Class AppendG

  • public class AppendG
    extends Lop
    TODO Additional compiler enhancements: 1) Partial Shuffle Elimination - Any full or aligned blocks could be directly output from the mappers to the result index. We only need to shuffle, sort and aggregate partial blocks. However, this requires piggybacking changes, i.e., (1) operations with multiple result indexes, and (2) multiple operations with the same result index. 2) Group Elimination for Append Chains - If we have chains of rappend each intermediate is shuffled and aggregated. This is unnecessary if all offsets are known in advance. We could directly pack all rappends in one GMR map-phase followed by one group and subsequent aggregate. However, this requires an n-ary rappend or group (with multiple inputs).