[jira] [Created] (HBASE-19047) CP exposed Scanner types should not extend Shipper

["Anoop Sam John (JIRA)" <ji...@apache.org>]

Anoop Sam John created HBASE-19047:
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             Summary: CP exposed Scanner types should not extend Shipper
                 Key: HBASE-19047
                 URL: https://issues.apache.org/jira/browse/HBASE-19047
             Project: HBase
          Issue Type: Sub-task
            Reporter: Anoop Sam John
            Assignee: Anoop Sam John
             Fix For: 2.0.0-alpha-4


Shipper is a IA.Private interface and very much internal.. 
Right now CP exposed RegionScanner is extending this and so exposing the shipped() method. This by mistake is called, can harm the correctness of the cells in the Results.

preScannerOpen() allowing to return a new Scanner is also problematic now.  This can allow users to create a Region scanner from Region and then wrap it and return back (Well same can be done by postScannerOpen also), it can so happen that the wrapper is not implementing the shipped() properly.  In any way exposing the shipped () is problematic.

Solution
1. Remove preScannerOpen() , the use case I can think of is wrapping the original scanner. The original scanner can be created by Region.getScanner way only..  May be no need to remove this hook.  Just remove the ability for it to return a RegionScanner instance.  Call this with the Scan object and the CP can change the Scan object if they want.
2. Let RegionScanner not extending Shipper but only RegionScannerImpl implements this
3. We have ref to the RegionScanner created by core and let that be used by RegionScannerShippedCallBack when the post hook doing a wrap.



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