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From "Ted Yu (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-9272) A simple parallel, unordered scanner
Date Fri, 06 Sep 2013 23:35:52 GMT

    [ https://issues.apache.org/jira/browse/HBASE-9272?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13760749#comment-13760749
] 

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

{code}
+   * close the parallel scanner, callers are strongly encouraged to call this method
+   * doesn't wait until the threapool actually closes
+   */
+  @Override
+  public void close() {
+  }
{code}
Should ExecutorService pool be shut down in the above method ?
{code}
+      } catch (InterruptedException ix) {
+        // ignore
{code}
Please restore interrupt status.

Patch for trunk would be nice.
                
> 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, 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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