[jira] [Commented] (HBASE-16296) Reverse scan performance degrades when scanner cache size matches page filter size

["James Taylor (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HBASE-16296?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15396750#comment-15396750 ] 

James Taylor commented on HBASE-16296:
--------------------------------------

To setup, follow the directions in generatedata-snippet.java to create and populate the table. Run the repro-snippet.java to demonstrate the issue:
- keep the {{hbase.client.scanner.caching}} at 5 and notice the long pause before "Done" is printed.
- change {{hbase.client.scanner.caching}}  to 7 and notice that there's no longer a pause when the script executes.

Note that functionally, it works, but the performance severely degrades when the {{hbase.client.scanner.caching}} value is equal to the number of rows in the PageFilter.

FYI, [~lhofhansl].

> Reverse scan performance degrades when scanner cache size matches page filter size
> ----------------------------------------------------------------------------------
>
>                 Key: HBASE-16296
>                 URL: https://issues.apache.org/jira/browse/HBASE-16296
>             Project: HBase
>          Issue Type: Bug
>            Reporter: James Taylor
>         Attachments: generatedata-snippet.java, repro-snippet.java
>
>
> When a reverse scan is done, the server seems to not know it's done when the scanner cache size matches the number of rows in a PageFilter. See PHOENIX-3121 for how this manifests itself. We have a standalone, pure HBase API reproducer too that I'll attach (courtesy of [~churromorales] and [~mujtabachohan]).



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