[jira] [Updated] (HIVE-9007) Hive may generate wrong plan for map join queries due to IdentityProjectRemover [Spark Branch]

["Szehon Ho (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/HIVE-9007?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Szehon Ho updated HIVE-9007:
----------------------------
    Attachment: HIVE-9007-spark.patch

IdentityProjectRemover removes unnecessary Select/Fil operators.

I tried some hacks on Spark compiler's mapjoin optimizers to work with this kind of graph (where multiple RS are connected to each other without intermediate Sel/Fil).  But it's too hard as this affects where they cut the ReduceWork, and loses the rowSchema from for ReduceSink -> HTSink conversion.  So disabling for spark compilation.

Wrote a new test that stresses this case.  Interestingly, it does not seem to work for MapReduce either.

> Hive may generate wrong plan for map join queries due to IdentityProjectRemover [Spark Branch]
> ----------------------------------------------------------------------------------------------
>
>                 Key: HIVE-9007
>                 URL: https://issues.apache.org/jira/browse/HIVE-9007
>             Project: Hive
>          Issue Type: Sub-task
>          Components: Spark
>    Affects Versions: spark-branch
>            Reporter: Chao
>            Assignee: Szehon Ho
>         Attachments: HIVE-9007-spark.patch
>
>
> HIVE-8435 introduces a new logical optimizer called IdentityProjectRemover, which may cause map join in spark branch to generate wrong plan.
> Currently, the map join conversion in spark branch first goes through a method {{convertJoinMapJoin}}, which replaces a join op with a mapjoin op, removes RS associated with big table, and keep RSs for all small tables. Afterwards, in {{SparkReduceSinkMapJoinProc}} it replaces all parent RSs of the mapjoin op with HTS (note it doesn't check whether the RS belongs to small table or big table.)
> The issue arises, when IdentityProjectRemover comes into play, which may result into a situation that a operator tree has two consecutive RSs. Imaging the following example:
> {noformat}
>           Join               MapJoin
>           / \                /   \
>         RS   RS   --->     RS     RS
>        /      \           /         \
>       TS       RS       TS          TS (big table)
>                 \      (small table)
>                  TS
> {noformat}
> In this case, all parents of the mapjoin op will be RS, even the branch for big table! In {{SparkReduceSinkMapJoinProc}}, they will be replaced with HTS, which is obviously incorrect.



--
This message was sent by Atlassian JIRA
(v6.3.4#6332)