[gdal-dev] Rename and Reorder Layers?

[bas smit]

Dear Even Rouault

I  was also  wondering to know if it is possible to rename the raster bands
?

Bas


On Thu, Jul 17, 2014 at 8:29 PM, Even Rouault <even.rouault at mines-paris.org>
wrote:

> Nik,
>
> > I have two simple questions (not sure if the answers are as simple)...
> >
> > 1.  Is it possible to rename an OGR layer in place within a writeable
> data
> > store without first creating a copy of the entire layer?
>
> There's no provision in the OGR API to do that currently. Although it
> could be
> nice to have. That would require of course updating the drivers that would
> support that capability, and which are coded currently under the
> assumption that
> the layer name is immutable.
> For which driver(s) would you be interested to have that capability ?
>
> >
> > The only way I've found to do this is to use OGR_DS_CopyLayer() (or
> similar)
> > and then delete the old layer which is fairly expensive as it has to
> copy all
> > of the features as well.
>
> For drivers that are related to SQL databases, issuing an "ALTER TABLE foo
> RENAME TO bar" with ExecuteSQL(), and re-opening the datasource afterwards
> (OGR
> will not notice the change) should do it.
>
> >
> > 2.  Is it possible to change the order of layers within a writeable OGR
> data
> > store?  (Ie, change the ordering/indexing of layers as they would be
> > retrieved with OGR_DS_GetLayer() ).
>
> That would be much more involved, not to say impossible. For example, for
> SQL
> based drivers, the driver list is issued from a request in system tables or
> other tables and there's nothing to control the order of retrieval.
> For filebased drivers, such as a directory of shapefiles, it depends on the
> order of the operating system in which it return the filenames. Nothing
> you can
> have control on.
> To make it possible reliably would probably involve adding a special OGR
> metadata table with (order_number, layer_name) columns.
> A potential workaround is to use a OGR VRT file as a thin wrapper above
> your
> "real" datasource. The layers will be ordered in the order they are listed
> in
> the VRT.
>
> Best regards,
>
> Even
>
> --
> Geospatial professional services
> http://even.rouault.free.fr/services.html
>
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