[gdal-dev] Re: Rasterlite / WSGI problem

[Even Rouault]

Selon Radim Blazek <radim.blazek at gmail.com>:

> I'll reply to myself in case anyone have the same problem.
>
> Apache is linked to SQLite. SQLite from deb is not compiled with
> rtree. WSGI is started as Apache fork, so the process has SQLite (from
> /usr/lib/) already loaded and later explicit loading of SQLite lib
> with rtree cannot help.
>
> I solved it setting LD_LIBRARY_PATH to point to SQLite with rtree in
> /etc/apache2/envvars. I had also tried to compile GDAL staticaly
> linked to SpatiaLite but it was not working.

I've never tried static linking with spatialite. Perhaps some configure.in
tweaking required here

>
> BTW, if RasterliteBand::IReadBlock fails, it does not return an error
> and silently sets image to black (rasterlitedataset.cpp:98):
>
>     OGRLayerH hSQLLyr = OGR_DS_ExecuteSQL(poGDS->hDS, osSQL.c_str(),
> NULL, NULL);
>     if (hSQLLyr == NULL)
>     {
>         memset(pImage, 0, nBlockXSize * nBlockYSize * nDataTypeSize);
>         return CE_None;
>     }
>
> Is it OK?

Perhaps CE_Failure would be more appropriate indeed. In the event of an empty
result set, this should return a valid layer, so NULL is definitely when
something is wrong. You can try returning CE_Failure and if it works as you
expect, feel free to commit the change.

>
> Radim
>
> On Sat, Nov 26, 2011 at 11:45 AM, Radim Blazek <radim.blazek at gmail.com>
> wrote:
> > Hi.
> >
> > We cannot get Mapserver python mapscript running as WSGI with
> > Rasterlite data working. Only a black rectangle is drawn instead of
> > the raster. The rectangle is drawn on the right place however.
> > Rendering takes very little time, so it seems that no image processing
> > is done.  Spatialite/OGR works correctly (using geometry column from
> > raster _metadata table). All other raster/vector data work well.
> >
> > The strange thing is, that everything works well, if exactly the same
> > configuration is run as CGI.
> >
> > I thougt that threads could be a problem, so I disabled treads where
> > possible, but no effect.
> >
> > Rasterlite data: JPEG or EPSILON, JPEG or EPSILON overviews, SRID correctly
> set
> > GDAL 1.8.1 --with-threads=no
> > Mapserver 6.0.1  patched to use GDALOpen instead of GDALOpenShared
> > WSGI: processes=1 threads=1
> >
> > Radim
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