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https://issues.apache.org/jira/browse/HIVE-9503?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14296175#comment-14296175
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Chao commented on HIVE-9503:
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In MR, both conditional task AND backup task are used, but for us, only backup
task is needed, since no decision needs to be made (only one mapjoin task). If
we always use backup task for auto converted join, it will add overhead to plan
compilation, because to generate a backup task we need to clone the whole
operator tree.
> Update 'hive.auto.convert.join.noconditionaltask.*' descriptions
> ----------------------------------------------------------------
>
> Key: HIVE-9503
> URL: https://issues.apache.org/jira/browse/HIVE-9503
> Project: Hive
> Issue Type: Bug
> Components: Configuration
> Reporter: Szehon Ho
> Priority: Minor
>
> 'hive.auto.convert.join.noconditionaltask' flag does not apply to Spark or
> Tez, and only to MR (which has the legacy conditional mapjoin)
> However, 'hive.auto.convert.join.noconditionaltask.size' flag does apply to
> Spark, Tez, and MR, even though the description indicates it only applies if
> the above flag is on, which is true only for MR.
> These configs should be updated to reflect this case.
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