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https://issues.apache.org/jira/browse/ACCUMULO-3602?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14376644#comment-14376644
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Eugene Cheipesh commented on ACCUMULO-3602:
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https://github.com/echeipesh/accumulo/tree/ACCUMULO-3602
This moves up the logic to branch on split type all the way to
AbstractRecordReader. This avoids a silly amount of code duplication of
actually creating a second type of reader.
I've tested this code from a client program and it behaves as expected, but I
could use some suggestions on the best way to drive the test from accumulo code
base.
> 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
>
> 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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