MAPREDUCE-5656. bzip2 codec can drop records when reading data in splits. Contributed by Jason Lowe
git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1549705 13f79535-47bb-0310-9956-ffa450edef68
This commit is contained in:
parent
87a6db45b7
commit
18d99c12c3
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@ -175,6 +175,11 @@ public class LineReader implements Closeable {
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}
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}
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protected int fillBuffer(InputStream in, byte[] buffer, boolean inDelimiter)
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throws IOException {
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return in.read(buffer);
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}
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/**
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* Read a line terminated by one of CR, LF, or CRLF.
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*/
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@ -208,7 +213,7 @@ public class LineReader implements Closeable {
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if (prevCharCR) {
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++bytesConsumed; //account for CR from previous read
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}
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bufferLength = in.read(buffer);
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bufferLength = fillBuffer(in, buffer, prevCharCR);
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if (bufferLength <= 0) {
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break; // EOF
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}
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@ -296,7 +301,7 @@ public class LineReader implements Closeable {
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int startPosn = bufferPosn; // Start from previous end position
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if (bufferPosn >= bufferLength) {
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startPosn = bufferPosn = 0;
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bufferLength = in.read(buffer);
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bufferLength = fillBuffer(in, buffer, ambiguousByteCount > 0);
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if (bufferLength <= 0) {
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str.append(recordDelimiterBytes, 0, ambiguousByteCount);
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break; // EOF
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@ -231,6 +231,9 @@ Release 2.4.0 - UNRELEASED
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MAPREDUCE-5632. TestRMContainerAllocator#testUpdatedNodes fails (jeagles)
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MAPREDUCE-5656. bzip2 codec can drop records when reading data in splits
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(jlowe)
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Release 2.3.0 - UNRELEASED
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INCOMPATIBLE CHANGES
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@ -36,6 +36,8 @@ import org.apache.hadoop.io.compress.CompressionCodecFactory;
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import org.apache.hadoop.io.compress.Decompressor;
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import org.apache.hadoop.io.compress.SplitCompressionInputStream;
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import org.apache.hadoop.io.compress.SplittableCompressionCodec;
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import org.apache.hadoop.mapreduce.lib.input.CompressedSplitLineReader;
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import org.apache.hadoop.mapreduce.lib.input.SplitLineReader;
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import org.apache.commons.logging.LogFactory;
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import org.apache.commons.logging.Log;
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@ -52,7 +54,7 @@ public class LineRecordReader implements RecordReader<LongWritable, Text> {
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private long start;
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private long pos;
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private long end;
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private LineReader in;
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private SplitLineReader in;
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private FSDataInputStream fileIn;
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private final Seekable filePosition;
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int maxLineLength;
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@ -111,17 +113,18 @@ public class LineRecordReader implements RecordReader<LongWritable, Text> {
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((SplittableCompressionCodec)codec).createInputStream(
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fileIn, decompressor, start, end,
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SplittableCompressionCodec.READ_MODE.BYBLOCK);
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in = new LineReader(cIn, job, recordDelimiter);
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in = new CompressedSplitLineReader(cIn, job, recordDelimiter);
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start = cIn.getAdjustedStart();
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end = cIn.getAdjustedEnd();
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filePosition = cIn; // take pos from compressed stream
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} else {
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in = new LineReader(codec.createInputStream(fileIn, decompressor), job, recordDelimiter);
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in = new SplitLineReader(codec.createInputStream(fileIn,
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decompressor), job, recordDelimiter);
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filePosition = fileIn;
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}
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} else {
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fileIn.seek(start);
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in = new LineReader(fileIn, job, recordDelimiter);
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in = new SplitLineReader(fileIn, job, recordDelimiter);
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filePosition = fileIn;
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}
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// If this is not the first split, we always throw away first record
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@ -141,7 +144,7 @@ public class LineRecordReader implements RecordReader<LongWritable, Text> {
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public LineRecordReader(InputStream in, long offset, long endOffset,
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int maxLineLength, byte[] recordDelimiter) {
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this.maxLineLength = maxLineLength;
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this.in = new LineReader(in, recordDelimiter);
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this.in = new SplitLineReader(in, recordDelimiter);
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this.start = offset;
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this.pos = offset;
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this.end = endOffset;
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@ -159,7 +162,7 @@ public class LineRecordReader implements RecordReader<LongWritable, Text> {
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throws IOException{
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this.maxLineLength = job.getInt(org.apache.hadoop.mapreduce.lib.input.
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LineRecordReader.MAX_LINE_LENGTH, Integer.MAX_VALUE);
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this.in = new LineReader(in, job, recordDelimiter);
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this.in = new SplitLineReader(in, job, recordDelimiter);
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this.start = offset;
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this.pos = offset;
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this.end = endOffset;
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@ -200,7 +203,7 @@ public class LineRecordReader implements RecordReader<LongWritable, Text> {
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// We always read one extra line, which lies outside the upper
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// split limit i.e. (end - 1)
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while (getFilePosition() <= end) {
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while (getFilePosition() <= end || in.needAdditionalRecordAfterSplit()) {
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key.set(pos);
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int newSize = in.readLine(value, maxLineLength,
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@ -0,0 +1,168 @@
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/**
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* Licensed to the Apache Software Foundation (ASF) under one
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* or more contributor license agreements. See the NOTICE file
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* distributed with this work for additional information
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* regarding copyright ownership. The ASF licenses this file
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* to you under the Apache License, Version 2.0 (the
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* "License"); you may not use this file except in compliance
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* with the License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package org.apache.hadoop.mapreduce.lib.input;
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import java.io.IOException;
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import java.io.InputStream;
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import org.apache.hadoop.classification.InterfaceAudience;
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import org.apache.hadoop.classification.InterfaceStability;
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import org.apache.hadoop.conf.Configuration;
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import org.apache.hadoop.io.Text;
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import org.apache.hadoop.io.compress.SplitCompressionInputStream;
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/**
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* Line reader for compressed splits
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*
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* Reading records from a compressed split is tricky, as the
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* LineRecordReader is using the reported compressed input stream
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* position directly to determine when a split has ended. In addition the
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* compressed input stream is usually faking the actual byte position, often
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* updating it only after the first compressed block after the split is
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* accessed.
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*
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* Depending upon where the last compressed block of the split ends relative
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* to the record delimiters it can be easy to accidentally drop the last
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* record or duplicate the last record between this split and the next.
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*
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* Split end scenarios:
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*
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* 1) Last block of split ends in the middle of a record
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* Nothing special that needs to be done here, since the compressed input
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* stream will report a position after the split end once the record
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* is fully read. The consumer of the next split will discard the
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* partial record at the start of the split normally, and no data is lost
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* or duplicated between the splits.
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*
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* 2) Last block of split ends in the middle of a delimiter
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* The line reader will continue to consume bytes into the next block to
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* locate the end of the delimiter. If a custom delimiter is being used
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* then the next record must be read by this split or it will be dropped.
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* The consumer of the next split will not recognize the partial
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* delimiter at the beginning of its split and will discard it along with
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* the next record.
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*
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* However for the default delimiter processing there is a special case
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* because CR, LF, and CRLF are all valid record delimiters. If the
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* block ends with a CR then the reader must peek at the next byte to see
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* if it is an LF and therefore part of the same record delimiter.
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* Peeking at the next byte is an access to the next block and triggers
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* the stream to report the end of the split. There are two cases based
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* on the next byte:
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*
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* A) The next byte is LF
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* The split needs to end after the current record is returned. The
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* consumer of the next split will discard the first record, which
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* is degenerate since LF is itself a delimiter, and start consuming
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* records after that byte. If the current split tries to read
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* another record then the record will be duplicated between splits.
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*
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* B) The next byte is not LF
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* The current record will be returned but the stream will report
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* the split has ended due to the peek into the next block. If the
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* next record is not read then it will be lost, as the consumer of
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* the next split will discard it before processing subsequent
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* records. Therefore the next record beyond the reported split end
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* must be consumed by this split to avoid data loss.
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*
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* 3) Last block of split ends at the beginning of a delimiter
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* This is equivalent to case 1, as the reader will consume bytes into
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* the next block and trigger the end of the split. No further records
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* should be read as the consumer of the next split will discard the
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* (degenerate) record at the beginning of its split.
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*
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* 4) Last block of split ends at the end of a delimiter
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* Nothing special needs to be done here. The reader will not start
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* examining the bytes into the next block until the next record is read,
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* so the stream will not report the end of the split just yet. Once the
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* next record is read then the next block will be accessed and the
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* stream will indicate the end of the split. The consumer of the next
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* split will correctly discard the first record of its split, and no
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* data is lost or duplicated.
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*
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* If the default delimiter is used and the block ends at a CR then this
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* is treated as case 2 since the reader does not yet know without
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* looking at subsequent bytes whether the delimiter has ended.
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*
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* NOTE: It is assumed that compressed input streams *never* return bytes from
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* multiple compressed blocks from a single read. Failure to do so will
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* violate the buffering performed by this class, as it will access
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* bytes into the next block after the split before returning all of the
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* records from the previous block.
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*/
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@InterfaceAudience.Private
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@InterfaceStability.Unstable
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public class CompressedSplitLineReader extends SplitLineReader {
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SplitCompressionInputStream scin;
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private boolean usingCRLF;
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private boolean needAdditionalRecord = false;
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private boolean finished = false;
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public CompressedSplitLineReader(SplitCompressionInputStream in,
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Configuration conf,
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byte[] recordDelimiterBytes)
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throws IOException {
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super(in, conf, recordDelimiterBytes);
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scin = in;
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usingCRLF = (recordDelimiterBytes == null);
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}
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@Override
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protected int fillBuffer(InputStream in, byte[] buffer, boolean inDelimiter)
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throws IOException {
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int bytesRead = in.read(buffer);
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// If the split ended in the middle of a record delimiter then we need
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// to read one additional record, as the consumer of the next split will
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// not recognize the partial delimiter as a record.
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// However if using the default delimiter and the next character is a
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// linefeed then next split will treat it as a delimiter all by itself
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// and the additional record read should not be performed.
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if (inDelimiter && bytesRead > 0) {
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if (usingCRLF) {
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needAdditionalRecord = (buffer[0] != '\n');
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} else {
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needAdditionalRecord = true;
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}
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}
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return bytesRead;
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}
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@Override
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public int readLine(Text str, int maxLineLength, int maxBytesToConsume)
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throws IOException {
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int bytesRead = 0;
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if (!finished) {
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// only allow at most one more record to be read after the stream
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// reports the split ended
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if (scin.getPos() > scin.getAdjustedEnd()) {
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finished = true;
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}
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bytesRead = super.readLine(str, maxLineLength, maxBytesToConsume);
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}
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return bytesRead;
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}
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@Override
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public boolean needAdditionalRecordAfterSplit() {
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return !finished && needAdditionalRecord;
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}
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}
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@ -38,7 +38,6 @@ import org.apache.hadoop.io.compress.Decompressor;
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import org.apache.hadoop.mapreduce.InputSplit;
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import org.apache.hadoop.mapreduce.RecordReader;
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import org.apache.hadoop.mapreduce.TaskAttemptContext;
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import org.apache.hadoop.util.LineReader;
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import org.apache.commons.logging.LogFactory;
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import org.apache.commons.logging.Log;
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@ -55,7 +54,7 @@ public class LineRecordReader extends RecordReader<LongWritable, Text> {
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private long start;
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private long pos;
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private long end;
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private LineReader in;
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private SplitLineReader in;
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private FSDataInputStream fileIn;
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private Seekable filePosition;
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private int maxLineLength;
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@ -94,33 +93,19 @@ public class LineRecordReader extends RecordReader<LongWritable, Text> {
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((SplittableCompressionCodec)codec).createInputStream(
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fileIn, decompressor, start, end,
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SplittableCompressionCodec.READ_MODE.BYBLOCK);
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if (null == this.recordDelimiterBytes){
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in = new LineReader(cIn, job);
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} else {
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in = new LineReader(cIn, job, this.recordDelimiterBytes);
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}
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in = new CompressedSplitLineReader(cIn, job,
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this.recordDelimiterBytes);
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start = cIn.getAdjustedStart();
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end = cIn.getAdjustedEnd();
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filePosition = cIn;
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} else {
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if (null == this.recordDelimiterBytes) {
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in = new LineReader(codec.createInputStream(fileIn, decompressor),
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job);
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} else {
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in = new LineReader(codec.createInputStream(fileIn,
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decompressor), job, this.recordDelimiterBytes);
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}
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in = new SplitLineReader(codec.createInputStream(fileIn,
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decompressor), job, this.recordDelimiterBytes);
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filePosition = fileIn;
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}
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} else {
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fileIn.seek(start);
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if (null == this.recordDelimiterBytes){
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in = new LineReader(fileIn, job);
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} else {
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in = new LineReader(fileIn, job, this.recordDelimiterBytes);
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}
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in = new SplitLineReader(fileIn, job, this.recordDelimiterBytes);
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filePosition = fileIn;
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}
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// If this is not the first split, we always throw away first record
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@ -160,7 +145,7 @@ public class LineRecordReader extends RecordReader<LongWritable, Text> {
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int newSize = 0;
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// We always read one extra line, which lies outside the upper
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// split limit i.e. (end - 1)
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while (getFilePosition() <= end) {
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while (getFilePosition() <= end || in.needAdditionalRecordAfterSplit()) {
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newSize = in.readLine(value, maxLineLength,
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Math.max(maxBytesToConsume(pos), maxLineLength));
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pos += newSize;
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|
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@ -0,0 +1,43 @@
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/**
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* Licensed to the Apache Software Foundation (ASF) under one
|
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* 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
|
||||
*
|
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* http://www.apache.org/licenses/LICENSE-2.0
|
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*
|
||||
* 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.
|
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*/
|
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|
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package org.apache.hadoop.mapreduce.lib.input;
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import java.io.IOException;
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import java.io.InputStream;
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import org.apache.hadoop.classification.InterfaceAudience;
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import org.apache.hadoop.classification.InterfaceStability;
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import org.apache.hadoop.conf.Configuration;
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@InterfaceAudience.Private
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@InterfaceStability.Unstable
|
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public class SplitLineReader extends org.apache.hadoop.util.LineReader {
|
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public SplitLineReader(InputStream in, byte[] recordDelimiterBytes) {
|
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super(in, recordDelimiterBytes);
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}
|
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|
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public SplitLineReader(InputStream in, Configuration conf,
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byte[] recordDelimiterBytes) throws IOException {
|
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super(in, conf, recordDelimiterBytes);
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}
|
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|
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public boolean needAdditionalRecordAfterSplit() {
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return false;
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}
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}
|
|
@ -0,0 +1,100 @@
|
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/**
|
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* 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.
|
||||
*/
|
||||
|
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package org.apache.hadoop.mapred;
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import static org.junit.Assert.assertEquals;
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import static org.junit.Assert.assertNotNull;
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import static org.junit.Assert.assertTrue;
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import java.io.File;
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import java.io.IOException;
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import java.net.URL;
|
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|
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import org.apache.hadoop.conf.Configuration;
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import org.apache.hadoop.fs.Path;
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import org.apache.hadoop.io.LongWritable;
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import org.apache.hadoop.io.Text;
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import org.junit.Test;
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|
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public class TestLineRecordReader {
|
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|
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private void testSplitRecords(String testFileName, long firstSplitLength)
|
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throws IOException {
|
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URL testFileUrl = getClass().getClassLoader().getResource(testFileName);
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assertNotNull("Cannot find " + testFileName, testFileUrl);
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File testFile = new File(testFileUrl.getFile());
|
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long testFileSize = testFile.length();
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Path testFilePath = new Path(testFile.getAbsolutePath());
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Configuration conf = new Configuration();
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conf.setInt(org.apache.hadoop.mapreduce.lib.input.
|
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LineRecordReader.MAX_LINE_LENGTH, Integer.MAX_VALUE);
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assertTrue("unexpected test data at " + testFile,
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testFileSize > firstSplitLength);
|
||||
|
||||
// read the data without splitting to count the records
|
||||
FileSplit split = new FileSplit(testFilePath, 0, testFileSize,
|
||||
(String[])null);
|
||||
LineRecordReader reader = new LineRecordReader(conf, split);
|
||||
LongWritable key = new LongWritable();
|
||||
Text value = new Text();
|
||||
int numRecordsNoSplits = 0;
|
||||
while (reader.next(key, value)) {
|
||||
++numRecordsNoSplits;
|
||||
}
|
||||
reader.close();
|
||||
|
||||
// count the records in the first split
|
||||
split = new FileSplit(testFilePath, 0, firstSplitLength, (String[])null);
|
||||
reader = new LineRecordReader(conf, split);
|
||||
int numRecordsFirstSplit = 0;
|
||||
while (reader.next(key, value)) {
|
||||
++numRecordsFirstSplit;
|
||||
}
|
||||
reader.close();
|
||||
|
||||
// count the records in the second split
|
||||
split = new FileSplit(testFilePath, firstSplitLength,
|
||||
testFileSize - firstSplitLength, (String[])null);
|
||||
reader = new LineRecordReader(conf, split);
|
||||
int numRecordsRemainingSplits = 0;
|
||||
while (reader.next(key, value)) {
|
||||
++numRecordsRemainingSplits;
|
||||
}
|
||||
reader.close();
|
||||
|
||||
assertEquals("Unexpected number of records in bzip2 compressed split",
|
||||
numRecordsNoSplits, numRecordsFirstSplit + numRecordsRemainingSplits);
|
||||
}
|
||||
|
||||
@Test
|
||||
public void testBzip2SplitEndsAtCR() throws IOException {
|
||||
// the test data contains a carriage-return at the end of the first
|
||||
// split which ends at compressed offset 136498 and the next
|
||||
// character is not a linefeed
|
||||
testSplitRecords("blockEndingInCR.txt.bz2", 136498);
|
||||
}
|
||||
|
||||
@Test
|
||||
public void testBzip2SplitEndsAtCRThenLF() throws IOException {
|
||||
// the test data contains a carriage-return at the end of the first
|
||||
// split which ends at compressed offset 136498 and the next
|
||||
// character is a linefeed
|
||||
testSplitRecords("blockEndingInCRThenLF.txt.bz2", 136498);
|
||||
}
|
||||
}
|
|
@ -0,0 +1,104 @@
|
|||
/**
|
||||
* 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.hadoop.mapreduce.lib.input;
|
||||
|
||||
import static org.junit.Assert.assertEquals;
|
||||
import static org.junit.Assert.assertNotNull;
|
||||
import static org.junit.Assert.assertTrue;
|
||||
|
||||
import java.io.File;
|
||||
import java.io.IOException;
|
||||
import java.net.URL;
|
||||
|
||||
import org.apache.hadoop.conf.Configuration;
|
||||
import org.apache.hadoop.fs.Path;
|
||||
import org.apache.hadoop.mapreduce.TaskAttemptContext;
|
||||
import org.apache.hadoop.mapreduce.TaskAttemptID;
|
||||
import org.apache.hadoop.mapreduce.task.TaskAttemptContextImpl;
|
||||
import org.junit.Test;
|
||||
|
||||
public class TestLineRecordReader {
|
||||
|
||||
private void testSplitRecords(String testFileName, long firstSplitLength)
|
||||
throws IOException {
|
||||
URL testFileUrl = getClass().getClassLoader().getResource(testFileName);
|
||||
assertNotNull("Cannot find " + testFileName, testFileUrl);
|
||||
File testFile = new File(testFileUrl.getFile());
|
||||
long testFileSize = testFile.length();
|
||||
Path testFilePath = new Path(testFile.getAbsolutePath());
|
||||
Configuration conf = new Configuration();
|
||||
conf.setInt(org.apache.hadoop.mapreduce.lib.input.
|
||||
LineRecordReader.MAX_LINE_LENGTH, Integer.MAX_VALUE);
|
||||
assertTrue("unexpected test data at " + testFile,
|
||||
testFileSize > firstSplitLength);
|
||||
|
||||
TaskAttemptContext context = new TaskAttemptContextImpl(conf, new TaskAttemptID());
|
||||
|
||||
// read the data without splitting to count the records
|
||||
FileSplit split = new FileSplit(testFilePath, 0, testFileSize,
|
||||
(String[])null);
|
||||
LineRecordReader reader = new LineRecordReader();
|
||||
reader.initialize(split, context);
|
||||
int numRecordsNoSplits = 0;
|
||||
while (reader.nextKeyValue()) {
|
||||
++numRecordsNoSplits;
|
||||
}
|
||||
reader.close();
|
||||
|
||||
// count the records in the first split
|
||||
split = new FileSplit(testFilePath, 0, firstSplitLength, (String[])null);
|
||||
reader = new LineRecordReader();
|
||||
reader.initialize(split, context);
|
||||
int numRecordsFirstSplit = 0;
|
||||
while (reader.nextKeyValue()) {
|
||||
++numRecordsFirstSplit;
|
||||
}
|
||||
reader.close();
|
||||
|
||||
// count the records in the second split
|
||||
split = new FileSplit(testFilePath, firstSplitLength,
|
||||
testFileSize - firstSplitLength, (String[])null);
|
||||
reader = new LineRecordReader();
|
||||
reader.initialize(split, context);
|
||||
int numRecordsRemainingSplits = 0;
|
||||
while (reader.nextKeyValue()) {
|
||||
++numRecordsRemainingSplits;
|
||||
}
|
||||
reader.close();
|
||||
|
||||
assertEquals("Unexpected number of records in bzip2 compressed split",
|
||||
numRecordsNoSplits, numRecordsFirstSplit + numRecordsRemainingSplits);
|
||||
}
|
||||
|
||||
@Test
|
||||
public void testBzip2SplitEndsAtCR() throws IOException {
|
||||
// the test data contains a carriage-return at the end of the first
|
||||
// split which ends at compressed offset 136498 and the next
|
||||
// character is not a linefeed
|
||||
testSplitRecords("blockEndingInCR.txt.bz2", 136498);
|
||||
}
|
||||
|
||||
@Test
|
||||
public void testBzip2SplitEndsAtCRThenLF() throws IOException {
|
||||
// the test data contains a carriage-return at the end of the first
|
||||
// split which ends at compressed offset 136498 and the next
|
||||
// character is a linefeed
|
||||
testSplitRecords("blockEndingInCRThenLF.txt.bz2", 136498);
|
||||
}
|
||||
}
|
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Reference in New Issue