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https://issues.apache.org/jira/browse/HIVE-20252?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Deepak Jaiswal updated HIVE-20252:
----------------------------------
Status: Patch Available (was: In Progress)
> Semijoin Reduction : Cycles due to semi join branch may remain undetected if
> small table side has a map join upstream.
> ----------------------------------------------------------------------------------------------------------------------
>
> Key: HIVE-20252
> URL: https://issues.apache.org/jira/browse/HIVE-20252
> Project: Hive
> Issue Type: Bug
> Reporter: Deepak Jaiswal
> Assignee: Deepak Jaiswal
> Priority: Major
>
> For eg,
>
> # 2018-07-26T17:22:14,664 DEBUG [51377701-dc98-424f-82e0-bbb5d6c84316 main]
> optimizer.SharedWorkOptimizer: Before SharedWorkOptimizer:
> #
> TS[0]-FIL[96]-SEL[2]-MAPJOIN[156]-MAPJOIN[157]-MAPJOIN[161]-MAPJOIN[162]-FIL[47]-SEL[48]-MAPJOIN[163]-FIL[66]-SEL[67]-TNK[105]-GBY[68]-RS[69]-GBY[70]-SEL[71]-RS[72]-SEL[73]-LIM[74]-FS[75]
> #
> -SEL[142]-GBY[143]-RS[144]-GBY[145]-RS[155]
> # TS[3]-FIL[97]-SEL[5]-RS[34]-MAPJOIN[156]
> # TS[6]-FIL[98]-SEL[8]-RS[37]-MAPJOIN[157]
> # TS[9]-FIL[99]-SEL[11]-MAPJOIN[158]-GBY[40]-RS[42]-MAPJOIN[161]
> # TS[12]-FIL[100]-SEL[14]-RS[16]-MAPJOIN[158]
> # -SEL[131]-GBY[132]-EVENT[133]
> #
> TS[19]-FIL[101]-SEL[21]-MAPJOIN[159]-GBY[29]-RS[30]-GBY[31]-SEL[32]-RS[45]-MAPJOIN[162]
> # TS[22]-FIL[102]-SEL[24]-RS[26]-MAPJOIN[159]
> # -SEL[139]-GBY[140]-EVENT[141]
> #
> TS[49]-FIL[103]-SEL[51]-MAPJOIN[160]-GBY[59]-RS[60]-GBY[61]-SEL[62]-RS[64]-MAPJOIN[163]
> # TS[52]-FIL[104]-SEL[54]-RS[56]-MAPJOIN[160]
> # -SEL[147]-GBY[148]-EVENT[149]
> #
> #
> # DPP information stored in the cache: \{TS[19]=[EVENT[141]],
> TS[9]=[EVENT[133]], TS[49]=[RS[155], EVENT[149]]}
>
> The semi join branch in line 3 feeds into TS[49] in line 12 which feeds to
> MAPJOIN[163] going back to parent of the semi join branch at line 2.
> The logic to detect cycle may fail as there is a MAPJOIN[160] at line 12
> which could cause the logic to look for wrong TS. The logic to find TS
> operator upstream must use findOperatorsUpstream() and examine each TS Op for
> complete coverage.
>
> cc [~jcamachorodriguez]
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