org.apache.hadoop.mapreduce.lib.db

类 DBInputFormat<T extends DBWritable>

java.lang.Object

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

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

所有已实现的接口:

Configurable

直接已知子类:

DataDrivenDBInputFormat

@InterfaceAudience.Public
@InterfaceStability.Stable
public class DBInputFormat<T extends DBWritable>
extends InputFormat<LongWritable,T>
implements Configurable

A InputFormat that reads input data from an SQL table.

DBInputFormat emits LongWritables containing the record number as key and DBWritables as value. The SQL query, and input class can be using one of the two setInput methods.

嵌套类概要

嵌套类

限定符和类型	类和说明
static class	DBInputFormat.DBInputSplit A InputSplit that spans a set of rows
static class	DBInputFormat.NullDBWritable A Class that does nothing, implementing DBWritable

构造器概要

构造器

构造器和说明
DBInputFormat()

方法概要

方法

限定符和类型	方法和说明
protected void	closeConnection()
protected RecordReader<LongWritable,T>	createDBRecordReader(DBInputFormat.DBInputSplit split, Configuration conf)
RecordReader<LongWritable,T>	createRecordReader(InputSplit split, TaskAttemptContext context) Create a record reader for a given split.
Configuration	getConf() Return the configuration used by this object.
Connection	getConnection()
protected String	getCountQuery() Returns the query for getting the total number of rows, subclasses can override this for custom behaviour.
DBConfiguration	getDBConf()
String	getDBProductName()
List<InputSplit>	getSplits(JobContext job) Logically split the set of input files for the job.
void	setConf(Configuration conf) Set the configuration to be used by this object.
static void	setInput(Job job, Class<? extends DBWritable> inputClass, String inputQuery, String inputCountQuery) Initializes the map-part of the job with the appropriate input settings.
static void	setInput(Job job, Class<? extends DBWritable> inputClass, String tableName, String conditions, String orderBy, String... fieldNames) Initializes the map-part of the job with the appropriate input settings.

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

public DBInputFormat()

方法详细资料

setConf

public void setConf(Configuration conf)

Set the configuration to be used by this object.

指定者:

setConf 在接口中 Configurable

getConf

public Configuration getConf()

从接口复制的说明: Configurable

Return the configuration used by this object.

指定者:

getConf 在接口中 Configurable

getDBConf

public DBConfiguration getDBConf()

getConnection

public Connection getConnection()

getDBProductName

public String getDBProductName()

createDBRecordReader

protected RecordReader<LongWritable,T> createDBRecordReader(DBInputFormat.DBInputSplit split,
                                                Configuration conf)
                                                                        throws IOException

抛出:

IOException

createRecordReader

public RecordReader<LongWritable,T> createRecordReader(InputSplit split,
                                              TaskAttemptContext context)
                                                                   throws IOException,
                                                                          InterruptedException

Create a record reader for a given split. The framework will call RecordReader.initialize(InputSplit, TaskAttemptContext) before the split is used.

指定者:

createRecordReader 在类中 InputFormat<LongWritable,T extends DBWritable>

参数:

split - the split to be read

context - the information about the task

返回:

a new record reader

抛出:

IOException

InterruptedException

getSplits

public List<InputSplit> getSplits(JobContext job)
                           throws IOException

Logically split the set of input files for the job.

Each InputSplit is then assigned to an individual Mapper for processing.

Note: The split is a logical split of the inputs and the input files are not physically split into chunks. For e.g. a split could be <input-file-path, start, offset> tuple. The InputFormat also creates the RecordReader to read the InputSplit.

指定者:

getSplits 在类中 InputFormat<LongWritable,T extends DBWritable>

参数:

job - job configuration.

返回:

an array of InputSplits for the job.

抛出:

IOException

getCountQuery

protected String getCountQuery()

Returns the query for getting the total number of rows, subclasses can override this for custom behaviour.

setInput

public static void setInput(Job job,
            Class<? extends DBWritable> inputClass,
            String tableName,
            String conditions,
            String orderBy,
            String... fieldNames)

Initializes the map-part of the job with the appropriate input settings.

参数:

job - The map-reduce job

inputClass - the class object implementing DBWritable, which is the Java object holding tuple fields.

tableName - The table to read data from

conditions - The condition which to select data with, eg. '(updated > 20070101 AND length > 0)'

orderBy - the fieldNames in the orderBy clause.

fieldNames - The field names in the table

另请参阅:

setInput(Job, Class, String, String)

setInput

public static void setInput(Job job,
            Class<? extends DBWritable> inputClass,
            String inputQuery,
            String inputCountQuery)

Initializes the map-part of the job with the appropriate input settings.

参数:

job - The map-reduce job

inputClass - the class object implementing DBWritable, which is the Java object holding tuple fields.

inputQuery - the input query to select fields. Example : "SELECT f1, f2, f3 FROM Mytable ORDER BY f1"

inputCountQuery - the input query that returns the number of records in the table. Example : "SELECT COUNT(f1) FROM Mytable"

另请参阅:

setInput(Job, Class, String, String, String, String...)

closeConnection

protected void closeConnection()