BlakeOrth commented on code in PR #8943: URL: https://github.com/apache/arrow-rs/pull/8943#discussion_r2586898642
########## parquet-geospatial/src/types.rs: ########## @@ -0,0 +1,393 @@ +// Licensed to the Apache Software Foundation (ASF) under one +// or more contributor license agreements. See the NOTICE file +// distributed with this work for additional information +// regarding copyright ownership. The ASF licenses this file +// to you under the Apache License, Version 2.0 (the +// "License"); you may not use this file except in compliance +// with the License. You may obtain a copy of the License at +// +// http://www.apache.org/licenses/LICENSE-2.0 +// +// Unless required by applicable law or agreed to in writing, +// software distributed under the License is distributed on an +// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY +// KIND, either express or implied. See the License for the +// specific language governing permissions and limitations +// under the License. + +use arrow::error::Result; +use arrow_schema::{ArrowError, DataType, extension::ExtensionType}; +use serde::{Deserialize, Serialize}; + +/// Hints at the likely Parquet geospatial logical type represented by a [`Metadata`]. +/// +/// Based on the `algorithm` field: +/// - [`Hint::Geometry`]: WKB format with linear/planar edge interpolation +/// - [`Hint::Geography`]: WKB format with explicit non-linear/non-planar edge interpolation +/// +/// See the [Parquet Geospatial specification](https://github.com/apache/parquet-format/blob/master/Geospatial.md) +/// for more details. +#[derive(Copy, Clone, Debug, Serialize, Deserialize)] +pub enum Hint { + /// Geospatial features in WKB format with linear/planar edge interpolation + Geometry, + /// Geospatial features in WKB format with explicit non-linear/non-planar edge interpolation + Geography, +} + +/// The metadata associated with a [`WkbType`]. +#[derive(Clone, Debug, Default, Serialize, Deserialize)] +pub struct Metadata { + /// The Coordinate Reference System (CRS) of the [`WkbType`], if present. + /// + /// This may be a raw string value (e.g., "EPSG:3857") or a JSON object (e.g., PROJJSON). + /// Note: Common lon/lat CRS representations (EPSG:4326, OGC:CRS84) are canonicalized + /// to `None` during serialization to match Parquet conventions. + #[serde(skip_serializing_if = "Option::is_none")] + pub crs: Option<serde_json::Value>, + /// The edge interpolation algorithm of the [`WkbType`], if present. + #[serde(skip_serializing_if = "Option::is_none")] + pub algorithm: Option<String>, +} + +impl Metadata { + /// Constructs a new [`Metadata`] with the given CRS and algorithm. + /// + /// If a CRS is provided, and can be parsed as JSON, it will be stored as a JSON object instead + /// of its string representation. + pub fn new(crs: Option<String>, algorithm: Option<String>) -> Self { + let crs = crs.map(|c| match serde_json::from_str(&c) { + Ok(crs) => crs, + Err(_) => serde_json::Value::String(c), + }); + + Self { crs, algorithm } + } + + /// Returns a [`Hint`] to the likely underlying Logical Type that this [`Metadata`] represents. + pub fn type_hint(&self) -> Hint { + match &self.algorithm { + Some(s) if s.to_lowercase() == "planar" => Hint::Geometry, + Some(_) => Hint::Geography, + None => Hint::Geometry, + } + } +} + +/// Well-Known Binary (WKB) [`ExtensionType`] for geospatial data. +/// +/// Represents the canonical Arrow Extension Type for storing GeoArrow data. +#[derive(Debug, Default)] +pub struct WkbType(Metadata); + +impl WkbType { + /// Constructs a new [`WkbType`] with the given [`Metadata`]. + /// + /// If `None` is provided, default (empty) metadata is used. + pub fn new(metadata: Option<Metadata>) -> Self { + Self(metadata.unwrap_or_default()) + } +} + +impl ExtensionType for WkbType { + const NAME: &'static str = "geoarrow.wkb"; Review Comment: @paleolimbot or @kylebarron are both probably a more authoritative resource on this than I am, but `geoarrow.wkb` is what the C++ parquet/arrow library uses as well: https://github.com/apache/arrow/blob/e90bacded2ae5a34be11c764e00751c18ab3b355/docs/source/cpp/parquet.rst#logical-types I've probably already rocked the boat enough with @paleolimbot in my POC for this PR (https://github.com/apache/arrow-rs/pull/8801), but having one extension type name map to two parquet LogicalTypes does end up causing some headaches, and there is one case that can't really be represented (however, nobody seems very concerned about this case). If the extension names were `geometry.wkb` and `geography.wkb` that could be a bit more clear in my opinion, but using `geoarrow.wkb` seems to be the current community standard, so it's probably best to just stick with it. -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected]
