Use separated Coords

[JosiahParry]

Per recommendation separated x &y coordinates should be used when creating a geoarrow array as it will improve conversion to R types.

Comment: https://github.com/geoarrow/geoarrow-c/issues/78

Example affected lines: https://github.com/JosiahParry/serde_esri/blob/1f7f70e086463079bc2d99b925580e052b7382be/src/arrow_compat.rs#L209

@kylebarron

[paleolimbot]

FWIW, interleaved coords will still work and the optimizations that I'm talking about aren't implemented quite yet. The optimizations I'm talking about are:

• Conversion to wk::xy(), which, under the hood, is the same as geoarrow.point with separated coordinates. nanoarrow doesn't currently do ALTREP for double, so this will incur a copy right now, although the conversion today is still much faster than converting interleaved coordinates (because for anything I haven't optimized I go through the "generic" conversion which has lots of overhead).
• Conversion to sfc. This is probably the same for both interleaved and separated right now, but because matrices store columns together in R, I will probably optimize the separated coordinate -> sfc conversion first. Because sfc is pretty slow anyway after constructing it this one might not matter.

If ESRI JSON is similar to GeoJSON I imagine constructing the interleaved version is easier to do from your end. All this to say that I think you can safely defer this one for quite a while if you'd like 🙂

[JosiahParry]

Thanks for the heads up! Esri JSON is quite quite close to geojson coords are structured like [[x, y, z, m], [x, y, z, m]]. Fortunately the conversion to geoarrow falls (almost) entirely on geoarrow-rs.

The way it works is that I have my struct EsriPolygon, for example, where I have to implement the trait PolygonTrait which defines how to get x & y coords out of the struct. Then once that trait is defined I get for "free" the ability to create a PolygonArray using geoarrow-rs. However, at present that assumes an interleaved coordinate buffer. But it seems like moving forward I'll have the option to choose the coordinate representation type https://github.com/geoarrow/geoarrow-rs/pull/279

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Aside: I suspect any use of geoarrow or more low-level geometry representations will lead to a massive speed up regardless of a copy or not :)

[paleolimbot]

Aside: I suspect any use of geoarrow or more low-level geometry representations will lead to a massive speed up regardless of a copy or not :)

It's true. I've even found so far that Arrow WKB is a huge speed boost (compared to anything involving lists of R objects).