[QGIS-Developer] Fwd: [gdal-dev] Announcing SOZip: Seek-Optimized profile for the .zip format

[Even Rouault]

Le 09/01/2023 à 16:54, Richard Duivenvoorde a écrit :
> Hi Even,
>
> Cool!
>
> Out of curiosity: I thought sqlite/geopackage was already relatively 
> 'skinny' packed? Am I wrong?
Well, SQLite does some packing of integer or floating-point values, but 
nothing on strings or blobs (which means no compression o the WKB 
extended geometries of GeoPackage). You can get easily a 3x compression 
ratio when zipping GeoPackage vector files (of course depends a lot on 
what you put in them)
>
> Anybody has experience with zipping "laaaarge zipped GeoPackages"? ;-) 
> Is that useful? I just tested a 885MB mbtiles file (I know not 
> geopackage...but still sqlite isnt't it?), and that ended up in 868MB.

I have successfully tested a ~30 GB uncompressed GeoPackage vector file 
compressed as ~10 GB as SOZip.

MBTiles holds PNG or JPEG tiles which are already compressed, so no 
surprise that the Deflate compression of ZIP doesn't help.

>
> OR... are we talking about sets of geopackages?

The SOZip spec is all about laaarge-files-in-zip. Considerations of 
many-files-in-zip are not covered by it (they are orthogonal)


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