[jira] [Commented] (HBASE-7180) RegionScannerImpl.next() is inefficient.

["Lars Hofhansl (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HBASE-7180?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13508476#comment-13508476 ] 

Lars Hofhansl commented on HBASE-7180:
--------------------------------------

How about another approach:
# introduce a RawRegionScanner interface, which extends RegionScanner.
# RawRegionScanner has all the additional methods on it we need.
# Add a getRawScannner to the RegionScanner interface.
# RegionScannerImpl would then implement RawRegionScanner.

To the coprocessor framework we'd still hand a RegionScanner, but now the coprocessor can get the raw scanner via getRawScanner(). The RegionScannerImpl's implementation of getRawScanner() just returns "this".
Is that better? Or does anybody have another a cleaner idea?

closeRegionOperation and startRegionOperation would still need to be public, so that coprocessors can start/stop region operations.

                
> RegionScannerImpl.next() is inefficient.
> ----------------------------------------
>
>                 Key: HBASE-7180
>                 URL: https://issues.apache.org/jira/browse/HBASE-7180
>             Project: HBase
>          Issue Type: Bug
>            Reporter: Lars Hofhansl
>         Attachments: 7180-0.94-SKETCH.txt, 7180-0.94-v1.txt
>
>
> We just came across a special scenario.
> For our Phoenix project (SQL runtime for HBase), we push a lot of work into HBase via coprocessors. One method is to wrap RegionScanner in coprocessor hooks and then do processing in the hook to avoid returning a lot of data to the client unnecessarily.
> In this specific case this is pretty bad. Since the wrapped RegionScanner's next() does not "know" that it is called this way is still does all of this on each invocation:
> # Starts a RegionOperation
> # Increments the request count
> # set the current read point on a thread local (because generally each call could come from a different thread)
> # Finally does the next on its StoreScanner(s)
> # Ends the RegionOperation
> When this is done in a tight loop millions of times (as is the case for us) it starts to become significant.
> Not sure what to do about this, really. Opening this issue for discussion.
> One way is to extend the RegionScanner with an "internal" next() method of sorts, so that all this overhead can be avoided. The coprocessor could call the regular next() methods once and then just call the cheaper internal version.
> Are there better/cleaner ways?

--
This message is automatically generated by JIRA.
If you think it was sent incorrectly, please contact your JIRA administrators
For more information on JIRA, see: http://www.atlassian.com/software/jira