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https://issues.apache.org/jira/browse/HIVE-4318?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13629241#comment-13629241
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Pamela Vagata commented on HIVE-4318:
-------------------------------------
The operator level hooks were introduced to allow a user to profile their query
and see which operator was taking the most time in order to determine whether
or not there are query improvements to be made, not for measuring the
performance of the overall system.
> 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
> Attachments: HIVE-4318.1.patch
>
>
> 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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