Class _ColumnMetrics

lib/sqlalchemy/sql/base.py:1733–1774

class _ColumnMetrics(Generic[_COL_co]):
    __slots__ = ("column",)

    column: _COL_co

    def __init__(
        self, collection: ColumnCollection[Any, _COL_co], col: _COL_co
    ) -> None:
        self.column = col

        # proxy_index being non-empty means it was initialized.
        # so we need to update it
        pi = collection._proxy_index
        if pi:
            for eps_col in col._expanded_proxy_set:
                pi[eps_col].add(self)

    def get_expanded_proxy_set(self) -> FrozenSet[ColumnElement[Any]]:
        return self.column._expanded_proxy_set

    def dispose(self, collection: ColumnCollection[_COLKEY, _COL_co]) -> None:
        pi = collection._proxy_index
        if not pi:
            return
        for col in self.column._expanded_proxy_set:
            colset = pi.get(col, None)
            if colset:
                colset.discard(self)
            if colset is not None and not colset:
                del pi[col]

    def embedded(
        self,
        target_set: Union[
            Set[ColumnElement[Any]], FrozenSet[ColumnElement[Any]]
        ],
    ) -> bool:
        expanded_proxy_set = self.column._expanded_proxy_set
        for t in target_set.difference(expanded_proxy_set):
            if not expanded_proxy_set.intersection(_expand_cloned([t])):
                return False
        return True


class ColumnCollection(Generic[_COLKEY, _COL_co]):