#25342: Altitude of Point object for equality check
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Reporter: Bhargav Kowshik | Owner: nobody
Type: Bug | Status: new
Component: GIS | Version: dev
Severity: Normal | Resolution:
Keywords: geodjango, equality | Triage Stage: Accepted
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
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Comment (by Olivier Tabone):
Prior 3.12.0, GEOS already has [https://github.com/libgeos/geos/pull/810
multiple equality functions]:
- `GEOSEquals` (which uses topological equality, returning true for
different representations of the same structure)
- `GEOSEqualsExact` (which uses pointwise equality, but allows for a
distance tolerance and ignores Z/M values)
currently, django uses
[https://libgeos.org/doxygen/geos__c_8h.html#a23922c100edd72a8d82720213607e7bf
GEOSEqualsExact] in the
[https://github.com/django/django/blob/95e4d6b81312fdd9f8ebf3385be1c1331168b5cf/django/contrib/gis/geos/geometry.py#L144
__eq__() method] which is not a good fit regarding equality semantics when
z is used (thus this ticket).
`GEOSEquals()` does not work in 3D
[https://libgeos.org/doxygen/geos__c_8h.html#a45499a7d87851015d36e57d285da9d8e
as documented] which is not a good fit regarding equality semantics
either.
GEOS 3.12 introduces `GEOSEqualsIdentical` which is a good fit for
python's equality semantic in 2D and 3D.
I would suggest:
- implementing the `GEOSGeometryBase.equals_identical()` method,
available if GEOS >= 3.12.0. That should be an easy call, pure additive.
(new ticket ?)
- raising a warning if `GEOSGeometryBase.__eq__()` is called with one
operand having a third dimension (`geom.hasZ == True`). To fix this
warning, one should either use an explicit comparaison method
(`GEOSGeometryBase.equals()`, `GEOSGeometryBase.equals_exact()`,
`GEOSGeometryBase.equals_identical()`) or use a 2D point.
- when GEOS 3.12 becomes the minimum supported version, use
GEOSEqualsIdentical to perform `GEOSGeometryBase.__eq__()`. This will
give some time for one to adapt their code bases.
What do you think ?
--
Ticket URL: <https://code.djangoproject.com/ticket/25342#comment:6>
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