[gdal-dev] Rename and Reorder Layers?

[Even Rouault]

Selon bas smit <baspysmit at gmail.com>:

> Dear Even Rouault
>
> I  was also  wondering to know if it is possible to rename the raster bands
> ?

Bas,

You can attach a description to bands with SetDescription(). But not so many
formats support that natively. HFA Imagine is one of those few. Other PAM based
drivers will save the description in the .aux.xml file associated with the
dataset, so that will work only in the GDAL world.

Even

>
> 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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> >
>