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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (ACCUMULO-3602) BatchScanner optimization for AccumuloInputFormat
Date Thu, 02 Apr 2015 02:52:53 GMT

    [ https://issues.apache.org/jira/browse/ACCUMULO-3602?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14392035#comment-14392035
] 

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_r27629663
  
    --- Diff: core/src/main/java/org/apache/accumulo/core/client/mapreduce/InputFormatBase.java
---
    @@ -323,7 +382,7 @@ protected static TabletLocator getTabletLocator(JobContext context)
throws Table
          * @since 1.6.0
          */
         @Override
    -    protected void setupIterators(TaskAttemptContext context, Scanner scanner, String
tableName, org.apache.accumulo.core.client.mapreduce.RangeInputSplit split) {
    +    protected void setupIterators(TaskAttemptContext context, ScannerBase scanner, String
tableName, org.apache.accumulo.core.client.mapreduce.AccumuloInputSplit split) {
    --- End diff --
    
    Sorry, we can't change these as they'd break API from 1.6.0. We can add to the API for
1.7.0, but we can't remove. Need to deprecate the ones that take Scanner and add in a new
one for ScannerBase. 


> 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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