[GitHub] peferron commented on issue #6889: [Proposal] Use bitmap iteration for filtered aggregators

[GitBox <gi...@apache.org>]

peferron commented on issue #6889: [Proposal] Use bitmap iteration for filtered aggregators
URL: https://github.com/apache/incubator-druid/issues/6889#issuecomment-456629007
 
 
   I need to re-evaluate this in the context of #6794.
   
   Solution B yields good improvements with the current one-row-at-a-time query engine,but will likely not work as well with the vectorized query engine, since even low-selectivity filters are likely to have at least one matching row per batch (the default batch size in #6794 is 512 rows).
   
   On the other hand, it becomes possible to implement solution A on a per-batch basis. Right now, it looks like #6794 does not use bitmap iteration to build the list of matching rows yet, but checks the value of each row instead (see `SingleValueStringVectorValueMatcher`), so there might be room for improving filtered aggregator performance there as well. I'm going to try implementing that on top of the `vectoreyes` (what a pun @gianm) branch of #6794 to see how it goes.

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