base.py 文件源码

def check_constraints(self, table_names=None):
        """Check rows in tables for invalid foreign key references

        Checks each table name in `table_names` for rows with invalid foreign
        key references. This method is intended to be used in conjunction with
        `disable_constraint_checking()` and `enable_constraint_checking()`, to
        determine if rows with invalid references were entered while
        constraint checks were off.

        Raises an IntegrityError on the first invalid foreign key reference
        encountered (if any) and provides detailed information about the
        invalid reference in the error message.

        Backends can override this method if they can more directly apply
        constraint checking (e.g. via "SET CONSTRAINTS ALL IMMEDIATE")
        """
        ref_query = """
            SELECT REFERRING.`{0}`, REFERRING.`{1}` FROM `{2}` as REFERRING
            LEFT JOIN `{3}` as REFERRED
            ON (REFERRING.`{4}` = REFERRED.`{5}`)
            WHERE REFERRING.`{6}` IS NOT NULL AND REFERRED.`{7}` IS NULL"""
        cursor = self.cursor()
        if table_names is None:
            table_names = self.introspection.table_names(cursor)
        for table_name in table_names:
            primary_key_column_name = \
                self.introspection.get_primary_key_column(cursor, table_name)
            if not primary_key_column_name:
                continue
            key_columns = self.introspection.get_key_columns(cursor,
                                                             table_name)
            for column_name, referenced_table_name, referenced_column_name \
                    in key_columns:
                cursor.execute(ref_query.format(primary_key_column_name,
                                                column_name, table_name,
                                                referenced_table_name,
                                                column_name,
                                                referenced_column_name,
                                                column_name,
                                                referenced_column_name))
                for bad_row in cursor.fetchall():
                    msg = ("The row in table '{0}' with primary key '{1}' has "
                           "an invalid foreign key: {2}.{3} contains a value "
                           "'{4}' that does not have a corresponding value in "
                           "{5}.{6}.".format(table_name, bad_row[0],
                                             table_name, column_name,
                                             bad_row[1], referenced_table_name,
                                             referenced_column_name))
                    raise utils.IntegrityError(msg)