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https://issues.apache.org/jira/browse/HIVE-3784?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13547768#comment-13547768
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Ashutosh Chauhan commented on HIVE-3784:
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Namit,
I very much like this work, since diffs are all red, which is good since it is
removing lot of unnecessary complexity from the codebase, but Vinod's point is
worth considering. I also see this you have moved mapjoin_subquery.q,
mapjoin_mapjoin.q and such test cases from positive to negative. Do you have a
proposal on what could be done to preserve that optimization of pipelining
multiple map-join operators (even on different keys) in a single mapper?
> de-emphasize mapjoin hint
> -------------------------
>
> Key: HIVE-3784
> URL: https://issues.apache.org/jira/browse/HIVE-3784
> Project: Hive
> Issue Type: Improvement
> Components: Query Processor
> Reporter: Namit Jain
> Assignee: Namit Jain
> Attachments: hive.3784.1.patch, hive.3784.2.patch, hive.3784.3.patch,
> hive.3784.4.patch, hive.3784.5.patch
>
>
> hive.auto.convert.join has been around for a long time, and is pretty stable.
> When mapjoin hint was created, the above parameter did not exist.
> The only reason for the user to specify a mapjoin currently is if they want
> it to be converted to a bucketed-mapjoin or a sort-merge bucketed mapjoin.
> Eventually, that should also go away, but that may take some time to
> stabilize.
> There are many rules in SemanticAnalyzer to handle the following trees:
> ReduceSink -> MapJoin
> Union -> MapJoin
> MapJoin -> MapJoin
> This should not be supported anymore. In any of the above scenarios, the
> user can get the mapjoin behavior by setting hive.auto.convert.join to true
> and not specifying the hint. This will simplify the code a lot.
> What does everyone think ?
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