#36031: DecimalRangeField __contains query for a value causes DataError
-------------------------------------+-------------------------------------
Reporter: Trent Holliday | Owner:
| amansharma612
Type: Bug | Status: assigned
Component: contrib.postgres | Version: 4.2
Severity: Normal | Resolution:
Keywords: | Triage Stage:
| Unreviewed
Has patch: 1 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
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Comment (by Trent Holliday):
Thanks for the patch amansharma612.
The proposed changes have the potential for issues when querying against
the range, if the base `DecimalField` for the range is instantiated with
`max_digits` and `decimal_places`. When attempting to query using the
`__contains` with a decimal that exceeds the fields precision you get the
following error:
{{{
NumericValueOutOfRange: numeric field overflow
DETAIL: A field with precision 5, scale 2 must round to an absolute value
less than 10^3.
File "django/db/backends/utils.py", line 89, in _execute
return self.cursor.execute(sql, params)
DataError: numeric field overflow
DETAIL: A field with precision 5, scale 2 must round to an absolute value
less than 10^3.
}}}
This is something we are doing in a custom `DecimalRangeField` so that we
can limit the values entered and get good form validation. We currently
have a workaround in place where we implement a custom lookup that casts
the value while ignoring the base fields precision.
Our current workaround which gets registered to our custom decimal range
field:
{{{
class _UnboundedDecimalField(models.DecimalField):
def db_type(self, connection):
return "numeric"
class UnboundedDecimalRangeContains(RangeContains):
def get_prep_lookup(self):
if not isinstance(self.rhs, (list, tuple, Range)):
return Cast(self.rhs, output_field=_UnboundedDecimalField())
return super().get_prep_lookup()
}}}
I recognize this is probably out of scope for Django since the Django
provided decimal range field would not have this problem. However it does
lead to unexpected issues when extending the provided field and
implementing that precision. One possible way to avoid this would be to
always have the decimal range field cast the value in the contains lookup
as the more generic `numeric` to avoid the precision error when querying
against the range.
--
Ticket URL: <https://code.djangoproject.com/ticket/36031#comment:7>
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