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https://issues.apache.org/jira/browse/HBASE-7952?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13589141#comment-13589141
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stack commented on HBASE-7952:
------------------------------

[~colorant] Thank you for digging in this part of the code.

bq. And no one will call checkColumn for different HFiles with update() in 
between files to re-walk through the target columns. 

We will not need to readjust/notice as we cross file boundaries?  It seems like 
this facility is unused now but you foresee no need in the future?  I can well 
imagine that this was added as a 'just-in-case' in the past and that reality 
turned out to be otherwise.

Are there unit tests that verify your assertions that:

bq.  All columns will be feed to checkColumn() in order.

... even as we cross file boundaries?

Otherwise, it looks like a nice optimization if it passes.  Thanks.





[~lhofhansl] You want to take a look see?

                
> Remove update() and Improve ExplicitColumnTracker performance.
> --------------------------------------------------------------
>
>                 Key: HBASE-7952
>                 URL: https://issues.apache.org/jira/browse/HBASE-7952
>             Project: HBase
>          Issue Type: Improvement
>          Components: regionserver
>    Affects Versions: 0.94.1, 0.94.5
>            Reporter: Raymond Liu
>            Assignee: Raymond Liu
>             Fix For: 0.96.0
>
>         Attachments: HBASE_7952.patch
>
>
> In ColumnTracker.java, the update() method is not used by anyone now. And no 
> one will call checkColumn for different HFiles with update() in between files 
> to re-walk through the target columns. All columns will be feed to 
> checkColumn() in order.
> So, within ExplicitColumnTracker, the target columns can be optimized to not 
> dynamic maintain a changing list of columns yet to match. Instead, just move 
> index through it is enough.
> with this optimization to save the time for avoid reconstruct a columns array 
> upon each row, the checkColumn method's performance could be improved by 
> 10-20%.

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