Function expand_leaf

crates/expr/src/rls.rs:448–472

Replaces the leaf node determined by `table_id` and `alias` with the subtree `with`. Ensures the expanded tree stays left deep.

(expr: RelExpr, table_id: TableId, alias: &str, with: &RelExpr)

/// Replaces the leaf node determined by `table_id` and `alias` with the subtree `with`.
/// Ensures the expanded tree stays left deep.
fn expand_leaf(expr: RelExpr, table_id: TableId, alias: &str, with: &RelExpr) -> RelExpr {
    let ok = |relvar: &Relvar| relvar.schema.table_id == table_id && relvar.alias.as_ref() == alias;
    match expr {
        RelExpr::RelVar(relvar, ..) if ok(&relvar) => with.clone(),
        RelExpr::RelVar(..) => expr,
        RelExpr::Select(input, expr) => RelExpr::Select(Box::new(expand_leaf(*input, table_id, alias, with)), expr),
        RelExpr::LeftDeepJoin(join) if ok(&join.rhs) => extend_lhs(with.clone(), *join.lhs),
        RelExpr::LeftDeepJoin(LeftDeepJoin { lhs, rhs }) => RelExpr::LeftDeepJoin(LeftDeepJoin {
            lhs: Box::new(expand_leaf(*lhs, table_id, alias, with)),
            rhs,
        }),
        RelExpr::EqJoin(join, a, b) if ok(&join.rhs) => RelExpr::Select(
            Box::new(extend_lhs(with.clone(), *join.lhs)),
            Expr::BinOp(BinOp::Eq, Box::new(Expr::Field(a)), Box::new(Expr::Field(b))),
        ),
        RelExpr::EqJoin(LeftDeepJoin { lhs, rhs }, a, b) => RelExpr::EqJoin(
            LeftDeepJoin {
                lhs: Box::new(expand_leaf(*lhs, table_id, alias, with)),
                rhs,
            },
            a,
            b,
        ),
    }
}

#[cfg(test)]
mod tests {