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From "Neil Ferguson (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-10311) Add Scan object to preScannerNext and postScannerNext methods on RegionObserver
Date Fri, 10 Jan 2014 16:31:51 GMT

    [ https://issues.apache.org/jira/browse/HBASE-10311?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13867960#comment-13867960
] 

Neil Ferguson commented on HBASE-10311:
---------------------------------------

Just made this patch, then realised that I can accomplish what I want by mapping RegionScanner
-> Scan in postScannerOpen, then looking up this map in preScannerNext and postScannerNext.


VisibilityController seems to do something similar already using a weak hashmap. 

This approach seems a little brittle, since there's theoretically no guarantee that the scanner
that is passed to postScannerOpen is the same on that is passed to preScannerNext and postScannerNext.
Perhaps we should change the docs to explicitly specify that this will always be the case.

Anyway, since it doesn't involve changing the coprocessor interface, I'll take this approach.
The patch to modify the coprocessor interface is attached if anyone wants it. Feel free to
close this ticket otherwise.

> Add Scan object to preScannerNext and postScannerNext methods on RegionObserver
> -------------------------------------------------------------------------------
>
>                 Key: HBASE-10311
>                 URL: https://issues.apache.org/jira/browse/HBASE-10311
>             Project: HBase
>          Issue Type: New Feature
>          Components: Coprocessors
>    Affects Versions: 0.96.1.1
>            Reporter: Neil Ferguson
>         Attachments: HBASE-10311.patch
>
>
> I'd like to be able to access the org.apache.hadoop.hbase.client.Scan that was used to
create a scanner in the RegionObserver.preScannerNext and RegionObserver.postScannerNext methods.
> The Scan object is available in the preScannerOpen method, but not in the preScannerNext
or postScannerNext methods.
> The reason is that I'd like to access the attributes of the Scan object. I want to do
some resource management in the coprocessor based on some attributes of the Scan object (like,
who created it).
> Alternatively, does anybody know of another way to get hold of the Scan object in these
methods without modifying things?



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