Method _validate_expression

python/pathway/internals/groupbys.py:248–272

(self, expression: expr.ColumnExpression)

        return result

    def _validate_expression(self, expression: expr.ColumnExpression):
        for dep in expression._dependencies_above_reducer():
            if (
                not isinstance(dep._table, thisclass.ThisMetaclass)  # allow for ix
                and dep.to_column_expression()._to_original()._to_internal()
                not in self._grouping_columns
            ):
                raise ValueError(
                    f"You cannot use {dep.to_column_expression()} in this reduce statement.\n"
                    + f"Make sure that {dep.to_column_expression()} is used in a groupby or wrap it with a reducer, "
                    + f"e.g. pw.reducers.count({dep.to_column_expression()})"
                )

        for dep in expression._dependencies_below_reducer():
            if (
                self._joinable_to_group._universe
                != dep.to_column_expression()._column.universe
            ):
                raise ValueError(
                    f"You cannot use {dep.to_column_expression()} in this context."
                    + " Its universe is different than the universe of the table the method"
                    + " was called on. You can use <table1>.with_universe_of(<table2>)"
                    + " to assign universe of <table2> to <table1> if you're sure their"
                    + " sets of keys are equal."
                )

    @lru_cache
    def _operator_dependencies(self) -> StableSet[table.Table]: