from django.db.backends.base.schema import BaseDatabaseSchemaEditor from django.db.models import NOT_PROVIDED class DatabaseSchemaEditor(BaseDatabaseSchemaEditor): sql_rename_table = "RENAME TABLE %(old_table)s TO %(new_table)s" sql_alter_column_null = "MODIFY %(column)s %(type)s NULL" sql_alter_column_not_null = "MODIFY %(column)s %(type)s NOT NULL" sql_alter_column_type = "MODIFY %(column)s %(type)s" # No 'CASCADE' which works as a no-op in MySQL but is undocumented sql_delete_column = "ALTER TABLE %(table)s DROP COLUMN %(column)s" sql_rename_column = "ALTER TABLE %(table)s CHANGE %(old_column)s %(new_column)s %(type)s" sql_delete_unique = "ALTER TABLE %(table)s DROP INDEX %(name)s" sql_delete_fk = "ALTER TABLE %(table)s DROP FOREIGN KEY %(name)s" sql_delete_index = "DROP INDEX %(name)s ON %(table)s" sql_create_pk = "ALTER TABLE %(table)s ADD CONSTRAINT %(name)s PRIMARY KEY (%(columns)s)" sql_delete_pk = "ALTER TABLE %(table)s DROP PRIMARY KEY" def quote_value(self, value): self.connection.ensure_connection() quoted = self.connection.connection.escape(value, self.connection.connection.encoders) if isinstance(value, str): quoted = quoted.decode() return quoted def _is_limited_data_type(self, field): db_type = field.db_type(self.connection) return db_type is not None and db_type.lower() in self.connection._limited_data_types def skip_default(self, field): return self._is_limited_data_type(field) def add_field(self, model, field): super().add_field(model, field) # Simulate the effect of a one-off default. # field.default may be unhashable, so a set isn't used for "in" check. if self.skip_default(field) and field.default not in (None, NOT_PROVIDED): effective_default = self.effective_default(field) self.execute('UPDATE %(table)s SET %(column)s = %%s' % { 'table': self.quote_name(model._meta.db_table), 'column': self.quote_name(field.column), }, [effective_default]) def _field_should_be_indexed(self, model, field): create_index = super()._field_should_be_indexed(model, field) storage = self.connection.introspection.get_storage_engine( self.connection.cursor(), model._meta.db_table ) # No need to create an index for ForeignKey fields except if # db_constraint=False because the index from that constraint won't be # created. if (storage == "InnoDB" and create_index and field.get_internal_type() == 'ForeignKey' and field.db_constraint): return False return not self._is_limited_data_type(field) and create_index def _delete_composed_index(self, model, fields, *args): """ MySQL can remove an implicit FK index on a field when that field is covered by another index like a unique_together. "covered" here means that the more complex index starts like the simpler one. http://bugs.mysql.com/bug.php?id=37910 / Django ticket #24757 We check here before removing the [unique|index]_together if we have to recreate a FK index. """ first_field = model._meta.get_field(fields[0]) if first_field.get_internal_type() == 'ForeignKey': constraint_names = self._constraint_names(model, [first_field.column], index=True) if not constraint_names: self.execute(self._create_index_sql(model, [first_field], suffix="")) return super()._delete_composed_index(model, fields, *args) def _set_field_new_type_null_status(self, field, new_type): """ Keep the null property of the old field. If it has changed, it will be handled separately. """ if field.null: new_type += " NULL" else: new_type += " NOT NULL" return new_type def _alter_column_type_sql(self, model, old_field, new_field, new_type): new_type = self._set_field_new_type_null_status(old_field, new_type) return super()._alter_column_type_sql(model, old_field, new_field, new_type) def _rename_field_sql(self, table, old_field, new_field, new_type): new_type = self._set_field_new_type_null_status(old_field, new_type) return super()._rename_field_sql(table, old_field, new_field, new_type)