Source code for django.db.migrations.operations.fields

from __future__ import unicode_literals

from django.db.models.fields import NOT_PROVIDED
from django.utils import six
from django.utils.functional import cached_property

from .base import Operation


[docs]class AddField(Operation): """ Adds a field to a model. """ def __init__(self, model_name, name, field, preserve_default=True): self.model_name = model_name self.name = name self.field = field self.preserve_default = preserve_default @cached_property def name_lower(self): return self.name.lower() @cached_property def model_name_lower(self): return self.model_name.lower() 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.append((self.name, field)) state.reload_model(app_label, self.model_name_lower) 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) def references_model(self, name, app_label=None): return name.lower() == self.model_name_lower def references_field(self, model_name, name, app_label=None): return self.references_model(model_name) and name.lower() == self.name_lower
[docs]class RemoveField(Operation): """ Removes a field from a model. """ def __init__(self, model_name, name): self.model_name = model_name self.name = name @cached_property def name_lower(self): return self.name.lower() @cached_property def model_name_lower(self): return self.model_name.lower() def deconstruct(self): kwargs = { 'model_name': self.model_name, 'name': self.name, } return ( self.__class__.__name__, [], kwargs ) def state_forwards(self, app_label, state): new_fields = [] for name, instance in state.models[app_label, self.model_name_lower].fields: if name != self.name: new_fields.append((name, instance)) state.models[app_label, self.model_name_lower].fields = new_fields state.reload_model(app_label, self.model_name_lower) 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) def references_model(self, name, app_label=None): return name.lower() == self.model_name_lower def references_field(self, model_name, name, app_label=None): return self.references_model(model_name) and name.lower() == self.name_lower
[docs]class AlterField(Operation): """ Alters 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.model_name = model_name self.name = name self.field = field self.preserve_default = preserve_default @cached_property def name_lower(self): return self.name.lower() @cached_property def model_name_lower(self): return self.model_name.lower() 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 state.models[app_label, self.model_name_lower].fields = [ (n, field if n == self.name else f) for n, f in state.models[app_label, self.model_name_lower].fields ] state.reload_model(app_label, self.model_name_lower) 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 the field is a relatedfield with an unresolved rel.to, just # set it equal to the other field side. Bandaid fix for AlterField # migrations that are part of a RenameModel change. if from_field.remote_field and from_field.remote_field.model: if isinstance(from_field.remote_field.model, six.string_types): from_field.remote_field.model = to_field.remote_field.model elif to_field.remote_field and isinstance(to_field.remote_field.model, six.string_types): to_field.remote_field.model = from_field.remote_field.model 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) def references_model(self, name, app_label=None): return name.lower() == self.model_name_lower def references_field(self, model_name, name, app_label=None): return self.references_model(model_name) and name.lower() == self.name_lower
[docs]class RenameField(Operation): """ Renames a field on the model. Might affect db_column too. """ def __init__(self, model_name, old_name, new_name): self.model_name = model_name self.old_name = old_name self.new_name = new_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() @cached_property def model_name_lower(self): return self.model_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): # Rename the field state.models[app_label, self.model_name_lower].fields = [ (self.new_name if n == self.old_name else n, f) for n, f in state.models[app_label, self.model_name_lower].fields ] # Fix index/unique_together to refer to the new field options = state.models[app_label, self.model_name_lower].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] ] state.reload_model(app_label, self.model_name_lower) 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) def references_model(self, name, app_label=None): return name.lower() == self.model_name_lower def references_field(self, model_name, name, app_label=None): return self.references_model(model_name) and ( name.lower() == self.old_name_lower or name.lower() == self.new_name_lower )
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