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From "Ashutosh Chauhan (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HIVE-4318) OperatorHooks hit performance even when not used
Date Tue, 09 Apr 2013 20:58:16 GMT

    [ https://issues.apache.org/jira/browse/HIVE-4318?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13627096#comment-13627096
] 

Ashutosh Chauhan commented on HIVE-4318:
----------------------------------------

I agree with Gunther's analysis and suggestion to remove them altogether. If only reason to
introduce operator level hook was to measure performance that we have failed in that objective
by actually making system slower not faster. Profiling should be done using jvm toolkits like
yourkit, jvisualvm etc., not by modifying code.
                
> OperatorHooks hit performance even when not used
> ------------------------------------------------
>
>                 Key: HIVE-4318
>                 URL: https://issues.apache.org/jira/browse/HIVE-4318
>             Project: Hive
>          Issue Type: Bug
>          Components: Query Processor
>         Environment: Ubuntu LXC (64 bit)
>            Reporter: Gopal V
>            Assignee: Gunther Hagleitner
>
> Operator Hooks inserted into Operator.java cause a performance hit even when it is not
being used.
> For a count(1) query tested with & without the operator hook calls.
> {code:title=with}
> 2013-04-09 07:33:58,920 Stage-1 map = 100%,  reduce = 100%, Cumulative CPU 84.07 sec
> Total MapReduce CPU Time Spent: 1 minutes 24 seconds 70 msec
> OK
> 28800991
> Time taken: 40.407 seconds, Fetched: 1 row(s)
> {code}
> {code:title=without}
> 2013-04-09 07:33:02,355 Stage-1 map = 100%,  reduce = 100%, Cumulative CPU 68.48 sec
> ...
> Total MapReduce CPU Time Spent: 1 minutes 8 seconds 480 msec
> OK
> 28800991
> Time taken: 35.907 seconds, Fetched: 1 row(s)
> {code}
> The effect is multiplied by the number of operators in the pipeline that has to forward
the row - the more operators there are the, the slower the query.
> The modification made to test this was 
> {code:title=Operator.java}
> --- ql/src/java/org/apache/hadoop/hive/ql/exec/Operator.java
> +++ ql/src/java/org/apache/hadoop/hive/ql/exec/Operator.java
> @@ -526,16 +526,16 @@ public void process(Object row, int tag) throws HiveException {
>        return;
>      }
>      OperatorHookContext opHookContext = new OperatorHookContext(this, row, tag);
> -    preProcessCounter();
> -    enterOperatorHooks(opHookContext);
> +    //preProcessCounter();
> +    //enterOperatorHooks(opHookContext);
>      processOp(row, tag);
> -    exitOperatorHooks(opHookContext);
> -    postProcessCounter();
> +    //exitOperatorHooks(opHookContext);
> +    //postProcessCounter();
>    }
> {code}

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