Method _make_proxy

lib/sqlalchemy/sql/elements.py:1657–1700

Create a new :class:`_expression.ColumnElement` representing this :class:`_expression.ColumnElement` as it appears in the select list of a descending selectable.

(
        self,
        selectable: FromClause,
        *,
        primary_key: ColumnSet,
        foreign_keys: Set[KeyedColumnElement[Any]],
        name: Optional[str] = None,
        key: Optional[str] = None,
        name_is_truncatable: bool = False,
        compound_select_cols: Optional[Sequence[ColumnElement[Any]]] = None,
        **kw: Any,
    )

            return None

    def _make_proxy(
        self,
        selectable: FromClause,
        *,
        primary_key: ColumnSet,
        foreign_keys: Set[KeyedColumnElement[Any]],
        name: Optional[str] = None,
        key: Optional[str] = None,
        name_is_truncatable: bool = False,
        compound_select_cols: Optional[Sequence[ColumnElement[Any]]] = None,
        **kw: Any,
    ) -> typing_Tuple[str, ColumnClause[_T]]:
        """Create a new :class:`_expression.ColumnElement` representing this
        :class:`_expression.ColumnElement` as it appears in the select list of
        a descending selectable.

        """
        if name is None:
            name = self._anon_name_label
            if key is None:
                key = self._proxy_key
        else:
            key = name

        assert key is not None

        co: ColumnClause[_T] = ColumnClause(
            (
                coercions.expect(roles.TruncatedLabelRole, name)
                if name_is_truncatable
                else name
            ),
            type_=getattr(self, "type", None),
            _selectable=selectable,
        )

        co._propagate_attrs = selectable._propagate_attrs
        if compound_select_cols:
            co._proxies = list(compound_select_cols)
        else:
            co._proxies = [self]
        if selectable._is_clone_of is not None:
            co._is_clone_of = selectable._is_clone_of.columns.get(key)
        return key, co

    def cast(self, type_: _TypeEngineArgument[_OPT]) -> Cast[_OPT]:
        """Produce a type cast, i.e. ``CAST(<expression> AS <type>)``.