Implement ST_Point

[kylebarron]

It seems that the extension metadata isn't getting passed through here correctly.

I've added a test case that shows that there are two places internally where the extension metadata is correct (assertions pass; the result of return_field_from_args and the value of args.return_field in invoke_with_args). But if I collect the data into record batches with sql_df.collect(), the result schema is missing the Arrow extension metadata (assertion fails).

@timsaucer do you know if I'm doing something wrong here? Or maybe this is an edge case because I'm passing a literal into the SQL command ("SELECT ST_Point(-71.104, 42.315);")?

Elsewhere the extension metadata seemed to correctly exist on the schema of the resulting record batches. In particular, in the test testing ST_AsBinary the relevant line succeeds

geoarrow-rs/rust/geodatafusion/src/udf/native/io/wkb.rs

Lines 210 to 211 in 26f2b6a

	let output_field = output_schema.field(0);
	let output_wkb_type = output_field.try_extension_type::<WkbType>().unwrap();

[kylebarron]

I pushed another test that shows that this works from an existing table; it just fails from a scalar apparently. @timsaucer maybe I should create an issue upstream for this?

[paleolimbot]

Maybe apache/datafusion#15797 is a good place to track? I haven't gotten a chance to try this on scalars yet but there's definitely no ScalarValue::xx that is capable of transporting metadata at the moment.

[timsaucer]

I think I've tracked down the problem. I'll probably get to this today or tomorrow.

[kylebarron]

Thank you! No rush on this from my side; I'm just prototyping.

[timsaucer]

This has bearing on my work as well, so getting these bugs squashed fast is important.

[kylebarron]

I'm going to ignore the failing test on the scalar so I can merge this.