDAL 1.7.2 and have created a mapfile with an OGR/MySQL layer.  The SQL query that retrieves the spatial data is fairly slow, takes about 8-10 seconds.  I've noticed that whenever I render the layer (via the mapserv binary or via the shp2img utility) that the query executes two times.  I thought this was maybe some sort of introspection/reflection issue where perhaps OGR is trying to characterize the data somehow so I made sure to create and populate the geometry_columns table but that doesn't seem to help, it's still running the SQL query twice. 
Incidentally it's also performing 2 describes and 2 'select from geometry_columns...' as well.

Is this normal and expected? 

I apologize if this is a repeat, I didn't find any references to this observation in my searches.  Appreciate any help,

-Andy Smith

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