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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 02:16:54 GMT

    [ https://issues.apache.org/jira/browse/ACCUMULO-3602?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14391988#comment-14391988
] 

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_r27628588
  
    --- Diff: core/src/main/java/org/apache/accumulo/core/client/mapred/AbstractInputFormat.java
---
    @@ -458,53 +512,27 @@ public void initialize(InputSplit inSplit, JobConf job) throws IOException
{
             columns = tableConfig.getFetchedColumns();
           }
     
    -      try {
    -        log.debug("Creating connector with user: " + principal);
    -        log.debug("Creating scanner for table: " + table);
    -        log.debug("Authorizations are: " + authorizations);
    -        if (isOffline) {
    -          scanner = new OfflineScanner(instance, new Credentials(principal, token), split.getTableId(),
authorizations);
    -        } else if (instance instanceof MockInstance) {
    -          scanner = instance.getConnector(principal, token).createScanner(split.getTableName(),
authorizations);
    -        } else {
    -          ClientConfiguration clientConf = getClientConfiguration(job);
    -          ClientContext context = new ClientContext(instance, new Credentials(principal,
token), clientConf);
    -          scanner = new ScannerImpl(context, split.getTableId(), authorizations);
    -        }
    -        if (isIsolated) {
    -          log.info("Creating isolated scanner");
    -          scanner = new IsolatedScanner(scanner);
    -        }
    -        if (usesLocalIterators) {
    -          log.info("Using local iterators");
    -          scanner = new ClientSideIteratorScanner(scanner);
    -        }
    -        setupIterators(job, scanner, split.getTableName(), split);
    -      } catch (Exception e) {
    -        throw new IOException(e);
    -      }
    -
           // setup a scanner within the bounds of this split
    -      for (Pair<Text,Text> c : columns) {
    +      for (Pair<Text, Text> c : columns) {
    --- End diff --
    
    Extra unnecessary space.


> 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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