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From "Rui Li (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HIVE-16600) Refactor SetSparkReducerParallelism#needSetParallelism to enable parallel order by in multi_insert cases
Date Wed, 17 May 2017 04:06:04 GMT

    [ https://issues.apache.org/jira/browse/HIVE-16600?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16013480#comment-16013480
] 

Rui Li commented on HIVE-16600:
-------------------------------

Hi [~xuefuz], I'd like to confirm what the standard says about this case. For a query {{from
(select k from src order by k) A insert overwrite table target select A.k limit 5}}. Does
the data in target has to be ordered or top 5 from A? Could you share your thoughts? Thanks.

> 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, 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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