org.apache.hadoop.mapreduce.lib.db

类 DBRecordReader<T extends DBWritable>

java.lang.Object

org.apache.hadoop.mapreduce.RecordReader<LongWritable,T>

org.apache.hadoop.mapreduce.lib.db.DBRecordReader<T>

所有已实现的接口:

Closeable, AutoCloseable

直接已知子类:

DataDrivenDBRecordReader, MySQLDBRecordReader, OracleDBRecordReader

@InterfaceAudience.Public
@InterfaceStability.Evolving
public class DBRecordReader<T extends DBWritable>
extends RecordReader<LongWritable,T>

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

字段概要

字段

限定符和类型	字段和说明
protected PreparedStatement	statement

构造器概要

构造器

构造器和说明
DBRecordReader(DBInputFormat.DBInputSplit split, Class<T> inputClass, Configuration conf, Connection conn, DBConfiguration dbConfig, String cond, String[] fields, String table)

方法概要

方法

限定符和类型	方法和说明
void	close() Close the record reader.
T	createValue() 已过时。
protected ResultSet	executeQuery(String query)
protected String	getConditions()
protected Connection	getConnection()
LongWritable	getCurrentKey() Get the current key
T	getCurrentValue() Get the current value.
protected DBConfiguration	getDBConf()
protected String[]	getFieldNames()
long	getPos() 已过时。
float	getProgress() The current progress of the record reader through its data.
protected String	getSelectQuery() Returns the query for selecting the records, subclasses can override this for custom behaviour.
protected DBInputFormat.DBInputSplit	getSplit()
protected PreparedStatement	getStatement()
protected String	getTableName()
void	initialize(InputSplit split, TaskAttemptContext context) Called once at initialization.
boolean	next(LongWritable key, T value) 已过时。 Use nextKeyValue()
boolean	nextKeyValue() Read the next key, value pair.
protected void	setStatement(PreparedStatement stmt)

从类继承的方法 java.lang.Object

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

字段详细资料

statement

protected PreparedStatement statement

构造器详细资料

DBRecordReader

public DBRecordReader(DBInputFormat.DBInputSplit split,
              Class<T> inputClass,
              Configuration conf,
              Connection conn,
              DBConfiguration dbConfig,
              String cond,
              String[] fields,
              String table)
               throws SQLException

参数:

split - The InputSplit to read data for

抛出:

SQLException

方法详细资料

executeQuery

protected ResultSet executeQuery(String query)
                          throws SQLException

抛出:

SQLException

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 the record reader.

指定者:

close 在接口中 Closeable

指定者:

close 在接口中 AutoCloseable

指定者:

close 在类中 RecordReader<LongWritable,T extends DBWritable>

抛出:

IOException

initialize

public void initialize(InputSplit split,
              TaskAttemptContext context)
                throws IOException,
                       InterruptedException

从类复制的说明: RecordReader

Called once at initialization.

指定者:

initialize 在类中 RecordReader<LongWritable,T extends DBWritable>

参数:

split - the split that defines the range of records to read

context - the information about the task

抛出:

IOException

InterruptedException

getCurrentKey

public LongWritable getCurrentKey()

Get the current key

指定者:

getCurrentKey 在类中 RecordReader<LongWritable,T extends DBWritable>

返回:

the current key or null if there is no current key

getCurrentValue

public T getCurrentValue()

Get the current value.

指定者:

getCurrentValue 在类中 RecordReader<LongWritable,T extends DBWritable>

返回:

the object that was read

createValue

@Deprecated
public T createValue()

已过时。

getPos

@Deprecated
public long getPos()
            throws IOException

已过时。

抛出:

IOException

next

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

已过时。 Use nextKeyValue()

抛出:

IOException

getProgress

public float getProgress()
                  throws IOException

The current progress of the record reader through its data.

指定者:

getProgress 在类中 RecordReader<LongWritable,T extends DBWritable>

返回:

a number between 0.0 and 1.0 that is the fraction of the data read

抛出:

IOException

nextKeyValue

public boolean nextKeyValue()
                     throws IOException

Read the next key, value pair.

指定者:

nextKeyValue 在类中 RecordReader<LongWritable,T extends DBWritable>

返回:

true if a key/value pair was read

抛出:

IOException

getSplit

protected DBInputFormat.DBInputSplit getSplit()

getFieldNames

protected String[] getFieldNames()

getTableName

protected String getTableName()

getConditions

protected String getConditions()

getDBConf

protected DBConfiguration getDBConf()

getConnection

protected Connection getConnection()

getStatement

protected PreparedStatement getStatement()

setStatement

protected void setStatement(PreparedStatement stmt)