[gdal-dev] Decoding feature blobs and tracking FIDs in MVT datasets

[Even Rouault]

Hi Linda,

Happy New Year

> I’ve put together a short document with the planned implementations 
> [0]. Could you please take a look (or anyone else interested in this 
> topic) and let me know if this seems okay to implement? Part of the 
> work I have already done, but I’d like to make sure it follows GDAL 
> conventions all the way through.

I've read your detailed document. Your plan looks solid. My main remark 
is that when a driver accepts to open a dataset in GDAL_OF_UPDATE mode, 
it is expected that read operations are still available. Failing to do 
that could cause issues for users/software that always open in update 
mode if possible, even if they end up not doing any change. By using 
OGRMVTWriterDataset which is write-only, you wouldn't be able to meet 
that expectation. It could be complicated to extend OGRMVTWriterDataset 
to have read capabilities (especially since the writing side generates 
several zoom levels at once, whereas the reading side has one dataset 
per zoom level), so I would suggest that the update mode you describe is 
triggered by both GDAL_OF_UPDATE and a specific open option like 
EDIT_ONLY=YES / UPDATE_ONLY=YES. Or maybe just the later.

If you plan to implement updates of existing features, implementing 
ISetFeature() only would be sufficient. IUpdateFeature() is reserved for 
drivers that can offer such capability naturally, typically drivers for 
a SQL database.

Even

-- 
http://www.spatialys.com
My software is free, but my time generally not.
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