[gdal-dev] Is using geometry in SQL inside VRT supported?

[Rahkonen Jukka]

Hi Frank,

Great, and I guess that this syntax example about how to select the dialect will be added to the driver manual page http://www.gdal.org/ogr/drv_vrt.html  in your documentation sprint of FOSS4G NA.

-Jukka-

________________________________
Frank Warmerdam wrote:


Jukka,

It turns out you can already assign a dialect.  I think it is roughly like:

  <SrcSQL dialect="sqlite">SELECT ...</SrcSQL>

It seems to be touched on it the docs for the OGR VRT driver as well.

Best regards,
Frank



On Fri, May 24, 2013 at 9:46 AM, Frank Warmerdam <warmerdam at pobox.com<mailto:warmerdam at pobox.com>> wrote:
Jukka,

Agreed!  The SrcSQL directive in the VRT should accept a dialect option.  I'll try to do that this afternoon as we are "sprinting" here at FOSS4G NA and this would be a nice sized feature to add.

Best regards,
Frank



On Fri, May 24, 2013 at 8:39 AM, Jukka Rahkonen <jukka.rahkonen at mmmtike.fi<mailto:jukka.rahkonen at mmmtike.fi>> wrote:
Hi,

This works with ogrinfo
ogrinfo -ro cities.shp  -dialect SQLITE -sql "select GEOMETRY from cities"

I tried to make a VRT file which would do the same

<OGRVRTDataSource>
<OGRVRTLayer name="cities">
<SrcDataSource>cities.shp</SrcDataSource>
<LayerSRS>WGS84</LayerSRS>
<SrcSQL>SELECT GEOMETRY from cities</SrcSQL>
</OGRVRTLayer>
</OGRVRTDataSource>

Now ogrinfo does not find geometries

ogrinfo cities.vrt
INFO: Open of `cities.vrt'
      using driver `VRT' successful.
1: citiesERROR 1: SQL Expression Parsing Error: syntax error
ERROR 1: SQL statement failed, or returned no layer result:
"SELECT GEOMETRY from cities"

This exact use case is not at all interesting but there would be quite nice
possibilities if Spatialite SQL queries could be fired from the VRT and all
this would be supported for on-the-fly conversions
http://www.gaia-gis.it/gaia-sins/spatialite-sql-4.0.0.html



-Jukka Rahkonen-

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--
---------------------------------------+--------------------------------------
I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com<mailto:warmerdam at pobox.com>
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush    | Geospatial Software Developer



--
---------------------------------------+--------------------------------------
I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com<mailto:warmerdam at pobox.com>
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush    | Geospatial Software Developer