Am 21.11.2011 19:57, schrieb Even Rouault:
Le lundi 21 novembre 2011 11:20:33, Ari Jolma a écrit :
Hi,
I'm making a new GML layer from an existing layer. For some reason the
CopyLayer method leaves adjusted fields out but CreateField,
CreateFeature sequence does not. I guess they should be identical?
i.e.
my $datasource = Geo::OGR::Open('Pg:...');
my $l = $datasource->ExecuteSQL('...');
my $gml = Geo::OGR::Driver('GML')->Create('/vsistdout/');
$gml->CopyLayer($l, 'a');
leaves fields like "a b" out, while
I guess it is because the GML driver transforms "a b" into "a_b" to make it a
valid XML name. But the implementation of CopyLayer() uses SetFrom(), which
cannot guess that "a b" values from source feature should be mapped to "a_b"
of target feature.
my $datasource = Geo::OGR::Open('Pg:...');
my $l = $datasource->ExecuteSQL('...');
my $gml = Geo::OGR::Driver('GML')->Create('/vsistdout/');
my $l2 = $gml->CreateLayer('test');
my $d = $l->GetLayerDefn;
for (0..$d->GetFieldCount-1) {
my $f = $d->GetFieldDefn($_);
$l2->CreateField($f);
}
$l->ResetReading;
while (my $f = $l->GetNextFeature) {
$l2->CreateFeature($f);
}
works ok (and prints out warnings about the field name adjustments)
Works ok perhaps, but it is potentially risky. You should not use $l2-
CreateFeature($f) with $f being a feature that has the feature definition of
$l and not $l2. That could crash in some situations... You're lucky here that
it works for you because you have the same number of fields and same type.
I tried to look into what the CopyLayer method generic driver does
differently but could not tell.
CopyLayer() should likely implement the more advanced tricks that ogr2ogr.cpp
uses to do the proprer mapping of field names, even when renames occur.
Any ideas?
Ari
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Hi,
another thing I noticed while using CopyDataSource, which might be
related to CopyLayer, that's why I am posting this here: the driver is
lost, don't know if this is intentional ... see the short code example below
Python 2.6.6 (r266:84292, Dec 26 2010, 22:31:48)
[GCC 4.4.5] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> from osgeo import ogr
>>> in_ds = ogr.Open('points.shp')
>>> in_ds.GetDriver()
<osgeo.ogr.Driver; proxy of <Swig Object of type 'OGRDriverShadow *' at
0x7f919c6f7fc0> >
>>> in_drv = in_ds.GetDriver()
>>> out_ds = in_drv.CopyDataSource(in_ds, 'cp.shp')
>>> out_ds.GetDriver()
>>> out_drv = out_ds.GetDriver()
>>> out_drv is None
True
>>>
Greetings
Frank
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technologies d'information géographique
rue des Romains 36
L-5433 NIEDERDONVEN
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