expression.py 文件源码

def distinct(self, *expr):
        """Return a new select() construct which will apply DISTINCT to its
        columns clause.

        :param \*expr: optional column expressions.  When present,
         the Postgresql dialect will render a ``DISTINCT ON (<expressions>>)``
         construct.

        """
        if expr:
            expr = [_literal_as_text(e) for e in expr]
            if isinstance(self._distinct, list):
                self._distinct = self._distinct + expr
            else:
                self._distinct = expr
        else:
            self._distinct = True