Source code for django.db.migrations.operations.fields
from django.core.exceptions import FieldDoesNotExist
from django.db.models import NOT_PROVIDED
from django.utils.functional import cached_property
from .base import Operation
from .utils import field_is_referenced, field_references, get_references
class FieldOperation(Operation):
def __init__(self, model_name, name, field=None):
self.model_name = model_name
self.name = name
self.field = field
@cached_property
def model_name_lower(self):
return self.model_name.lower()
@cached_property
def name_lower(self):
return self.name.lower()
def is_same_model_operation(self, operation):
return self.model_name_lower == operation.model_name_lower
def is_same_field_operation(self, operation):
return self.is_same_model_operation(operation) and self.name_lower == operation.name_lower
def references_model(self, name, app_label):
name_lower = name.lower()
if name_lower == self.model_name_lower:
return True
if self.field:
return bool(field_references(
(app_label, self.model_name_lower), self.field, (app_label, name_lower)
))
return False
def references_field(self, model_name, name, app_label):
model_name_lower = model_name.lower()
# Check if this operation locally references the field.
if model_name_lower == self.model_name_lower:
if name == self.name:
return True
elif self.field and hasattr(self.field, 'from_fields') and name in self.field.from_fields:
return True
# Check if this operation remotely references the field.
if self.field is None:
return False
return bool(field_references(
(app_label, self.model_name_lower),
self.field,
(app_label, model_name_lower),
name,
))
def reduce(self, operation, app_label):
return (
super().reduce(operation, app_label) or
not operation.references_field(self.model_name, self.name, app_label)
)
[docs]class AddField(FieldOperation):
"""Add a field to a model."""
def __init__(self, model_name, name, field, preserve_default=True):
self.preserve_default = preserve_default
super().__init__(model_name, name, field)
def deconstruct(self):
kwargs = {
'model_name': self.model_name,
'name': self.name,
'field': self.field,
}
if self.preserve_default is not True:
kwargs['preserve_default'] = self.preserve_default
return (
self.__class__.__name__,
[],
kwargs
)
def state_forwards(self, app_label, state):
# If preserve default is off, don't use the default for future state
if not self.preserve_default:
field = self.field.clone()
field.default = NOT_PROVIDED
else:
field = self.field
state.models[app_label, self.model_name_lower].fields[self.name] = field
# Delay rendering of relationships if it's not a relational field
delay = not field.is_relation
state.reload_model(app_label, self.model_name_lower, delay=delay)
def database_forwards(self, app_label, schema_editor, from_state, to_state):
to_model = to_state.apps.get_model(app_label, self.model_name)
if self.allow_migrate_model(schema_editor.connection.alias, to_model):
from_model = from_state.apps.get_model(app_label, self.model_name)
field = to_model._meta.get_field(self.name)
if not self.preserve_default:
field.default = self.field.default
schema_editor.add_field(
from_model,
field,
)
if not self.preserve_default:
field.default = NOT_PROVIDED
def database_backwards(self, app_label, schema_editor, from_state, to_state):
from_model = from_state.apps.get_model(app_label, self.model_name)
if self.allow_migrate_model(schema_editor.connection.alias, from_model):
schema_editor.remove_field(from_model, from_model._meta.get_field(self.name))
def describe(self):
return "Add field %s to %s" % (self.name, self.model_name)
@property
def migration_name_fragment(self):
return '%s_%s' % (self.model_name_lower, self.name_lower)
def reduce(self, operation, app_label):
if isinstance(operation, FieldOperation) and self.is_same_field_operation(operation):
if isinstance(operation, AlterField):
return [
AddField(
model_name=self.model_name,
name=operation.name,
field=operation.field,
),
]
elif isinstance(operation, RemoveField):
return []
elif isinstance(operation, RenameField):
return [
AddField(
model_name=self.model_name,
name=operation.new_name,
field=self.field,
),
]
return super().reduce(operation, app_label)
[docs]class RemoveField(FieldOperation):
"""Remove a field from a model."""
def deconstruct(self):
kwargs = {
'model_name': self.model_name,
'name': self.name,
}
return (
self.__class__.__name__,
[],
kwargs
)
def state_forwards(self, app_label, state):
model_state = state.models[app_label, self.model_name_lower]
old_field = model_state.fields.pop(self.name)
# Delay rendering of relationships if it's not a relational field
delay = not old_field.is_relation
state.reload_model(app_label, self.model_name_lower, delay=delay)
def database_forwards(self, app_label, schema_editor, from_state, to_state):
from_model = from_state.apps.get_model(app_label, self.model_name)
if self.allow_migrate_model(schema_editor.connection.alias, from_model):
schema_editor.remove_field(from_model, from_model._meta.get_field(self.name))
def database_backwards(self, app_label, schema_editor, from_state, to_state):
to_model = to_state.apps.get_model(app_label, self.model_name)
if self.allow_migrate_model(schema_editor.connection.alias, to_model):
from_model = from_state.apps.get_model(app_label, self.model_name)
schema_editor.add_field(from_model, to_model._meta.get_field(self.name))
def describe(self):
return "Remove field %s from %s" % (self.name, self.model_name)
@property
def migration_name_fragment(self):
return 'remove_%s_%s' % (self.model_name_lower, self.name_lower)
def reduce(self, operation, app_label):
from .models import DeleteModel
if isinstance(operation, DeleteModel) and operation.name_lower == self.model_name_lower:
return [operation]
return super().reduce(operation, app_label)
[docs]class AlterField(FieldOperation):
"""
Alter a field's database column (e.g. null, max_length) to the provided
new field.
"""
def __init__(self, model_name, name, field, preserve_default=True):
self.preserve_default = preserve_default
super().__init__(model_name, name, field)
def deconstruct(self):
kwargs = {
'model_name': self.model_name,
'name': self.name,
'field': self.field,
}
if self.preserve_default is not True:
kwargs['preserve_default'] = self.preserve_default
return (
self.__class__.__name__,
[],
kwargs
)
def state_forwards(self, app_label, state):
if not self.preserve_default:
field = self.field.clone()
field.default = NOT_PROVIDED
else:
field = self.field
model_state = state.models[app_label, self.model_name_lower]
model_state.fields[self.name] = field
# TODO: investigate if old relational fields must be reloaded or if it's
# sufficient if the new field is (#27737).
# Delay rendering of relationships if it's not a relational field and
# not referenced by a foreign key.
delay = (
not field.is_relation and
not field_is_referenced(
state, (app_label, self.model_name_lower), (self.name, field),
)
)
state.reload_model(app_label, self.model_name_lower, delay=delay)
def database_forwards(self, app_label, schema_editor, from_state, to_state):
to_model = to_state.apps.get_model(app_label, self.model_name)
if self.allow_migrate_model(schema_editor.connection.alias, to_model):
from_model = from_state.apps.get_model(app_label, self.model_name)
from_field = from_model._meta.get_field(self.name)
to_field = to_model._meta.get_field(self.name)
if not self.preserve_default:
to_field.default = self.field.default
schema_editor.alter_field(from_model, from_field, to_field)
if not self.preserve_default:
to_field.default = NOT_PROVIDED
def database_backwards(self, app_label, schema_editor, from_state, to_state):
self.database_forwards(app_label, schema_editor, from_state, to_state)
def describe(self):
return "Alter field %s on %s" % (self.name, self.model_name)
@property
def migration_name_fragment(self):
return 'alter_%s_%s' % (self.model_name_lower, self.name_lower)
def reduce(self, operation, app_label):
if isinstance(operation, RemoveField) and self.is_same_field_operation(operation):
return [operation]
elif isinstance(operation, RenameField) and self.is_same_field_operation(operation):
return [
operation,
AlterField(
model_name=self.model_name,
name=operation.new_name,
field=self.field,
),
]
return super().reduce(operation, app_label)
[docs]class RenameField(FieldOperation):
"""Rename a field on the model. Might affect db_column too."""
def __init__(self, model_name, old_name, new_name):
self.old_name = old_name
self.new_name = new_name
super().__init__(model_name, old_name)
@cached_property
def old_name_lower(self):
return self.old_name.lower()
@cached_property
def new_name_lower(self):
return self.new_name.lower()
def deconstruct(self):
kwargs = {
'model_name': self.model_name,
'old_name': self.old_name,
'new_name': self.new_name,
}
return (
self.__class__.__name__,
[],
kwargs
)
def state_forwards(self, app_label, state):
model_state = state.models[app_label, self.model_name_lower]
# Rename the field
fields = model_state.fields
try:
found = fields.pop(self.old_name)
except KeyError:
raise FieldDoesNotExist(
"%s.%s has no field named '%s'" % (app_label, self.model_name, self.old_name)
)
fields[self.new_name] = found
for field in fields.values():
# Fix from_fields to refer to the new field.
from_fields = getattr(field, 'from_fields', None)
if from_fields:
field.from_fields = tuple([
self.new_name if from_field_name == self.old_name else from_field_name
for from_field_name in from_fields
])
# Fix index/unique_together to refer to the new field
options = model_state.options
for option in ('index_together', 'unique_together'):
if option in options:
options[option] = [
[self.new_name if n == self.old_name else n for n in together]
for together in options[option]
]
# Fix to_fields to refer to the new field.
delay = True
references = get_references(
state, (app_label, self.model_name_lower), (self.old_name, found),
)
for *_, field, reference in references:
delay = False
if reference.to:
remote_field, to_fields = reference.to
if getattr(remote_field, 'field_name', None) == self.old_name:
remote_field.field_name = self.new_name
if to_fields:
field.to_fields = tuple([
self.new_name if to_field_name == self.old_name else to_field_name
for to_field_name in to_fields
])
state.reload_model(app_label, self.model_name_lower, delay=delay)
def database_forwards(self, app_label, schema_editor, from_state, to_state):
to_model = to_state.apps.get_model(app_label, self.model_name)
if self.allow_migrate_model(schema_editor.connection.alias, to_model):
from_model = from_state.apps.get_model(app_label, self.model_name)
schema_editor.alter_field(
from_model,
from_model._meta.get_field(self.old_name),
to_model._meta.get_field(self.new_name),
)
def database_backwards(self, app_label, schema_editor, from_state, to_state):
to_model = to_state.apps.get_model(app_label, self.model_name)
if self.allow_migrate_model(schema_editor.connection.alias, to_model):
from_model = from_state.apps.get_model(app_label, self.model_name)
schema_editor.alter_field(
from_model,
from_model._meta.get_field(self.new_name),
to_model._meta.get_field(self.old_name),
)
def describe(self):
return "Rename field %s on %s to %s" % (self.old_name, self.model_name, self.new_name)
@property
def migration_name_fragment(self):
return 'rename_%s_%s_%s' % (
self.old_name_lower,
self.model_name_lower,
self.new_name_lower,
)
def references_field(self, model_name, name, app_label):
return self.references_model(model_name, app_label) and (
name.lower() == self.old_name_lower or
name.lower() == self.new_name_lower
)
def reduce(self, operation, app_label):
if (isinstance(operation, RenameField) and
self.is_same_model_operation(operation) and
self.new_name_lower == operation.old_name_lower):
return [
RenameField(
self.model_name,
self.old_name,
operation.new_name,
),
]
# Skip `FieldOperation.reduce` as we want to run `references_field`
# against self.new_name.
return (
super(FieldOperation, self).reduce(operation, app_label) or
not operation.references_field(self.model_name, self.new_name, app_label)
)
