Accumulo
  1. Accumulo
  2. ACCUMULO-2915

Avoid copying all Mutations when using a TabletServerBatchWriter

    Details

    • Type: Improvement Improvement
    • Status: Open
    • Priority: Major Major
    • Resolution: Unresolved
    • Affects Version/s: 1.5.0, 1.5.1, 1.6.0, 1.6.1, 1.7.0
    • Fix Version/s: 1.8.0
    • Component/s: client
    • Labels:
      None

      Description

      Currently in the TabletServerBatchWriter, the following behavior is exhibited:

          // create a copy of mutation so that after this method returns the user
          // is free to reuse the mutation object, like calling readFields... this
          // is important for the case where a mutation is passed from map to reduce
          // to batch writer... the map reduce code will keep passing the same mutation
          // object into the reduce method
          m = new Mutation(m);
          
          totalMemUsed += m.estimatedMemoryUsed();
          mutations.addMutation(table, m);
          totalAdded++;
      

      This means all data is copied twice when writing. The logic for doing this is a bit dubious, since not all clients are going to be subject to MapReduce's use of references.

      It'd be good if we provided users with a way of signaling that there's no need to copy the mutation payload. Josh Elser suggested creating something akin to an ImmutableMutation, which help avoid some of the fears the batchwriter attempts to defend against.

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            • Assignee:
              William Slacum
              Reporter:
              William Slacum
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              Dates

              • Created:
                Updated:

                Development