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From "Xuefu Zhang (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HIVE-16600) Refactor SetSparkReducerParallelism#needSetParallelism to enable parallel order by in multi_insert cases
Date Tue, 23 May 2017 18:43:04 GMT

    [ https://issues.apache.org/jira/browse/HIVE-16600?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16021627#comment-16021627
] 

Xuefu Zhang commented on HIVE-16600:
------------------------------------

Yeah, I agree with [~lirui] that multi-insert operator tree doesn't necessarily branch at
SEL operator. It does if the selected columns in all insert branch are purely projections
and require no shuffles. Nevertheless, it's safer not to make such an assumption.

> Refactor SetSparkReducerParallelism#needSetParallelism to enable parallel order by in
multi_insert cases
> --------------------------------------------------------------------------------------------------------
>
>                 Key: HIVE-16600
>                 URL: https://issues.apache.org/jira/browse/HIVE-16600
>             Project: Hive
>          Issue Type: Sub-task
>            Reporter: liyunzhang_intel
>            Assignee: liyunzhang_intel
>         Attachments: HIVE-16600.1.patch, HIVE-16600.2.patch, HIVE-16600.3.patch, HIVE-16600.4.patch,
HIVE-16600.5.patch, HIVE-16600.6.patch, HIVE-16600.7.patch, mr.explain, mr.explain.log.HIVE-16600
>
>
> multi_insert_gby.case.q
> {code}
> set hive.exec.reducers.bytes.per.reducer=256;
> set hive.optimize.sampling.orderby=true;
> drop table if exists e1;
> drop table if exists e2;
> create table e1 (key string, value string);
> create table e2 (key string);
> FROM (select key, cast(key as double) as keyD, value from src order by key) a
> INSERT OVERWRITE TABLE e1
>     SELECT key, value
> INSERT OVERWRITE TABLE e2
>     SELECT key;
> select * from e1;
> select * from e2;
> {code} 
> the parallelism of Sort is 1 even we enable parallel order by("hive.optimize.sampling.orderby"
is set as "true").  This is not reasonable because the parallelism  should be calcuated by
 [Utilities.estimateReducers|https://github.com/apache/hive/blob/master/ql/src/java/org/apache/hadoop/hive/ql/optimizer/spark/SetSparkReducerParallelism.java#L170]
> this is because SetSparkReducerParallelism#needSetParallelism returns false when [children
size of RS|https://github.com/apache/hive/blob/master/ql/src/java/org/apache/hadoop/hive/ql/optimizer/spark/SetSparkReducerParallelism.java#L207]
is greater than 1.
> in this case, the children size of {{RS[2]}} is two.
> the logical plan of the case
> {code}
>    TS[0]-SEL[1]-RS[2]-SEL[3]-SEL[4]-FS[5]
>                             -SEL[6]-FS[7]
> {code}



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