Support geography columns

[pramsey]

Geography columns are not automatically discovered in the catalog query, and may require special handling in the tile generation queries as well.

[stephenhillier]

I could submit a PR to solve this in a basic way by letting the table query discover geography columns and then casting to geometry before generating the tiles, but is that too simple? Would a linestring stored as geography have to be visualized as a great arc in order to be consistent with calculations using that same linestring?

[pramsey]

Hm... the tiles themselves are planar (3857) ... I think the main downside of casting agressively is that if the tables are using spatial indexes on geography you're getting no benefit out of them.

[joleeee]

Is this planned?

[pramsey]

It's not on a schedule or anything. It's a reasonable feature request, so I'm not closing it out. Patches accepted! It'll be kind of a big patch, I think unfortunately, since the SQL necessary to efficiently generate tiles from geography will be a bit different from that required for the pure geometry case.