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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 02:55:53 GMT

    [ https://issues.apache.org/jira/browse/ACCUMULO-3602?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14392041#comment-14392041
] 

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_r27629755
  
    --- Diff: core/src/main/java/org/apache/accumulo/core/client/mapreduce/RangeInputSplit.java
---
    @@ -135,38 +72,15 @@ public float getProgress(Key currentKey) {
        */
       @Override
       public long getLength() throws IOException {
    -    Text startRow = range.isInfiniteStartKey() ? new Text(new byte[] {Byte.MIN_VALUE})
: range.getStartKey().getRow();
    -    Text stopRow = range.isInfiniteStopKey() ? new Text(new byte[] {Byte.MAX_VALUE})
: range.getEndKey().getRow();
    -    int maxCommon = Math.min(7, Math.min(startRow.getLength(), stopRow.getLength()));
    -    long diff = 0;
    -
    -    byte[] start = startRow.getBytes();
    -    byte[] stop = stopRow.getBytes();
    -    for (int i = 0; i < maxCommon; ++i) {
    -      diff |= 0xff & (start[i] ^ stop[i]);
    -      diff <<= Byte.SIZE;
    -    }
    -
    -    if (startRow.getLength() != stopRow.getLength())
    -      diff |= 0xff;
    -
    -    return diff + 1;
    +    return getRangeLength(range);
       }
     
    -  @Override
    -  public String[] getLocations() throws IOException {
    -    return Arrays.copyOf(locations, locations.length);
    -  }
     
       @Override
       public void readFields(DataInput in) throws IOException {
    --- End diff --
    
    Need to get offline from the serialization.


> 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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