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From hbdeshmukh <...@git.apache.org>
Subject [GitHub] incubator-quickstep issue #224: Fix a bug in PackedPayloadHashTable
Date Wed, 29 Mar 2017 19:47:52 GMT
Github user hbdeshmukh commented on the issue:

    https://github.com/apache/incubator-quickstep/pull/224
  
    @zuyu There is a threshold to decide whether we perform the group by aggregation in a
partitioned way or not. If the estimated number of groups (provided by the optimizer) is greater
than the threshold, we go for partitioned aggregation. In TPC-H Q10 for SF100 the estimate
comes out to be 50k and the default threshold is also 50k. Therefore we were not able to perform
parallel partitioned aggregation. When I tried to force the aggregation to be partitioned,
the addressed bug was exposed. With the changes in this PR, now the aggregation is partitioned
and hence the performance improvement. 


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