DuckDB datasource

[nicokant]

I think it would be very usuful to have a DuckDB datasource for both (vector) tile service and features service, this would allow a lot of flexibility in terms of supported formats and queries, since DuckDB with the spatial extension is able to read most of the GDAL sources.
For the tile service, there's unfortunately no st_toMVTGeom function in DuckDB now, but it's possible to read the convert the output geometry (usually wkb) to a MVT tile using geozero.

[pka]

In fact, I'm currently experimenting with an integration of DuckDB in an other project. So far I saw two drawbacks:

• Release build time with an embedded DuckDB library goes easily up by more than 10 minutes for each platform. I even hit the Github CI limit because of that
• Extensions are downloaded at runtime. This makes packaging for different platform much more involved, if you want to avoid that

Use cases for me are supporting more formats, as you mention and specifically reading GeoParquet sources like the Overture Maps dataset.

[nicokant]

My main use case for Tile service is also serving GeoParquet, possibly generating at runtime the tile rather than pre-computing it, but this would potentially allow also to serve other file types (like duckdb database files for example).
I'm unfortunately not very familiar with rust, so I can't really say, but wouldn't it be possible to require it installed as an external library?
About the extension, it's true that they are downloaded at runtime, but this happens only once, if you want to skip it the service could check if a duckdb datasource is present and in case run the install. To persist the loaded extension it's also possible to use a duckdb database file created at startup that install and loads the extensions. All the subsequent execution use that database in readonly mode to fetch the data. This of course has some drawbacks, but it seems more reasonable to handle than the other one

[nicokant]

This might also be relevant: duckdb/duckdb-spatial#241

[yharby]

relevant ? https://github.com/l1xnan/duckling