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From "ASF GitHub Bot (JIRA)" <>
Subject [jira] [Commented] (ACCUMULO-3602) BatchScanner optimization for AccumuloInputFormat
Date Fri, 17 Apr 2015 15:04:00 GMT


ASF GitHub Bot commented on ACCUMULO-3602:

Github user joshelser commented on a diff in the pull request:
    --- Diff: core/src/main/java/org/apache/accumulo/core/client/mapreduce/
    @@ -325,27 +362,12 @@ protected void setupIterators(TaskAttemptContext context, Scanner
scanner, Strin
          *          the Hadoop context for the configured job
          * @param scanner
          *          the scanner to configure
    +     * @deprecated since 1.7.0; Use {@link #contextIterators} instead.
         protected void setupIterators(TaskAttemptContext context, Scanner scanner) {
    -      setupIterators(context, scanner, null);
    -    }
    -    /**
    -     * Initialize a scanner over the given input split using this task attempt configuration.
    -     */
    -    protected void setupIterators(TaskAttemptContext context, Scanner scanner, org.apache.accumulo.core.client.mapreduce.RangeInputSplit
split) {
    --- End diff --
    Those are different methods. Note that the one you linked includes a `String tableName`
argument where the removed one does not. I think we need both methods.

> BatchScanner optimization for AccumuloInputFormat
> -------------------------------------------------
>                 Key: ACCUMULO-3602
>                 URL:
>             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
> 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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