[jira] [Created] (IMPALA-10112) Consider skipping FpRateTooHigh() check for bloom filters

["Tim Armstrong (Jira)" <ji...@apache.org>]

Tim Armstrong created IMPALA-10112:
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             Summary: Consider skipping FpRateTooHigh() check for bloom filters
                 Key: IMPALA-10112
                 URL: https://issues.apache.org/jira/browse/IMPALA-10112
             Project: IMPALA
          Issue Type: Improvement
          Components: Backend
            Reporter: Tim Armstrong
            Assignee: Tim Armstrong


This check disables bloom filters on the sender side.

It is inaccurate in cases where there are duplicate values of the filter key on the build side. E.g. many-to-many join or a join with multiple keys. This could be fixed with some effort, but is probably not worth it, because:
* Partition filters are probably still worth evaluating even if there are false positives, because it's cheap and eliminating a partition is still beneficial.
* Runtime filters are dynamically disabled on the scan side if they are ineffective.
* The disabling is fairly unlikely to kick in for partitioned joins because it's only applied to a small subset of the filter, before the Or() operation.

So it's potentially harmful and only likely beneficial for broadcast join filters, in which case it saves a small amount of scan CPU and, for global filters, coordinator RPCs and broadcasting. It's unclear that the complexity is worth it for this relatively small and uncertain benefit.





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