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Posted to github@arrow.apache.org by GitBox <gi...@apache.org> on 2022/10/15 21:59:28 UTC

[GitHub] [arrow-datafusion] isidentical opened a new pull request, #3848: Handle cardinality estimation for disjoint inner and outer joins

isidentical opened a new pull request, #3848:
URL: https://github.com/apache/arrow-datafusion/pull/3848

   # Which issue does this PR close?
   
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   Closes #3802 .
   
    # Rationale for this change
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    Why are you proposing this change? If this is already explained clearly in the issue then this section is not needed.
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   When we know for a fact that an inner join is disjoint, we can estimate the cardinality of an inner join with (at least) one disjoint column as `0`. From there, we can derive the cardinality of a left/right and full outer joins.
   
   # What changes are included in this PR?
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   There is no need to duplicate the description in the issue here but it is sometimes worth providing a summary of the individual changes in this PR.
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   We now take an `is_exact` flag in `estimate_join_cardinality` which is only `true` when both left and right are originating directly from table providers (which might change in the future if we collect more statistics during materialization points both in DF and Ballista, and somehow adaptively optimize the parent plans according to that). If that `is_exact` flag is true and if we identify a disjoint column when calculating the inner join cardinality, we now infer the cardinality of an inner join as 0. 
   
   Since the cardinality of left/right/full outer joins can be derived from the inner join's cardinality (e.g. a disjoint left outer join would result with the number of rows from the left side), this PR also adds support for inferring their cardinality. 
   
   # Are there any user-facing changes?
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   No.
   
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[GitHub] [arrow-datafusion] alamb merged pull request #3848: Handle cardinality estimation for disjoint inner and outer joins

Posted by GitBox <gi...@apache.org>.
alamb merged PR #3848:
URL: https://github.com/apache/arrow-datafusion/pull/3848


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[GitHub] [arrow-datafusion] alamb commented on pull request #3848: Handle cardinality estimation for disjoint inner and outer joins

Posted by GitBox <gi...@apache.org>.
alamb commented on PR #3848:
URL: https://github.com/apache/arrow-datafusion/pull/3848#issuecomment-1282432548

   Thanks @isidentical 


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