org.apache.hadoop.mapred
Interface InputFormat

All Known Implementing Classes:

FileInputFormat, InputFormatBase, KeyValueTextInputFormat, SequenceFileAsTextInputFormat, SequenceFileInputFilter, SequenceFileInputFormat, StreamInputFormat, TextInputFormat

public interface InputFormat

An input data format. Input files are stored in a FileSystem. The processing of an input file may be split across multiple machines. Files are processed as sequences of records, implementing RecordReader. Files must thus be split on record boundaries.

Method Summary

RecordReader	getRecordReader(InputSplit split, JobConf job, Reporter reporter) Construct a RecordReader for a FileSplit.
InputSplit[]	getSplits(JobConf job, int numSplits) Splits a set of input files.
void	validateInput(JobConf job) Are the input directories valid? This method is used to test the input directories when a job is submitted so that the framework can fail early with a useful error message when the input directory does not exist.

Method Detail

validateInput

void validateInput(JobConf job)
                   throws IOException

Are the input directories valid? This method is used to test the input directories when a job is submitted so that the framework can fail early with a useful error message when the input directory does not exist.

Parameters:

job - the job to check

Throws:

InvalidInputException - if the job does not have valid input

IOException

getSplits

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

Splits a set of input files. One split is created per map task.

Parameters:

job - the job whose input files are to be split

numSplits - the desired number of splits

Returns:

the splits

Throws:

IOException

getRecordReader

RecordReader getRecordReader(InputSplit split,
                             JobConf job,
                             Reporter reporter)
                             throws IOException

Construct a RecordReader for a FileSplit.

Parameters:

split - the InputSplit

job - the job that this split belongs to

Returns:

a RecordReader

Throws:

IOException