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      The initial IMPALA-3200 code added the ability for a grouping pre-aggregation to run with zero reservation, passing through all of the rows. However, this is a very low performance mode for aggregations that reduce their input a lot, since it forces everything to be sent over the network. We would be better off in most cases requiring more memory but not allowing perf to degrade so much.

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              • Assignee:
                tarmstrong Tim Armstrong
                Reporter:
                tarmstrong Tim Armstrong
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