#33344: Define bounds transform for discrete postgres range fields
-------------------------------------+-------------------------------------
Reporter: Vidir | Owner: (none)
Valberg Gudmundsson |
Type: New | Status: new
feature |
Component: | Version: dev
contrib.postgres |
Severity: Normal | Keywords:
Triage Stage: | Has patch: 0
Unreviewed |
Needs documentation: 0 | Needs tests: 0
Patch needs improvement: 0 | Easy pickings: 0
UI/UX: 0 |
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The fix for https://code.djangoproject.com/ticket/27147 adressed the issue
of non-discrete range types. Left is the issue of how the ranges are
"represented" when brought back from the database.
At $WORK we have a model like so:
{{{
class Foo(models.Model):
...
period = models.DateRangeField()
}}}
The problem arises when we display the periods of multiple `Foo`s. Using
the default bound of `[)` returned by postgres means that adjacent `Foo`s
"visually" share a date in the upper of one and lower of the other. We
could of course handle this ''each time'' we output the value by
decrementing the upper value. But this is a bit error prone and can lead
to confusions.
I propose that we add the following to
`django.contrib.postres.fields.ranges` (heavily inspired by Jakub
Skałeckis comment at
https://code.djangoproject.com/ticket/27147#comment:8):
{{{
class DiscreteRangeField(RangeField):
def __init__(self, *args, bounds_transform=CANONICAL_RANGE_BOUNDS,
**kwargs):
if bounds_transform not in ALLOWED_BOUNDS:
raise ValueError("bounds_transform must be one of '[)', '(]',
'()', or '[]'.")
self.bounds_transform = bounds_transform
super().__init__(*args, **kwargs)
def from_db_value(self, value, expression, connection):
if value is None:
return
if self.bounds_transform[0] == "(" and value.lower:
value._lower = value.lower - self.bounds_transform_unit
if self.bounds_transform[1] == "]" and value.upper:
value._lower = value.upper - self.bounds_transform_unit
value._bounds = self.bounds_transform
return value
}}}
and make `IntegerRangeField`, `BigIntegerRangeField` and `DateRangeField`
inherit from `DiscreteRangeField`.
I have already written some tests, and if there are no big gotchas to this
approach I would love to submit a PR in the next couple of days.
--
Ticket URL: <https://code.djangoproject.com/ticket/33344>
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