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https://issues.apache.org/jira/browse/HIVE-24016?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17173114#comment-17173114
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Stamatis Zampetakis commented on HIVE-24016:
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Note that I didn't try to test if the transformation described above is applied
by {{SharedWorkOptimizer}} but for sure it is something not covered by
{{SemiJoinReductionMerge}} at the moment.
> Share bloom filter construction branch in multi column semijoin reducers
> ------------------------------------------------------------------------
>
> Key: HIVE-24016
> URL: https://issues.apache.org/jira/browse/HIVE-24016
> Project: Hive
> Issue Type: Improvement
> Reporter: Stamatis Zampetakis
> Assignee: Stamatis Zampetakis
> Priority: Major
>
> In HIVE-21196, we add a transformation capable of merging single column
> semijoin reducers to multi column semijoin reducer.
> Currently it transforms the subplan SB0 to subplan SB1.
> +SB0+
> {noformat}
> / RS -> TS_1[Editor]
> / SEL[fname] - GB - RS - GB - RS -> TS_0[Author]
> SOURCE
> \ SEL[lname] - GB - RS - GB - RS -> TS_0[Author]
> \ RS -> TS_1[Editor]
> TS_0[Author] - FIL[in_bloom(fname) ^ in_bloom(lname)]
> TS_1[Editor] - FIL[in_bloom(fname) ^ in_bloom(lname)]
> {noformat}
> +SB1+
> {noformat}
> / SEL[fname,lname] - GB - RS - GB - RS -> TS[Author] -
> FIL[in_bloom(hash(fname,lname))]
> SOURCE
> \ SEL[fname,lname] - GB - RS - GB - RS -> TS[Editor] -
> FIL[in_bloom(hash(fname,lname))]
> {noformat}
> Observe that in SB1 we could share the common path that creates the bloom
> filter (SEL - GB - RS -GB) to obtain a plan like SB2.
> +SB2+
> {noformat}
> / RS -> TS[Author] -
> FIL[in_bloom(hash(fname,lname))]
> SOURCE - SEL[fname,lname] - GB - RS - GB -
> \ RS -> TS[Editor] -
> FIL[in_bloom(hash(fname,lname))]
> {noformat}
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