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https://issues.apache.org/jira/browse/ACCUMULO-3602?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14485514#comment-14485514
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ASF GitHub Bot commented on ACCUMULO-3602:
------------------------------------------
Github user echeipesh commented on a diff in the pull request:
https://github.com/apache/accumulo/pull/25#discussion_r27988729
--- Diff:
core/src/main/java/org/apache/accumulo/core/client/mapred/AbstractInputFormat.java
---
@@ -384,7 +387,21 @@ public static InputTableConfig
getInputTableConfig(JobConf job, String tableName
protected abstract static class AbstractRecordReader<K,V> implements
RecordReader<K,V> {
protected long numKeysRead;
protected Iterator<Map.Entry<Key,Value>> scannerIterator;
- protected RangeInputSplit split;
+ protected
org.apache.accumulo.core.client.mapreduce.impl.AccumuloInputSplit split;
+ protected ScannerBase scannerBase;
+
+ /**
+ * Configures the iterators on a scanner for the given table name.
+ *
+ * @param job
+ * the Hadoop job configuration
+ * @param scanner
+ * the scanner for which to configure the iterators
+ * @param tableName
+ * the table name for which the scanner is configured
+ * @since 1.7.0
+ */
+ protected abstract void setupIterators(JobConf job, ScannerBase
scanner, String tableName, AccumuloInputSplit split);
--- End diff --
Actually that's just factored out of old `RangeInputSplit`. Looking over
the code there doesn't seem to be a reason for it. All of those options are
coming from `InputTableConfig` which, as you say, is deserialized from
`JobContext`. Looking over the code there really isn't any hard reason for that
(and most fields in `AccumuloInputSplit`) to be there. Although I think it
makes it a little easier to reason about.
> 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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