[gdal-dev] [python] CopyDataSource question

[Even Rouault]

Frank,

> Hi,
>
> I have (again) a question concerning the Driver.CopyDataSource() method
> using OGR Python bindings
>
> I've written some code that copies a datasource to another format, using
> a target driver and its CopyDataSource() method. This works fine for
> GDAL version 1.7.3, but fails under 1.8.0. Failing means that the
> CopyDataSource call is made but never finishes. It just sits there and
> does nothing. This is however related to *my code*, and *not* an OGR
> error.

Reading your further explanations, it is difficult to know if it's a problem in
your code, or in OGR.

> Doing the task with OGR classes directly works.

What do you mean by "with OGR classes" ? Do you mean when not using
CopyDataSource() ?

> But I wonder why
> my script runs fine on one system but not on the other.

One system with 1.7.3 and the other with 1.8.0 ?

>
> I have some sample test data with which I test my code. The sample is a
> point shapefile and I copy it to GeoJSON, GML and KML formats. The
> GeoJSON still works, but the GML test fails, and KML also.
>
> So my question (at last ;-)): What could make the CopyDataSource fail
> with GML and KML, but succeed with GeoJSON? And make it completely
> succeed under GDAL 1.7.3?

That stalling in CopyDataSource() doesn't sound good. I've no ready-made
explanation for this. Would you be able to create a minimalistic standalone
python script of just a few lines of code (not your entire python code), with
associated test data, that can be used to replicate the issue ?

Which OS do you use ? Did you compile GDAL by yourself or do you use a binary
distribution ?

Provided you have a version of the GDAL librairy with debugging symbols, you
could try attaching a debugger to the process and observe what happens step by
step in CopyDataSource().

>
> Looking at ogr2ogr.py, CopyDataSource is never used there.

Yes, ogr2ogr offer more options and can do more advanced transformations than
CopyDataSource() can do, so it needs control at the layer and feature level.

> Am I abusing
> CopyDataSource? Is it the right tool to copy a datasource to a new format?

CopyDataSource() is very basic, but it should work for what it is supposed to
do, and not block forever.

Best ragards,

Even