Function find_join_exprs

datafusion/expr/src/utils.rs:1264–1280

Looks for correlating expressions: for example, a binary expression with one field from the subquery, and one not in the subquery (closed upon from outer scope) # Arguments `exprs` - List of expressions that may or may not be joins # Return value Tuple of (expressions containing joins, remaining non-join expressions)

(exprs: Vec<&Expr>)

///
/// Tuple of (expressions containing joins, remaining non-join expressions)
pub fn find_join_exprs(exprs: Vec<&Expr>) -> Result<(Vec<Expr>, Vec<Expr>)> {
    let mut joins = vec![];
    let mut others = vec![];
    for filter in exprs.into_iter() {
        // If the expression contains correlated predicates, add it to join filters
        if filter.contains_outer() {
            if !matches!(filter, Expr::BinaryExpr(BinaryExpr{ left, op: Operator::Eq, right }) if left.eq(right))
            {
                joins.push(strip_outer_reference((*filter).clone()));
            }
        } else {
            others.push((*filter).clone());
        }
    }

    Ok((joins, others))
}

/// Returns the first (and only) element in a slice, or an error
///