OOh, ok!!! Thanks!!
De: Laurențiu Nicola
Enviado el: dilluns, 31 de juliol de 2023 15:24
Para: Abel Pau
CC: gdal-dev@lists.osgeo.org,
Asunto: Re: [gdal-dev] A question of eficiency
Hi,
GetFeatureCount() exists for GDAL users, not for driver writers. For example,
in QGIS, you can right-click
Hi,
GetFeatureCount() exists for GDAL users, not for driver writers. For example,
in QGIS, you can right-click on a layer, choose "Show Feature Count" and you'll
see the number of features next to the layer name.
Or, to give another example, a hypothetical application could use it to display
m>
Enviat: divendres, 21 de juliol de 2023 19:32
Per a: Abel Pau<mailto:a@creaf.uab.cat>;
gdal-dev@lists.osgeo.org<mailto:gdal-dev@lists.osgeo.org>
Tema: Re: [gdal-dev] A question of eficiency
Abel,
OK, I now better understand what you meant. Well, no, there's no way
nviat: divendres, 21 de juliol de 2023 19:32
Per a: Abel Pau<mailto:a@creaf.uab.cat>;
gdal-dev@lists.osgeo.org<mailto:gdal-dev@lists.osgeo.org>
Tema: Re: [gdal-dev] A question of eficiency
Abel,
OK, I now better understand what you meant. Well, no, there's no way
with change radically. Thankss!
*De:*gdal-dev *En nombre de *Abel Pau
*Enviado el:* divendres, 7 de juliol de 2023 12:44
*Para:* Even Rouault ;
gdal-dev@lists.osgeo.org
*Asunto:* Re: [gdal-dev] A question of eficiency
Hi again,
I can totally give this number in GetFeatureCount(). No problem from
!
De: gdal-dev En nombre de Abel Pau
Enviado el: divendres, 7 de juliol de 2023 12:44
Para: Even Rouault ; gdal-dev@lists.osgeo.org
Asunto: Re: [gdal-dev] A question of eficiency
Hi again,
I can totally give this number in GetFeatureCount(). No problem from my driver
to other.
Then I understand
With some formats sizeof, fseek and ftell can be most useful
> On Jul 7, 2023, at 5:33 AM, Abel Pau wrote:
>
> Hi,
> I would like to know if when we use the code of GDAL to program a driver (or
> whatever) in vectors (so, ogr) we can assume that we can know the number of
> elements we are
that, but...
Thanks for your kind anwser!
De: Even Rouault
Enviado el: divendres, 7 de juliol de 2023 12:32
Para: Abel Pau ; gdal-dev@lists.osgeo.org
Asunto: Re: [gdal-dev] A question of eficiency
Abel,
At the minimum for the reading side of a vector driver, you need to implement
GetNextFeature
Abel,
At the minimum for the reading side of a vector driver, you need to
implement GetNextFeature().
If there is an efficient way of knowing the number of features without
iterating over the whole file (typically a field in a header giving that
number), you may implement GetFeatureCount().
Hi,
I would like to know if when we use the code of GDAL to program a driver (or
whatever) in vectors (so, ogr) we can assume that we can know the number of
elements we are going to import in any way or it would be possible not knowing
that until NextFeature is empty (or something like that).
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