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From "Jonathan Gray (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HBASE-1759) Ability to specify scanner caching on a per-scan basis
Date Wed, 12 Aug 2009 21:13:14 GMT

    [ https://issues.apache.org/jira/browse/HBASE-1759?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12742575#action_12742575

Jonathan Gray commented on HBASE-1759:

+1 Patch looks good.  Any other committers want to weigh in before commit?

> Ability to specify scanner caching on a per-scan basis
> ------------------------------------------------------
>                 Key: HBASE-1759
>                 URL: https://issues.apache.org/jira/browse/HBASE-1759
>             Project: Hadoop HBase
>          Issue Type: Improvement
>          Components: client
>    Affects Versions: 0.20.0
>            Reporter: Ken Weiner
>         Attachments: HBASE-1759-v2.patch, HBASE-1759.patch
> I think that clients should have the ability to configure the scanner caching setting
on a per-scan basis via the org.apache.hadoop.hbase.client.Scan object.  I propose adding
a new caching property to the Scan class which would override the HTable.scannerCaching property
if set.  This would turn the HTable.scannerCaching property into more of a default setting.
> The code inside ClientScanner (an inner-class implementation of ResultScanner) would
look like this:
> {code}
>       // Use the caching from the Scan.  If not set, use the default cache setting for
this table.
>       if (this.scan.getCaching() > 0) {
>         this.caching = this.scan.getCaching();
>       } else {
>         this.caching = HTable.this.scannerCaching;
>       }
> {code}
> Note that currently the only option for per-scan scanner caching configuration is to
modify the state of HTable for each Scan.  This could lead to confusion when HTables are pooled
since the pool would potentially end up with many HTables all configured differently.
> I will attach a patch.  I'm looking forward to hearing your comments.

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