Method single_input

src/expr/src/relation/join_input_mapper.rs:238–246

Returns the index of the only input referenced in the given expression.

(&self, expr: &impl Columns)

    /// Returns the index of the only input referenced in the given expression.
    pub fn single_input(&self, expr: &impl Columns) -> Option<usize> {
        let mut inputs = self.lookup_inputs(expr);
        if let Some(first_input) = inputs.next() {
            if inputs.next().is_none() {
                return Some(first_input);
            }
        }
        None
    }

    /// Returns whether the given expr refers to columns of only the `index`th input.
    pub fn is_localized(&self, expr: &impl Columns, index: usize) -> bool {