#23804: Add a RasterField to GeoDjango
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Reporter: yellowcap | Owner: yellowcap
Type: New feature | Status: assigned
Component: GIS | Version: master
Severity: Normal | Resolution:
Keywords: raster gdal | Triage Stage: Accepted
Has patch: 1 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 1
Easy pickings: 0 | UI/UX: 0
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Comment (by yellowcap):
I updated the pull request for the first RasterField implementation. The
raster field should now be fairly complete, but it became quite large due
to that. Its hard to split things at this point though, as the different
elements are quite interrelated. I hope its still an acceptable size.
Here is a description of the current state:
- The field is implemented for PostGIS backends only.
- Similar to `GeometryFields`, the field srid can be specified and the
raster will automatically be transformed to the field srid upon saving.
- A spatial index for the raster is built by default, and can be disabled
with `spatial_index=False`.
- The `null` and `blank` flags can be specified.
- Lazy instantiation works for the raster field as well.
- Tests are in place for the RasterField and corresponding migration
commands and operations
For this, I made some changes on the existing codebase:
- Generalized the `GeometryProxy` and renamed to `SpatialProxy`. This is
used for lazy-instantiation of objects related to spatial fields.
- Override the `get_indexes` introspection function for postgis, as the
spatial indices are based on expressions and are not straight indices
(using `ST_ConvexHull`). So the sql code retrieving the list of indices
has to be adopted to that.
- Update the `get_placeholder` function in the `PostGISOperator` to
implicitly reproject rasters that are passed to a field with a different
srid than the field srid.
- Change in `PostGISSchemaEditor` to create spatial indices on raster
(wrapping the index creation sql with the `ST_ConvexHull` function).
- Split parts of the `GeometryField` into a generalized `BaseSpatialField`
class. The `GeometryField` and the `RasterField` subclass the
`BaseSpatialField`.
- Updated the `gis_migrations` test module to also include the
`RasterField` into the tests.
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Ticket URL: <https://code.djangoproject.com/ticket/23804#comment:29>
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