postgresql.py 文件源码

def to_constraint(self, migration_context=None):
        if not util.sqla_100:
            raise NotImplementedError(
                "ExcludeConstraint not supported until SQLAlchemy 1.0")
        if self._orig_constraint is not None:
            return self._orig_constraint
        schema_obj = schemaobj.SchemaObjects(migration_context)
        t = schema_obj.table(self.table_name, schema=self.schema)
        excl = ExcludeConstraint(
            *self.elements,
            name=self.constraint_name,
            where=self.where,
            **self.kw
        )
        for expr, name, oper in excl._render_exprs:
            t.append_column(Column(name, NULLTYPE))
        t.append_constraint(excl)
        return excl