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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 02:50:53 GMT

    [ https://issues.apache.org/jira/browse/ACCUMULO-3602?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14392032#comment-14392032
] 

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_r27629581
  
    --- Diff: core/src/main/java/org/apache/accumulo/core/client/mapreduce/BatchInputSplit.java
---
    @@ -0,0 +1,151 @@
    +/*
    + * Licensed to the Apache Software Foundation (ASF) under one or more
    + * contributor license agreements.  See the NOTICE file distributed with
    + * this work for additional information regarding copyright ownership.
    + * The ASF licenses this file to You under the Apache License, Version 2.0
    + * (the "License"); you may not use this file except in compliance with
    + * the License.  You may obtain a copy of the License at
    + *
    + *     http://www.apache.org/licenses/LICENSE-2.0
    + *
    + * Unless required by applicable law or agreed to in writing, software
    + * distributed under the License is distributed on an "AS IS" BASIS,
    + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    + * See the License for the specific language governing permissions and
    + * limitations under the License.
    + */
    +package org.apache.accumulo.core.client.mapreduce;
    +
    +import java.io.DataInput;
    +import java.io.DataOutput;
    +import java.io.IOException;
    +import java.util.ArrayList;
    +import java.util.Arrays;
    +import java.util.Collection;
    +import java.util.Collections;
    +
    +import org.apache.accumulo.core.data.Key;
    +import org.apache.accumulo.core.data.PartialKey;
    +import org.apache.accumulo.core.data.Range;
    +
    +/**
    + * The Class BatchInputSplit. Encapsulates a set of Accumulo ranges on a single tablet
for use in Map Reduce jobs.
    + * Can contain several Ranges per split.
    + */
    +public class BatchInputSplit extends AccumuloInputSplit {
    +  private Collection<Range> ranges;
    +  private int scanThreads;
    +
    +  public BatchInputSplit() {
    +    ranges = Collections.emptyList();
    +  }
    +
    +  public BatchInputSplit(BatchInputSplit split) throws IOException {
    +    super(split);
    +    this.setRanges(split.getRanges());
    +  }
    +
    +  protected BatchInputSplit(String table, String tableId, Collection<Range> ranges,
String[] locations) {
    +    super(table, tableId, locations);
    +    this.ranges = ranges;
    +  }
    +
    +  public float getProgress(Key currentKey) {
    +    if (currentKey == null)
    +      return 0f;
    +    for (Range range : ranges) {
    --- End diff --
    
    Of course, then I think of something. Perhaps keep a sum of the progress over each Range
and then return the average across the progress of each Range. It's not guaranteed to be right
since we may never get this method called with each Range, but it might be close  enough.
The important part is ensuring that this number will be increasing.


> 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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