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from typing import List, Optional, Tuple, Union
from django.contrib.postgres.fields import HStoreField as DjangoHStoreField
from django.db.models.expressions import Expression
from django.db.models.fields import Field
class HStoreField(DjangoHStoreField):
"""Improved version of Django's :see:HStoreField that adds support for
database-level constraints.
Notes:
- For the implementation of uniqueness, see the
custom database back-end.
"""
def __init__(
self,
*args,
uniqueness: Optional[List[Union[str, Tuple[str, ...]]]] = None,
required: Optional[List[str]] = None,
**kwargs
):
"""Initializes a new instance of :see:HStoreField.
Arguments:
uniqueness:
List of keys to enforce as unique. Use tuples
to enforce multiple keys together to be unique.
required:
List of keys that should be enforced as required.
"""
super(HStoreField, self).__init__(*args, **kwargs)
self.uniqueness = uniqueness
self.required = required
def get_prep_value(self, value):
"""Override the base class so it doesn't cast all values to strings.
psqlextra supports expressions in hstore fields, so casting all
values to strings is a bad idea.
"""
value = Field.get_prep_value(self, value)
if isinstance(value, dict):
prep_value = {}
for key, val in value.items():
if isinstance(val, Expression):
prep_value[key] = val
elif val is not None:
prep_value[key] = str(val)
else:
prep_value[key] = val
value = prep_value
if isinstance(value, list):
value = [str(item) for item in value]
return value
def deconstruct(self):
"""Gets the values to pass to :see:__init__ when re-creating this
object."""
name, path, args, kwargs = super(HStoreField, self).deconstruct()
if self.uniqueness is not None:
kwargs["uniqueness"] = self.uniqueness
if self.required is not None:
kwargs["required"] = self.required
return name, path, args, kwargs
|
