org.apache.hadoop.mapred.lib.db

类 DBInputFormat.DBRecordReader

java.lang.Object

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

所有已实现的接口:

RecordReader<LongWritable,T>

封闭类:

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.

构造器概要

构造器

限定符	构造器和说明
protected	DBInputFormat.DBRecordReader(DBInputFormat.DBInputSplit split, Class<T> inputClass, JobConf job)

方法概要

方法

限定符和类型	方法和说明
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.

从类继承的方法 java.lang.Object

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

构造器详细资料

DBInputFormat.DBRecordReader

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

参数:

split - The InputSplit to read data for

抛出:

SQLException

方法详细资料

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.

指定者:

close 在接口中 RecordReader<LongWritable,T extends DBWritable>

抛出:

IOException

createKey

public LongWritable createKey()

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

指定者:

createKey 在接口中 RecordReader<LongWritable,T extends DBWritable>

返回:

a new key object.

createValue

public T createValue()

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

指定者:

createValue 在接口中 RecordReader<LongWritable,T extends DBWritable>

返回:

a new value object.

getPos

public long getPos()
            throws IOException

Returns the current position in the input.

指定者:

getPos 在接口中 RecordReader<LongWritable,T extends DBWritable>

返回:

the current position in the input.

抛出:

IOException

getProgress

public float getProgress()
                  throws IOException

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

指定者:

getProgress 在接口中 RecordReader<LongWritable,T extends DBWritable>

返回:

progress from 0.0 to 1.0.

抛出:

IOException

next

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

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

指定者:

next 在接口中 RecordReader<LongWritable,T extends DBWritable>

参数:

key - the key to read data into

value - the value to read data into

返回:

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

抛出:

IOException