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From "Himanshu Vashishtha (JIRA)" <j...@apache.org>
Subject [jira] Updated: (HBASE-3607) Cursor functionality for results generated by Coprocessors
Date Mon, 07 Mar 2011 08:41:59 GMT

     [ https://issues.apache.org/jira/browse/HBASE-3607?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel

Himanshu Vashishtha updated HBASE-3607:

    Attachment: patch-2.txt

poc patch for the cursor-cp-server support

> Cursor functionality for results generated by Coprocessors
> ----------------------------------------------------------
>                 Key: HBASE-3607
>                 URL: https://issues.apache.org/jira/browse/HBASE-3607
>             Project: HBase
>          Issue Type: New Feature
>          Components: coprocessors
>            Reporter: Himanshu Vashishtha
>         Attachments: patch-2.txt
> I tried to come up with a scanner like functionality for results generated by coprocessors
at region level. 
> This is just a poc, and it will be good to have your comments on it.
> It has support for both Incremental and In-memory Result sets. Attached is a patch that
has a test case for an incremental result (i.e., client receives a cursorId from the CP core
method, it instantiates a cursor object and iterates over the result set. He can set a cache
limit on the CursorCallable object to reduce the number of rpc --> just like scanners.
> In its current state, it has some limitations too :)), like, it is region specific only,
i.e., one can instantiate and use cursor at one region only (and that region is determined
by the input row while instantiating the cursor). I will try to expand it so that it can have
atleast a sequential access to other regions, but as I said, I want the opinion of experts
to know whether this approach really makes some sense or not.
> I have tested it with the inbuilt testing framework on my laptop only.
> It will be good if I copy the use case here in the description too:
> Test table has rows like:
>  /**
>    * The scenario is that I have these rows keys in the test table:
>   'aaa-123'
>   'aaa-456'
>   'abc-111'
>   'abd-111'
>   'abd-222'
>   & I want to return:
>   ('aaa', 2)
>   ('abc', 1)
>   ('abd', 2)

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