Function extract_equi_link

nodedb-sql/src/planner/cte.rs:435–469

Extract `(collection_field, cte_field)` from an equi-join ON clause.

(
    expr: &ast::Expr,
    real_alias: &str,
    cte_alias: &str,
)

/// Extract `(collection_field, cte_field)` from an equi-join ON clause.
fn extract_equi_link(
    expr: &ast::Expr,
    real_alias: &str,
    cte_alias: &str,
) -> Option<(String, String)> {
    match expr {
        ast::Expr::BinaryOp {
            left,
            op: ast::BinaryOperator::Eq,
            right,
        } => {
            let left_parts = extract_qualified_column(left)?;
            let right_parts = extract_qualified_column(right)?;

            if left_parts.0.eq_ignore_ascii_case(real_alias)
                && right_parts.0.eq_ignore_ascii_case(cte_alias)
            {
                Some((left_parts.1, right_parts.1))
            } else if right_parts.0.eq_ignore_ascii_case(real_alias)
                && left_parts.0.eq_ignore_ascii_case(cte_alias)
            {
                Some((right_parts.1, left_parts.1))
            } else {
                None
            }
        }
        ast::Expr::BinaryOp {
            left,
            op: ast::BinaryOperator::And,
            right,
        } => extract_equi_link(left, real_alias, cte_alias)
            .or_else(|| extract_equi_link(right, real_alias, cte_alias)),
        _ => None,
    }
}

fn extract_qualified_column(expr: &ast::Expr) -> Option<(String, String)> {
    match expr {