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

Wed Apr 10 17:48:22 PDT 2013

Don't think so... This for drawing. Still could be an issue, but I hope not.

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From: mapserver-dev-bounces at lists.osgeo.org [mapserver-dev-bounces at lists.osgeo.org] on behalf of Brent Fraser [bfraser at geoanalytic.com]
Sent: Wednesday, April 10, 2013 5:08 PM
To: deuce2367
Cc: mapserver-dev at lists.osgeo.org
Subject: Re: [mapserver-dev] OGR/MySQL Layer executes SQL query twice

Any,

 Back in late 2009 (search the email list in Dec 2009 and Mar 2010) there was an effort to implement RFC 52: One-pass query processing (http://mapserver.org/development/rfc/ms-rfc-52.html), but I'm not sure if it was implemented. (Status=draft?).

  Dunno if it relates to your problem...

Best Regards,
Brent Fraser

On 4/10/2013 2:23 PM, deuce2367 wrote:
Steve,

That's a good suggestion.  I'm running a very simple test where I use shp2img with a straightforward map file but if I used ogr2ogr that would take Mapserver out of the equation altogether.  I'll try and set up such a test and see what happens.

Cheers,

-Andy

On Wed, Apr 10, 2013 at 2:06 PM, Lime, Steve D (MNIT) [via OSGeo.org] <[hidden email]</user/SendEmail.jtp?type=node&node=5045913&i=0>> wrote:
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.

Steve

-----Original Message-----
From: [hidden email]<http://user/SendEmail.jtp?type=node&node=5045879&i=0> [mailto:[hidden email]<http://user/SendEmail.jtp?type=node&node=5045879&i=1>] On Behalf Of deuce2367
Sent: Tuesday, April 09, 2013 9:20 AM
To: [hidden email]<http://user/SendEmail.jtp?type=node&node=5045879&i=2>
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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