org.apache.hadoop.mapred.lib.db
Class DBInputFormat.DBRecordReader

java.lang.Object
  org.apache.hadoop.mapred.lib.db.DBInputFormat.DBRecordReader

All Implemented Interfaces:

RecordReader<LongWritable,T>

Enclosing class:

DBInputFormat<T extends DBWritable>

protected class DBInputFormat.DBRecordReader
extends Object
implements RecordReader<LongWritable,T>

A RecordReader that reads records from a SQL table. Emits LongWritables containing the record number as key and DBWritables as value.

Constructor Summary

protected

DBInputFormat.DBRecordReader(DBInputFormat.DBInputSplit split, Class<T> inputClass, JobConf job)

Method Summary

void	close() Close this InputSplit to future operations.
LongWritable	createKey() Create an object of the appropriate type to be used as a key.
T	createValue() Create an object of the appropriate type to be used as a value.
long	getPos() Returns the current position in the input.
float	getProgress() How much of the input has the RecordReader consumed i.e.
protected String	getSelectQuery() Returns the query for selecting the records, subclasses can override this for custom behaviour.
boolean	next(LongWritable key, T value) Reads the next key/value pair from the input for processing.

Methods inherited from class java.lang.Object

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

Constructor Detail

DBInputFormat.DBRecordReader

protected DBInputFormat.DBRecordReader(DBInputFormat.DBInputSplit split,
                                       Class<T> inputClass,
                                       JobConf job)
                                throws SQLException

Parameters:

split - The InputSplit to read data for

Throws:

SQLException

Method Detail

getSelectQuery

protected String getSelectQuery()

Returns the query for selecting the records, subclasses can override this for custom behaviour.

close

public void close()
           throws IOException

Close this InputSplit to future operations.

Specified by:

close in interface RecordReader<LongWritable,T extends DBWritable>

Throws:

IOException

createKey

public LongWritable createKey()

Create an object of the appropriate type to be used as a key.

Specified by:

createKey in interface RecordReader<LongWritable,T extends DBWritable>

Returns:

a new key object.

createValue

public T createValue()

Create an object of the appropriate type to be used as a value.

Specified by:

createValue in interface RecordReader<LongWritable,T extends DBWritable>

Returns:

a new value object.

getPos

public long getPos()
            throws IOException

Returns the current position in the input.

Specified by:

getPos in interface RecordReader<LongWritable,T extends DBWritable>

Returns:

the current position in the input.

Throws:

IOException

getProgress

public float getProgress()
                  throws IOException

How much of the input has the RecordReader consumed i.e. has been processed by?

Specified by:

getProgress in interface RecordReader<LongWritable,T extends DBWritable>

Returns:

progress from 0.0 to 1.0.

Throws:

IOException

next

public boolean next(LongWritable key,
                    T value)
             throws IOException

Reads the next key/value pair from the input for processing.

Specified by:

next in interface RecordReader<LongWritable,T extends DBWritable>

Parameters:

key - the key to read data into

value - the value to read data into

Returns:

true iff a key/value was read, false if at EOF

Throws:

IOException