[gdal-dev] Delete a sqlite database

[Jason Roberts]

Hi Ludovic and Frank,

As I understand from discussions with Evan Rouault, Destroy() is an obsolete
method in the Python bindings that should not be used. See
http://trac.osgeo.org/gdal/wiki/PythonGotchas#CertainobjectscontainaDestroym
ethodbutyoushouldneveruseit.

If that understanding is not correct, please let me know.

Rather than calling Destroy(), it might be better to set all of the
variables to None (i.e. joinlayer, layer, and datasource) to hopefully cause
Python to destruct these instances. But I see from Ludovic's latest email
that he tried it and it did not work. So it is time for a new idea...

In any case, please let me know if there is a scenario in which Destroy() is
supposed to be called from the Python bindings, contrary to Evan's advice.

Thanks,
Jason

-----Original Message-----
From: gdal-dev-bounces at lists.osgeo.org
[mailto:gdal-dev-bounces at lists.osgeo.org] On Behalf Of Frank Warmerdam
Sent: Monday, November 22, 2010 9:24 AM
To: Ludovic Granjon
Cc: gdal-dev at lists.osgeo.org
Subject: Re: [gdal-dev] Delete a sqlite database

Ludovic Granjon wrote:
> Hi all
> I try in a python script to delete a sqlite database that I use in an 
> OGR ExecuteSQL.
> Let me give you an example :
> If I do :
> 
>  >>> from osgeo import *
>  >>> import os
>  >>> datasource = ogr.Open("decoupe.shp")
>  >>> layer = datasource.GetLayer()
>  >>> joinLayer=datasource.ExecuteSQL("SELECT decoupe.FID as ligne_id, 
> c.lFid as ligne_id2, c.count as count FROM decoupe LEFT JOIN 
> 'project.sqlite'.comptage c ON decoupe.FID=c.lFid")
>  >>> datasource.Destroy()
> 
> It seems that there still a connection to my sqlite database and I can't 
> delete it.
> 
> When I try on MS Windows (There's no error on linux) :
>  >>> os.remove('project.sqlite')
> 
> I have :
> Traceback (most recent call last):
> File "<pyshell#5>", line 1, in <module>
> os.remove('project.sqlite')
> WindowsError: [Error 13] Le processus ne peut pas accéder au fichier car 
> ce fichier est utilisé par un autre processus: 'project.sqlite'
> 
> 
> Do you know a way to do that ?

Ludovic,

I think newish versions of the Python bindings attempt to keep the
datasource
alive as long as their are references to layers from it.  I would suggest
setting layer and joinLayer variables to None before calling destroy on the
datasource or even just setting the datasource to None.  I'm not positive
that
this is the issue - perhaps you could let us know if it works.

Best regards,
-- 
---------------------------------------+------------------------------------
--
I set the clouds in motion - turn up   | Frank Warmerdam,
warmerdam at pobox.com
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush    | Geospatial Programmer for Rent

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