def get_pk_constraint(self, connection, table_name, schema=None, **kw):
        """
        Return information about the primary key constraint on `table_name`.

        Overrides interface
        :meth:`~sqlalchemy.engine.interfaces.Dialect.get_pk_constraint`.
        """
        constraints = self._get_redshift_constraints(connection, table_name,
                                                     schema, **kw)
        pk_constraints = [c for c in constraints if c.contype == 'p']
        if not pk_constraints:
            return {'constrained_columns': [], 'name': ''}
        pk_constraint = pk_constraints[0]
        m = PRIMARY_KEY_RE.match(pk_constraint.condef)
        colstring = m.group('columns')
        constrained_columns = SQL_IDENTIFIER_RE.findall(colstring)
        return {
            'constrained_columns': constrained_columns,
            'name': pk_constraint.conname,
        }
Return information about the primary key constraint on `table_name`.

        Overrides interface
        :meth:`~sqlalchemy.engine.interfaces.Dialect.get_pk_constraint`.