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From "Lars Hofhansl (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HBASE-9272) A simple parallel, unordered scanner
Date Tue, 20 Aug 2013 17:40:53 GMT
Lars Hofhansl created HBASE-9272:

             Summary: A simple parallel, unordered scanner
                 Key: HBASE-9272
                 URL: https://issues.apache.org/jira/browse/HBASE-9272
             Project: HBase
          Issue Type: New Feature
            Reporter: Lars Hofhansl
            Priority: Minor

The contract of ClientScanner is to return rows in sort order, that limits the order in which
region can be scanned.
I propose a simple ParallelScanner that does not have this requirement and queries regions
in parallel, return whatever gets returned first.

This is generally useful for scans that filter a lot of data on the server, or in cases where
the client can very quickly react to the returned data.

I have a simple prototype (doesn't error handling right, and might be a bit heavy on the synchronization
side - it used a BlockingQueue to hand data between the client using the scanner and the threads
doing the scanner, it also could potentially starve some scanners long enugh to time out at
the server).
On the plus side, it's only a 130 lines of code. :)

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