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From "Eugene Cheipesh (JIRA)" <j...@apache.org>
Subject [jira] [Created] (ACCUMULO-3602) BatchScanner optimization for AccumuloInputFormat
Date Wed, 18 Feb 2015 21:52:12 GMT
Eugene Cheipesh created ACCUMULO-3602:
-----------------------------------------

             Summary: 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


Curently `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`.  `InputFormatBase`,
extended by `AccumuloInputFormat`, would then be able to inspect the type of the split in
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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