org.apache.hadoop.mapred.lib

クラス NLineInputFormat

java.lang.Object

org.apache.hadoop.mapred.FileInputFormat<LongWritable,Text>

org.apache.hadoop.mapred.lib.NLineInputFormat

すべての実装されたインタフェース:

InputFormat<LongWritable,Text>, JobConfigurable

@InterfaceAudience.Public
 @InterfaceStability.Stable
public class NLineInputFormat
extends FileInputFormat<LongWritable,Text>
implements JobConfigurable

NLineInputFormat which splits N lines of input as one split. In many "pleasantly" parallel applications, each process/mapper processes the same input file (s), but with computations are controlled by different parameters.(Referred to as "parameter sweeps"). One way to achieve this, is to specify a set of parameters (one set per line) as input in a control file (which is the input path to the map-reduce application, where as the input dataset is specified via a config variable in JobConf.). The NLineInputFormat can be used in such applications, that splits the input file such that by default, one line is fed as a value to one map task, and key is the offset. i.e. (k,v) is (LongWritable, Text). The location hints will span the whole mapred cluster.

フィールドのサマリー

クラスから継承されたフィールド org.apache.hadoop.mapred.FileInputFormat

INPUT_DIR_RECURSIVE, LOG, NUM_INPUT_FILES

コンストラクタのサマリー

コンストラクタ

コンストラクタと説明
NLineInputFormat()

メソッドのサマリー

修飾子とタイプ	メソッドと説明
void	configure(JobConf conf) Initializes a new instance from a JobConf.
protected static FileSplit	createFileSplit(Path fileName, long begin, long length) NLineInputFormat uses LineRecordReader, which always reads (and consumes) at least one character out of its upper split boundary.
RecordReader<LongWritable,Text>	getRecordReader(InputSplit genericSplit, JobConf job, Reporter reporter) Get the RecordReader for the given InputSplit.
InputSplit[]	getSplits(JobConf job, int numSplits) Logically splits the set of input files for the job, splits N lines of the input as one split.

クラスから継承されたメソッド org.apache.hadoop.mapred.FileInputFormat

addInputPath, addInputPathRecursively, addInputPaths, computeSplitSize, getBlockIndex, getInputPathFilter, getInputPaths, getSplitHosts, isSplitable, listStatus, makeSplit, makeSplit, setInputPathFilter, setInputPaths, setInputPaths, setMinSplitSize

クラスから継承されたメソッド java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

コンストラクタの詳細

NLineInputFormat

public NLineInputFormat()

メソッドの詳細

getRecordReader

public RecordReader<LongWritable,Text> getRecordReader(InputSplit genericSplit,
                                                       JobConf job,
                                                       Reporter reporter)
                                                throws IOException

インタフェースからコピーされた説明: InputFormat

Get the RecordReader for the given InputSplit.

It is the responsibility of the RecordReader to respect record boundaries while processing the logical split to present a record-oriented view to the individual task.

定義:

getRecordReader インタフェース内 InputFormat<LongWritable,Text>

定義:

getRecordReader クラス内 FileInputFormat<LongWritable,Text>

パラメータ:

genericSplit - the InputSplit

job - the job that this split belongs to

戻り値:

a RecordReader

例外:

IOException

getSplits

public InputSplit[] getSplits(JobConf job,
                              int numSplits)
                       throws IOException

Logically splits the set of input files for the job, splits N lines of the input as one split.

定義:

getSplits インタフェース内 InputFormat<LongWritable,Text>

オーバーライド:

getSplits クラス内 FileInputFormat<LongWritable,Text>

パラメータ:

job - job configuration.

numSplits - the desired number of splits, a hint.

戻り値:

an array of InputSplits for the job.

例外:

IOException

関連項目:

FileInputFormat.getSplits(JobConf, int)

configure

public void configure(JobConf conf)

インタフェースからコピーされた説明: JobConfigurable

Initializes a new instance from a JobConf.

定義:

configure インタフェース内 JobConfigurable

パラメータ:

conf - the configuration

createFileSplit

protected static FileSplit createFileSplit(Path fileName,
                                           long begin,
                                           long length)

NLineInputFormat uses LineRecordReader, which always reads (and consumes) at least one character out of its upper split boundary. So to make sure that each mapper gets N lines, we move back the upper split limits of each split by one character here.

パラメータ:

fileName - Path of file

begin - the position of the first byte in the file to process

length - number of bytes in InputSplit

戻り値:

FileSplit