Method only_expr

datafusion/expr/src/logical_plan/plan.rs:1194–1202

(&self, mut expr: Vec<Expr>)

    /// Helper for [Self::with_new_exprs] to use when exactly one expression is expected.
    #[inline]
    fn only_expr(&self, mut expr: Vec<Expr>) -> Result<Expr> {
        assert_eq_or_internal_err!(
            expr.len(),
            1,
            "{self:?} should have exactly one expr, got {:?}",
            &expr
        );
        Ok(expr.remove(0))
    }

    /// Helper for [Self::with_new_exprs] to use when exactly one input is expected.
    #[inline]