Thanks for the pointer. I opened an issue.
-erik
> On Jul 21, 2025, at 10:17, Even Rouault <even.roua...@spatialys.com> wrote:
>
> Erik,
>
> I don't think it is really worth sozip'ing a zipped Zarr, given that zarr is
> made of many relatively small files, and sozip shines with big compressed
> files. Generally, even when creating a zipped (sozip or not) Zarr file, you
> need to make sure that your writing pattern matches chunks boundaries, to
> avoid chunk files to be rewritten several times and making the zip bigger
> than needed. Please file an issue about the error not being transmitted up to
> the caller
>
> Even
>
> Le 19/07/2025 à 17:44, Erik Schnetter via gdal-dev a écrit :
>> I am using GDAL to create a multidimensional zarr file that is sozip
>> compressed. I see this error when creating the file:
>>
>> ERROR 1: dish_positions.00000000.zarr/zarr.json already exists in ZIP file
>> ERROR 8: Open file
>> /vsizip/data/fengine_init_pathfinder/cx66_dish_positions.00000000.zarr.zip/dish_positions.00000000.zarr/zarr.json
>> to write failed
>>
>> Everything is working fine when I do not use sozip compression. I enable
>> sozip compression by adding a "/vsizip" prefix to the file name. Although
>> there is an error reported on screen, I do not see an error code reported by
>> the function creating or closing the multidimensional dataset. The resulting
>> file ("*.zarr.zip") is created fine and looks almost correct, but all
>> attributes seem to be missing.
>>
>> I wonder – is it actually possible to create a zarr file that is sozip
>> compressed, given that zarr probably writes to each of its file multiple
>> times? If not, what is the preferred way to create a sozip-compressed zarr
>> file efficiently?
>>
>> Some details:
>>
>> I create the dataset (i.e. the file) via
>>
>> const auto driver_manager = GetGDALDriverManager();
>> const auto driver = driver_manager->GetDriverByName("Zarr");
>> const auto dataset =
>> std::unique_ptr<GDALDataset>(driver->CreateMultiDimensional(
>> full_path.c_str(), root_group_options_c.data(),
>> options_c.data()));
>>
>> where "full_path" is
>> "/vsizip/data/fengine_init_pathfinder/cx66_dish_positions.00000000.zarr.zip/dish_positions.00000000.zarr".
>>
>> I then create multiple attributes ("CreateAttribute") and then
>>
>> const auto mdarray = group->CreateMDArray(meta->get_name(),
>> dimensions, datatype,
>> array_options_c.data());
>> const bool success = mdarray->Write(
>> arrayStart.data(), count.data(), nullptr,
>> bufferStride.data(), datatype,
>> frame + datatypesize * meta->offset, frame,
>> buffer->frame_size);
>>
>> and finish with
>>
>> const CPLErr err = dataset->Close();
>> assert(!err);
>>
>> The full code is available at
>> <https://github.com/kotekan/kotekan/blob/eschnett/updates-2/lib/stages/gdalFileWrite.cpp>.
>>
>> -erik
>>
>> _______________________________________________
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>> gdal-dev@lists.osgeo.org
>> https://lists.osgeo.org/mailman/listinfo/gdal-dev
>
> --
> http://www.spatialys.com
> My software is free, but my time generally not.
>
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