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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (ACCUMULO-3602) BatchScanner optimization for AccumuloInputFormat
Date Fri, 17 Apr 2015 00:03:37 GMT

    [ https://issues.apache.org/jira/browse/ACCUMULO-3602?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14498998#comment-14498998
] 

ASF GitHub Bot commented on ACCUMULO-3602:
------------------------------------------

Github user keith-turner commented on a diff in the pull request:

    https://github.com/apache/accumulo/pull/25#discussion_r28560936
  
    --- Diff: core/src/main/java/org/apache/accumulo/core/client/mapred/AbstractInputFormat.java
---
    @@ -629,32 +676,37 @@ public float getProgress() throws IOException {
             }
             for (Map.Entry<KeyExtent,List<Range>> extentRanges : tserverBin.getValue().entrySet())
{
               Range ke = extentRanges.getKey().toDataRange();
    -          for (Range r : extentRanges.getValue()) {
    -            if (autoAdjust) {
    -              // divide ranges into smaller ranges, based on the tablets
    -              RangeInputSplit split = new RangeInputSplit(tableName, tableId, ke.clip(r),
new String[] {location});
    -
    -              split.setOffline(tableConfig.isOfflineScan());
    -              split.setIsolatedScan(tableConfig.shouldUseIsolatedScanners());
    -              split.setUsesLocalIterators(tableConfig.shouldUseLocalIterators());
    -              split.setMockInstance(mockInstance);
    -              split.setFetchedColumns(tableConfig.getFetchedColumns());
    -              split.setPrincipal(principal);
    -              split.setToken(token);
    -              split.setInstanceName(instance.getInstanceName());
    -              split.setZooKeepers(instance.getZooKeepers());
    -              split.setAuths(auths);
    -              split.setIterators(tableConfig.getIterators());
    -              split.setLogLevel(logLevel);
    -
    -              splits.add(split);
    -            } else {
    -              // don't divide ranges
    -              ArrayList<String> locations = splitsToAdd.get(r);
    -              if (locations == null)
    -                locations = new ArrayList<String>(1);
    -              locations.add(location);
    -              splitsToAdd.put(r, locations);
    +          if (batchScan) {
    +            // group ranges by tablet to be read by a BatchScanner
    +            ArrayList<Range> clippedRanges = new ArrayList<Range>();
    +            for(Range r: extentRanges.getValue())
    --- End diff --
    
    Should anything need to be added the `setBatchScan(...)` javadoc regarding `autoAdjust`?


> 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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