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Posted to issues@calcite.apache.org by "Zhong Yu (JIRA)" <ji...@apache.org> on 2018/03/04 18:45:00 UTC

[jira] [Created] (CALCITE-2202) Aggregate Join Push-down on a Single Side

Zhong Yu created CALCITE-2202:
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             Summary: Aggregate Join Push-down on a Single Side
                 Key: CALCITE-2202
                 URL: https://issues.apache.org/jira/browse/CALCITE-2202
             Project: Calcite
          Issue Type: Improvement
          Components: core
    Affects Versions: next
            Reporter: Zhong Yu
            Assignee: Julian Hyde
             Fix For: next


While investigating https://issues.apache.org/jira/browse/CALCITE-2195, it's apparent that aggregation can be pushed on on a single side (either side), and leave the other side non-aggregated, regardless of whether grouping columns are unique on the other side. My analysis – [http://zhong-j-yu.github.io/aggregate-join-push-down.pdf] .

This may be useful when the metadata is insufficient; in any case, we may try to provide all 3 possible transformations (aggregate on left only; right only; both sides) to the cost based optimizer, so that the cheapest one can be chosen based on stats. 

Does this make any sense, anybody? If it sounds good, I'll implement it and offer a PR. 



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