Awesome
Introduction
This repository contains the specification for the SOZip (Seek-Optimized Zip) profile to the ZIP file format.
What is SOZip ?
A Seek-Optimized ZIP file (SOZip) is a ZIP file that contains one or several Deflate-compressed files that are organized and annotated such that a SOZip-aware reader can perform very fast random access (seek) within a compressed file.
SOZip makes it possible to access large compressed files directly from a .zip file without prior decompression. It is not a new file format, but a profile of the existing ZIP format, done in a fully backward compatible way. ZIP readers that are non-SOZip aware can read a SOZip-enabled file normally and ignore the extended features that support efficient seek capability.
Software implementations
: C/C++ open source geospatial library. Try out its sozip branch, pending future inclusion in its master branch.
- Python sozipfile module: drop-in replacement
for standard
zipfile
module, creating and reading SOZip-enabled files.
See Annex A: Software implementations for more details.
Examples of SOZip files
Examples of SOZip-enabled files can be found in the sozip-examples repository.
Other ZIP related specification
This GitHub organization also hosts the KeyValuePairs extra-field specification, to be able to encode arbitrary key-value pairs of metadata associated with a file within a ZIP. For example to store the Content-Type of a file.
Benchmarking
Done with GDAL sozip branch, on a laptop running a Intel(R) Core(TM) i7-10750H CPU @ 2.60GHz (6 cores / 12 virtual CPUs).
- ZIP generation:
Timing | Action |
---|---|
6.1 s | Multithreaded (12 vCPUs) generation of 489 MB SOZip-enabled file from a 1.6 GB uncompresssed GeoPackage file with<br>sozip nz-building-outlines.gpkg.zip nz-building-outlines.gpkg |
36 s | Single threaded compression of same file to 480 MB with regular zip utility with<br>zip nz-building-outlines-regular.gpkg.zip nz-building-outlines.gpkg |
- Bulk reading: Multithreaded extraction (4 vCPUs) of 3.2 million features with Arrow Array interface
Timing | Action |
---|---|
1.2 s | from SOZip-compressed GeoPackage file with<br>bench_ogr_batch nz-building-outlines.gpkg.zip |
0.7 s | from uncompressed GeoPackage file with<br>bench_ogr_batch nz-building-outlines.gpkg |
- Subsetting: Extraction of 66,377 features with a spatial filter
Timing | Action |
---|---|
1.2 s | from SOZip-compressed GeoPackage file with<br>ogr2ogr out.gpkg nz-building-outlines.gpkg.zip -spat 1740000 5910000 1750000 5920000 |
1.1 s | from uncompressed GeoPackage file with<br>ogr2ogr out.gpkg nz-building-outlines.gpkg -spat 1740000 5910000 1750000 5920000 |
- Extraction of one feature from its identifier:
Timing | Action |
---|---|
45 ms | from SOZip-compressed GeoPackage file with<br>ogr2ogr out.gpkg nz-building-outlines.gpkg.zip -fid 1000000 |
44 ms | from uncompressed GeoPackage file with<br>ogr2ogr out.gpkg nz-building-outlines.gpkg -fid 1000000 |
How to contribute ?
We welcome contributions to this specification as issues, pull requests or discussions.
If you use SOZip or plan to use it for your data delivery, or consider doing a SOZip implementation, etc., let us know!
Datasets available as SOZip
- TUDelft3D delivers the 3DBAG data, an open 3D building dataset, for the whole of the Netherlands, 108 GB uncompressed, as a 18.8 GB large GeoPackage: https://3dbag.nl/en/download
- Raw Data API, from Humanitarian OpenStreetMap Team (HOTOSM), now uses SOZip when you download openstreetmap data .zip files through it.
Social media
Credits
The SOZip specification and its GDAL implementation have been developed by Spatialys, with support from Safe Software
<!--- # Adopters (Put here a list of organizations, in particular data producers, that have adopted SOZip) -->