[jira] [Commented] (CALCITE-7380) Add support for worst-case optimal join algorithms

["Julian Hyde (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CALCITE-7380?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18052248#comment-18052248 ] 

Julian Hyde commented on CALCITE-7380:
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Sounds interesting. Would this be an in-memory implementation (i.e. enumerable convention)?

How would you represent the plan for this join? Would you have an 'umbrella' relational operator that contains all of the constituent joins?

> Add support for worst-case optimal join algorithms
> --------------------------------------------------
>
>                 Key: CALCITE-7380
>                 URL: https://issues.apache.org/jira/browse/CALCITE-7380
>             Project: Calcite
>          Issue Type: Improvement
>          Components: core
>    Affects Versions: 1.42.0
>            Reporter: TJ Banghart
>            Assignee: TJ Banghart
>            Priority: Major
>         Attachments: p1891-freitag.pdf
>
>
> This issue proposes introducing worst-case optimal join (WCOJ) algorithms into Calcite as an opt-in optimization. WCOJs evaluate multi-way joins in a way that avoids generating large intermediate results and guarantees runtime proportional to the worst-case output size of the query, which can significantly outperform traditional binary join plans for certain query patterns (e.g., cyclic or graph-like joins).
> The implementation would follow a hybrid approach, similar to [Freitag et al. (PVLDB 2020|https://db.in.tum.de/~freitag/papers/p1891-freitag.pdf]), where the optimizer can choose worst-case optimal joins when beneficial but fall back to existing join strategies when they are more appropriate.



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