[jira] Commented: (HBASE-1996) Configure scanner buffer in bytes instead of number of rows

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

    [ https://issues.apache.org/jira/browse/HBASE-1996?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12796054#action_12796054 ] 

stack commented on HBASE-1996:
------------------------------

Erik: Thanks for making the size configurable.  Thanks for explaining why client needs to match server.

Can you make it so that unless an explicit size has been set, the behavior is that things work as they do now?  So that this sizing of data only cuts in if you set an explicit value in hbase.client.scanner.max.result.size?  So the behavior is as it is now, pre-patch, unless you change hbase.client.scanner.max.result.size from its default of -1?

Once committed, we should file the issue you suggest for 0.21 where we do better communication of state between client and server during scans.

> Configure scanner buffer in bytes instead of number of rows
> -----------------------------------------------------------
>
>                 Key: HBASE-1996
>                 URL: https://issues.apache.org/jira/browse/HBASE-1996
>             Project: Hadoop HBase
>          Issue Type: Improvement
>            Reporter: Dave Latham
>            Assignee: Dave Latham
>             Fix For: 0.21.0
>
>         Attachments: 1966.patch, 1996-0.20.3-v2.patch, 1996-0.20.3.patch
>
>
> Currently, the default scanner fetches a single row at a time.  This makes for very slow scans on tables where the rows are not large.  You can change the setting for an HTable instance or for each Scan.
> It would be better to have a default that performs reasonably well so that people stop running into slow scans because they are evaluating HBase, aren't familiar with the setting, or simply forgot.  Unfortunately, if we increase the value of the current setting, then we run the risk of running OOM for tables with large rows.  Let's change the setting so that it works with a size in bytes, rather than in rows.  This will allow us to set a reasonable default so that tables with small rows will scan performantly and tables with large rows will not run OOM.
> Note that the case is very similar to table writes as well.  When disabling auto flush, we buffer a list of Put's to commit at once.  That buffer is measured in bytes, so that a small number of large Puts or a lot of small Puts can each fit in a single flush.  If that buffer were measured in number of Put's it would have the same problem that we have for the scan buffer, and we wouldn't be able to set a good default value for tables with different size rows.  Changing the scan buffer to be configured like the write buffer will make it more consistent.

-- 
This message is automatically generated by JIRA.
-
You can reply to this email to add a comment to the issue online.