james-willis commented on code in PR #749:
URL: https://github.com/apache/sedona-db/pull/749#discussion_r3113083395
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rust/sedona-schema/src/raster.rs:
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@@ -16,34 +16,33 @@
// under the License.
use arrow_schema::{DataType, Field, FieldRef, Fields};
-/// Schema for storing raster data in Apache Arrow format.
-/// Utilizing nested structs and lists to represent raster metadata and bands.
+/// Schema for storing N-dimensional raster data in Apache Arrow format.
+///
+/// Each raster has a CRS, an affine transform, explicit spatial dimension
names
+/// (`x_dim`, `y_dim`), and a list of bands. Each band is an N-D chunk with
named
+/// dimensions, a shape, and optional strides for zero-copy slicing.
+///
+/// Legacy 2D rasters are represented as bands with `dim_names=["y","x"]` and
+/// `shape=[height, width]`.
#[derive(Debug, PartialEq, Clone)]
pub struct RasterSchema;
+
impl RasterSchema {
/// Returns the top-level fields for the raster schema structure.
pub fn fields() -> Fields {
Fields::from(vec![
- Field::new(column::METADATA, Self::metadata_type(), false),
- Field::new(column::CRS, Self::crs_type(), true), // Optional: may
be inferred from data
+ Field::new(column::CRS, Self::crs_type(), true),
+ Field::new(column::TRANSFORM, Self::transform_type(), false),
+ Field::new(column::X_DIM, DataType::Utf8View, false),
+ Field::new(column::Y_DIM, DataType::Utf8View, false),
Field::new(column::BANDS, Self::bands_type(), true),
])
}
- /// Raster metadata schema
- pub fn metadata_type() -> DataType {
- DataType::Struct(Fields::from(vec![
- // Raster dimensions
- Field::new(column::WIDTH, DataType::UInt64, false),
- Field::new(column::HEIGHT, DataType::UInt64, false),
- // Geospatial transformation parameters
- Field::new(column::UPPERLEFT_X, DataType::Float64, false),
- Field::new(column::UPPERLEFT_Y, DataType::Float64, false),
- Field::new(column::SCALE_X, DataType::Float64, false),
- Field::new(column::SCALE_Y, DataType::Float64, false),
- Field::new(column::SKEW_X, DataType::Float64, false),
- Field::new(column::SKEW_Y, DataType::Float64, false),
- ]))
+ /// Affine transform schema — 6-element GDAL GeoTransform:
+ /// `[origin_x, scale_x, skew_x, origin_y, skew_y, scale_y]`
+ pub fn transform_type() -> DataType {
+ DataType::List(FieldRef::new(Field::new("item", DataType::Float64,
false)))
}
Review Comment:
> X_DIM + Y_DIM should probably also be a list to allow for future Z. Lists
are kind of a pain in Rust but interacting with these in Python is fairly easy
to do and this PR is probably the only one that needs to consider that detail.
Sorry I'm not clear what you want me to do. Should I decompose this into 2
instances of some GeoTransformDimension type?
I adopted this norm to match GDAL. I my assumption was that X and Y are
somewhat privileged in the system. I hadn't given much thought to affine
transformations outside of the xy plane.
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