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https://issues.apache.org/jira/browse/ACCUMULO-3602?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14392028#comment-14392028
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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_r27629523
--- 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 --
Sadly, this isn't really representative like it was for a single Range per
InputSplit. There will be a semblance of ordering (as Accumulo is going to be
doing batches under the hood), but there's no real progress you can identify
out of keys from a BatchScanner. The only realistic approximation I can think
of is based off of some stats we store in the metadata table, but I don't think
that's realistic in this changeset.
I can't think of a reliable way to do this computation. If that's the case,
I'd be apt to just `return 0` and mark it as a TODO
> 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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