gistfile1.rs

fn join_step<'a>(join: &'a Join, ix: usize, inputs: &[&'a Relation], state: &mut Vec<&'a Value>, index: &mut BTreeSet<Vec<Value>>) {
    if ix == join.sources.len() {
        index.insert(join.select.select(&state[..]));
    } else {
        match join.sources[ix] {
            JoinSource::Relation{input} => {
                for values in inputs[input].index.iter() {
                    push_all(state, values);
                    if join.constraints[ix].iter().all(|constraint| constraint.is_satisfied_by(&state[..])) {
                        join_step(join, ix+1, inputs, state, index)
                    }
                    pop_all(state, values);
                }
            }
            JoinSource::Primitive{ref primitive, ref arguments, ..} => {
                for values in primitive.eval_from_join(&arguments[..], &state[..]).into_iter() {
                    // promise the borrow checker that we will pop values before we exit this scope
                    let values = unsafe { ::std::mem::transmute::<&Vec<Value>, &'a Vec<Value>>(&values) };
                    push_all(state, values);
                    if join.constraints[ix].iter().all(|constraint| constraint.is_satisfied_by(&state[..])) {
                        join_step(join, ix+1, inputs, state, index)
                    }
                    pop_all(state, values);
                }
            }
        }
    }
}