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Date: Wed, 8 Apr 2015 21:46:12 +0000 (UTC)
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Subject: [jira] [Commented] (ACCUMULO-3602) BatchScanner optimization for
 AccumuloInputFormat
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    [ https://issues.apache.org/jira/browse/ACCUMULO-3602?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14486127#comment-14486127 ] 

ASF GitHub Bot commented on ACCUMULO-3602:
------------------------------------------

Github user joshelser commented on a diff in the pull request:

    https://github.com/apache/accumulo/pull/25#discussion_r28016992
  
    --- Diff: core/src/main/java/org/apache/accumulo/core/client/mapred/AbstractInputFormat.java ---
    @@ -384,7 +387,21 @@ public static InputTableConfig getInputTableConfig(JobConf job, String tableName
       protected abstract static class AbstractRecordReader<K,V> implements RecordReader<K,V> {
         protected long numKeysRead;
         protected Iterator<Map.Entry<Key,Value>> scannerIterator;
    -    protected RangeInputSplit split;
    +    protected org.apache.accumulo.core.client.mapreduce.impl.AccumuloInputSplit split;
    +    protected ScannerBase scannerBase;
    +
    +    /**
    +     * Configures the iterators on a scanner for the given table name.
    +     *
    +     * @param job
    +     *          the Hadoop job configuration
    +     * @param scanner
    +     *          the scanner for which to configure the iterators
    +     * @param tableName
    +     *          the table name for which the scanner is configured
    +     * @since 1.7.0
    +     */
    +    protected abstract void setupIterators(JobConf job, ScannerBase scanner, String tableName, AccumuloInputSplit split);
    --- End diff --
    
    > Looking at code right now the only part that diverges is pulling out default split if they're somehow unavailable in the split. This narrows the interface, hopefully in an acceptable way?
    
    @echeipesh I think your approach looks good.


> BatchScanner optimization for AccumuloInputFormat
> -------------------------------------------------
>
>                 Key: ACCUMULO-3602
>                 URL: https://issues.apache.org/jira/browse/ACCUMULO-3602
>             Project: Accumulo
>          Issue Type: Improvement
>          Components: client
>    Affects Versions: 1.6.1, 1.6.2
>            Reporter: Eugene Cheipesh
>            Assignee: Eugene Cheipesh
>              Labels: performance
>             Fix For: 1.7.0
>
>
> Currently {{AccumuloInputFormat}} produces a split for reach {{Range}} specified in the configuration. Some table indexing schemes, for instance z-order geospacial index, produce large number of small ranges resulting in large number of splits. This is specifically a concern when using {{AccumuloInputFormat}} as a source for Spark RDD where each Split is mapped to an RDD partition.
> Large number of small RDD partitions leads to poor parallism on read and high overhead on processing. A desirable alternative is to group ranges by tablet into a single split and use {{BatchScanner}} to produce the records. Grouping by tablets is useful because it represents Accumulos attempt to distributed stored records and can be influance by the user through table splits.
> The grouping functionality already exists in the internal {{TabletLocator}} class. 
> Current proposal is to modify {{AbstractInputFormat}} such that it generates either {{RangeInputSplit}} or {{MultiRangeInputSplit}} based on a new setting in {{InputConfigurator}}.  {{AccumuloInputFormat}} would then be able to inspect the type of the split and instantiate an appropriate reader.
> The functinality of {{TabletLocator}} should be exposed as a public API in 1.7 as it is useful for optimizations.


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