[gdal-dev] Gdal 2.0 vs Gdal 1.x : Testing driver capabilities

[Even Rouault]

Hi Julien,
> 
> I am currently trying to make our software (Orfeo ToolBox) both
> compatible with Gdal 1.x (> 1.10) and gdal 2.x. I am almost done but I
> am having a hard time figuring out how to test capabilities on a (former
> OGR) driver.
> 
> Indeed, I can see in ogrsf_frmts.h that OGRSFDriver::TestCapability() is
> deprecated :
> 
> virtual int            TestCapability( const char *pszCap )
> OGR_DEPRECATED("Use GDALDriver class instead") = 0;
> 
> However, I can not find such a service in GDALDriver class ... The only
> TestCapability I found is the one of GDALDataset.
> 
> I am specifically trying to test the ODrCDeleteDataSource capability on
> the driver, and I can not use the GDALDataset::TestCapability() for that
> (or at least it is not listed in supported capabilities in doxygen of
> this method [1]).
> 
> What am I missing here ?

Nothing. There's no equivalent for ODrCDeleteDataSource indeed. In GDAL 
drivers (and thus vector drivers that have been converted to GDAL drivers), 
the Delete() capability is implemented in a generic way by querying the list 
of files that make the dataset and delete them. Drivers may provide a dedicated 
implementation instead of that generic one.
Without a dataset, there's no way to know in advance if calling Delete() is 
going to do something or not. That's perhaps missing indeed.

A potential workaround is to query drivers for GDAL_DMD_CONNECTION_PREFIX 
metadata item that is set for (hopefully most) drivers that are not file based, 
and for which Delete() is generally going to raise an error at runtime.

>>> from osgeo import gdal
>>> gdal.GetDriverByName('MYSQL').Delete('MYSQL:autotest')
ERROR 6: Unable to determine files associated with MYSQL:autotest,
delete fails.
3
>>> gdal.GetDriverByName('MYSQL').GetMetadataItem(gdal.DMD_CONNECTION_PREFIX)
'MYSQL:'
>>> 


Even

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