Even Faster Unnest

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Unnest is a common operation in Facebook’s daily Presto workload. It converts an ARRAY, MAP, or ROW into a flat relation. Its original implementation used deep copy all the time and was very inefficient. In Unnest Operator Performance Enhancement with Dictionary Blocks, the author improved the Unnest operator by up to 10x in CPU and…

5 design choices—and 1 weird trick — to get 2x efficiency gains in Presto repartitioning

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We like Presto. We like it a lot — so much we want to make it better in every way. Here’s an example: we just optimized the PartitionedOutputOperator. It’s now 2-3x more CPU efficient, which, when measured against Facebook’s production workload, translates to 6% gains overall. That’s huge. The optimized repartitioning is in use on…