flow::compute::render::reduce

Function eval_distinct_core

Source 
fn eval_distinct_core(
    arrange: RwLockReadGuard<'_, Arrangement>,
    kv: impl IntoIterator<Item = ((Row, Row), i64, i64)>,
    now: i64,
    err_collector: &ErrCollector,
) -> Vec<((Row, Row), i64, i64)>
Expand description

return distinct rows(distinct by row’s key) from the input, but do not update the arrangement

if the same key already exist, we only preserve the oldest value(It make sense for distinct input over key)