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https://issues.apache.org/jira/browse/HBASE-1996?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Erik Rozendaal updated HBASE-1996:
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Attachment: 1996-0.20.3-v3.patch
The 1996-0.20.3-v3.patch sets the default limit to "unlimited", so 0.20.3
should have the same scanning behavior as 0.20.2 unless the configuration
parameter is set explicitly.
PS The fix-version of this issue is 0.21 and is marked as incompatible change.
Maybe the 0.20.3 patch should be moved to a new issue or this issue changed?
> 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-v3.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.
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