TopoJSON

[davenquinn]

Hi! I have been making great use of the GeoJSON generation functionality of PostgREST. I am wondering if there has been any discussion of enabling similar functionality for TopoJSON?

It seems like the API could be essentially the same, e.g., Accept: application/topo+json, since PostGIS already has built-in TopoJSON generation capabilities? There may be performance implications as dumping TopoJSON is more expensive.

[steve-chavez]

Hey @davenquinn,

TIL about TopoJSON, for GeoJSON we create an aggregate/collection of objects using this query:

postgrest/src/PostgREST/Query/SqlFragment.hs

Lines 221 to 222 in b3b4e5f

	asGeoJsonF :: SQL.Snippet
	asGeoJsonF = "json_build_object('type', 'FeatureCollection', 'features', coalesce(json_agg(ST_AsGeoJSON(_postgrest_t)::json), '[]'))"

Do you know how we could do the same for TopoJSON?