Function find_owning_input

datafusion/optimizer/src/extract_leaf_expressions.rs:272–287

Given an expression, returns the index of the input whose columns fully cover the expression's column references. Returns `None` if the expression references columns from multiple inputs or if multiple inputs match (ambiguous, e.g. unqualified columns present in both sides of a join).

(
    expr: &Expr,
    input_column_sets: &[std::collections::HashSet<ColumnReference>],
)

/// or if multiple inputs match (ambiguous, e.g. unqualified columns present
/// in both sides of a join).
fn find_owning_input(
    expr: &Expr,
    input_column_sets: &[std::collections::HashSet<ColumnReference>],
) -> Option<usize> {
    let mut found = None;
    for (idx, cols) in input_column_sets.iter().enumerate() {
        if has_all_column_refs(expr, cols) {
            if found.is_some() {
                // Ambiguous — multiple inputs match
                return None;
            }
            found = Some(idx);
        }
    }
    found
}

/// Walks an expression tree top-down, extracting `MoveTowardsLeafNodes`
/// sub-expressions and routing each to the correct per-input extractor.