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Date: Sat, 5 Oct 2013 00:18:42 +0000 (UTC)
From: "Ted Yu (JIRA)" <jira@apache.org>
To: issues@hbase.apache.org
Message-ID: <JIRA.12664651.1377020437270.18185.1380932322939@arcas>
In-Reply-To: <JIRA.12664651.1377020437270@arcas>
References: <JIRA.12664651.1377020437270@arcas>
Subject: [jira] [Commented] (HBASE-9272) A simple parallel, unordered
 scanner
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    [ https://issues.apache.org/jira/browse/HBASE-9272?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13786783#comment-13786783 ] 

Ted Yu commented on HBASE-9272:
-------------------------------

License is missing for ParallelClientScanner.java
Please add annotation for audience.
{code}
+  // reader interface
+  public static interface ResultReader {
...
+  // writer interface
+  public static interface ResultWriter {
{code}
Looks like the above classes can be private.
{code}
+      } catch (InterruptedException ix) {
+        // ignore
{code}
Restore interrupt status ?

> 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
>            Assignee: Lars Hofhansl
>            Priority: Minor
>         Attachments: 9272-0.94.txt, 9272-0.94-v2.txt, 9272-0.94-v3.txt, 9272-0.94-v4.txt, 9272-trunk.txt, ParallelClientScanner.java, ParallelClientScanner.java
>
>
> 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 do 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 scanning, 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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