S2 Cell Id functions for PostgreSQL and PostGIS

This extension makes it easy to convert GIS data to S2 data types - s2 cell ids and s2 cell id tokens in particular.

To use, you must install plpython3u (the PostgreSQL language) and s2sphere (the python3 exstension) on your postgresql server.

sudo apt-get install postgresql-plpython3-9.6
sudo pip3 install s2sphere

To install the extension, clone the respository on your server, then:

sudo make install && make installcheck

Finally, to actually use the extension:

CREATE LANGUAGE plpython3u;
CREATE EXTENSION s2;

SELECT s2_cellid_from_latlng(10.1234, -72.1234);

S2 cell ids are 8-bytes, so fit nicely in PostgreSQL's bigint. Tokens are a hex-encoding with the trailing 0's removed, so fit nicely as text.

Either representation will work well for sorted indices. I generally prefer the bigint ids but try to provide functions for both when appropriate.

If you're looking at the implementation, there is a dance around converting the unsigned representation used by python3 and s2sphere and the signed PostgreSQL implementation.

Functions are added completely opportunistically, so feel free to request something or contribute! If we've missed some best practices or you want to convert it to use the c library instead of python, let me know!