import codecs import copy from decimal import Decimal from django.utils import six from django.apps.registry import Apps from django.db.backends.schema import BaseDatabaseSchemaEditor from django.db.models.fields.related import ManyToManyField class DatabaseSchemaEditor(BaseDatabaseSchemaEditor): sql_delete_table = "DROP TABLE %(table)s" sql_create_inline_fk = "REFERENCES %(to_table)s (%(to_column)s)" def quote_value(self, value): # Inner import to allow nice failure for backend if not present import _sqlite3 try: value = _sqlite3.adapt(value) except _sqlite3.ProgrammingError: pass # Manual emulation of SQLite parameter quoting if isinstance(value, type(True)): return str(int(value)) elif isinstance(value, (Decimal, float)): return str(value) elif isinstance(value, six.integer_types): return str(value) elif isinstance(value, six.string_types): return "'%s'" % six.text_type(value).replace("\'", "\'\'") elif value is None: return "NULL" elif isinstance(value, (bytes, bytearray, six.memoryview)): # Bytes are only allowed for BLOB fields, encoded as string # literals containing hexadecimal data and preceded by a single "X" # character: # value = b'\x01\x02' => value_hex = b'0102' => return X'0102' value = bytes(value) hex_encoder = codecs.getencoder('hex_codec') value_hex, _length = hex_encoder(value) # Use 'ascii' encoding for b'01' => '01', no need to use force_text here. return "X'%s'" % value_hex.decode('ascii') else: raise ValueError("Cannot quote parameter value %r of type %s" % (value, type(value))) def _remake_table(self, model, create_fields=[], delete_fields=[], alter_fields=[], override_uniques=None): """ Shortcut to transform a model from old_model into new_model """ # Work out the new fields dict / mapping body = dict((f.name, f) for f in model._meta.local_fields) # Since mapping might mix column names and default values, # its values must be already quoted. mapping = dict((f.column, self.quote_name(f.column)) for f in model._meta.local_fields) # This maps field names (not columns) for things like unique_together rename_mapping = {} # If any of the new or altered fields is introducing a new PK, # remove the old one restore_pk_field = None if any(f.primary_key for f in create_fields) or any(n.primary_key for o, n in alter_fields): for name, field in list(body.items()): if field.primary_key: field.primary_key = False restore_pk_field = field if field.auto_created: del body[name] del mapping[field.column] # Add in any created fields for field in create_fields: body[field.name] = field # If there's a default, insert it into the copy map if field.has_default(): mapping[field.column] = self.quote_value( self.effective_default(field) ) # Add in any altered fields for (old_field, new_field) in alter_fields: del body[old_field.name] del mapping[old_field.column] body[new_field.name] = new_field if old_field.null and not new_field.null: case_sql = "coalesce(%(col)s, %(default)s)" % { 'col': self.quote_name(old_field.column), 'default': self.quote_value(self.effective_default(new_field)) } mapping[new_field.column] = case_sql else: mapping[new_field.column] = self.quote_name(old_field.column) rename_mapping[old_field.name] = new_field.name # Remove any deleted fields for field in delete_fields: del body[field.name] del mapping[field.column] # Remove any implicit M2M tables if isinstance(field, ManyToManyField) and field.rel.through._meta.auto_created: return self.delete_model(field.rel.through) # Work inside a new app registry apps = Apps() # Provide isolated instances of the fields to the new model body # Instantiating the new model with an alternate db_table will alter # the internal references of some of the provided fields. body = copy.deepcopy(body) # Work out the new value of unique_together, taking renames into # account if override_uniques is None: override_uniques = [ [rename_mapping.get(n, n) for n in unique] for unique in model._meta.unique_together ] # Construct a new model for the new state meta_contents = { 'app_label': model._meta.app_label, 'db_table': model._meta.db_table + "__new", 'unique_together': override_uniques, 'apps': apps, } meta = type("Meta", tuple(), meta_contents) body['Meta'] = meta body['__module__'] = model.__module__ temp_model = type(model._meta.object_name, model.__bases__, body) # Create a new table with that format. We remove things from the # deferred SQL that match our table name, too self.deferred_sql = [x for x in self.deferred_sql if model._meta.db_table not in x] self.create_model(temp_model) # Copy data from the old table field_maps = list(mapping.items()) self.execute("INSERT INTO %s (%s) SELECT %s FROM %s" % ( self.quote_name(temp_model._meta.db_table), ', '.join(self.quote_name(x) for x, y in field_maps), ', '.join(y for x, y in field_maps), self.quote_name(model._meta.db_table), )) # Delete the old table self.delete_model(model, handle_autom2m=False) # Rename the new to the old self.alter_db_table(temp_model, temp_model._meta.db_table, model._meta.db_table) # Run deferred SQL on correct table for sql in self.deferred_sql: self.execute(sql.replace(temp_model._meta.db_table, model._meta.db_table)) self.deferred_sql = [] # Fix any PK-removed field if restore_pk_field: restore_pk_field.primary_key = True def delete_model(self, model, handle_autom2m=True): if handle_autom2m: super(DatabaseSchemaEditor, self).delete_model(model) else: # Delete the table (and only that) self.execute(self.sql_delete_table % { "table": self.quote_name(model._meta.db_table), }) def add_field(self, model, field): """ Creates a field on a model. Usually involves adding a column, but may involve adding a table instead (for M2M fields) """ # Special-case implicit M2M tables if isinstance(field, ManyToManyField) and field.rel.through._meta.auto_created: return self.create_model(field.rel.through) self._remake_table(model, create_fields=[field]) def remove_field(self, model, field): """ Removes a field from a model. Usually involves deleting a column, but for M2Ms may involve deleting a table. """ # M2M fields are a special case if isinstance(field, ManyToManyField): # For implicit M2M tables, delete the auto-created table if field.rel.through._meta.auto_created: self.delete_model(field.rel.through) # For explicit "through" M2M fields, do nothing # For everything else, remake. else: # It might not actually have a column behind it if field.db_parameters(connection=self.connection)['type'] is None: return self._remake_table(model, delete_fields=[field]) def _alter_field(self, model, old_field, new_field, old_type, new_type, old_db_params, new_db_params, strict=False): """Actually perform a "physical" (non-ManyToMany) field update.""" # Alter by remaking table self._remake_table(model, alter_fields=[(old_field, new_field)]) def alter_unique_together(self, model, old_unique_together, new_unique_together): """ Deals with a model changing its unique_together. Note: The input unique_togethers must be doubly-nested, not the single- nested ["foo", "bar"] format. """ self._remake_table(model, override_uniques=new_unique_together) def _alter_many_to_many(self, model, old_field, new_field, strict): """ Alters M2Ms to repoint their to= endpoints. """ if old_field.rel.through._meta.db_table == new_field.rel.through._meta.db_table: # The field name didn't change, but some options did; we have to propagate this altering. self._remake_table( old_field.rel.through, alter_fields=[( # We need the field that points to the target model, so we can tell alter_field to change it - # this is m2m_reverse_field_name() (as opposed to m2m_field_name, which points to our model) old_field.rel.through._meta.get_field_by_name(old_field.m2m_reverse_field_name())[0], new_field.rel.through._meta.get_field_by_name(new_field.m2m_reverse_field_name())[0], )], override_uniques=(new_field.m2m_field_name(), new_field.m2m_reverse_field_name()), ) return # Make a new through table self.create_model(new_field.rel.through) # Copy the data across self.execute("INSERT INTO %s (%s) SELECT %s FROM %s" % ( self.quote_name(new_field.rel.through._meta.db_table), ', '.join([ "id", new_field.m2m_column_name(), new_field.m2m_reverse_name(), ]), ', '.join([ "id", old_field.m2m_column_name(), old_field.m2m_reverse_name(), ]), self.quote_name(old_field.rel.through._meta.db_table), )) # Delete the old through table self.delete_model(old_field.rel.through)