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From "Ken Weiner (JIRA)" <j...@apache.org>
Subject [jira] Created: (HBASE-1759) Ability to specify scanner caching on a per-scan basis
Date Tue, 11 Aug 2009 18:10:15 GMT
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

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:
      // Use the caching from the Scan.  If not set, use the default cache setting for this
      if (this.scan.getCaching() > 0) {
        this.caching = this.scan.getCaching();
      } else {
        this.caching = HTable.this.scannerCaching;

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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