Package org.apache.hadoop.mapreduce.lib.db

Class DBInputFormat<T extends DBWritable>

java.lang.Object

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

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

All Implemented Interfaces:

Configurable

Direct Known Subclasses:

DataDrivenDBInputFormat, DBInputFormat

@Public
@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.

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static class	org.apache.hadoop.mapreduce.lib.db.DBInputFormat.DBInputSplit	A InputSplit that spans a set of rows
static class	org.apache.hadoop.mapreduce.lib.db.DBInputFormat.NullDBWritable	A Class that does nothing, implementing DBWritable

Field Summary

Fields

Modifier and Type	Field	Description
protected String	conditions
protected Connection	connection
protected DBConfiguration	dbConf
protected String	dbProductName
protected String[]	fieldNames
protected String	tableName

Constructor Summary

Constructors

Constructor	Description
DBInputFormat()

Method Summary

Modifier and Type	Method	Description
protected void	closeConnection()
Connection	createConnection()
protected RecordReader<LongWritable,T>	createDBRecordReader(org.apache.hadoop.mapreduce.lib.db.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.

Methods inherited from class java.lang.Object

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

Field Details

dbProductName

protected String dbProductName

conditions

protected String conditions

connection

protected Connection connection

tableName

protected String tableName

fieldNames

protected String[] fieldNames

dbConf

protected DBConfiguration dbConf

Constructor Details

DBInputFormat

public DBInputFormat()

Method Details

setConf

public void setConf(Configuration conf)

Set the configuration to be used by this object.

Specified by:

setConf in interface Configurable

Parameters:

conf - configuration to be used

getConf

public Configuration getConf()

Description copied from interface: Configurable

Return the configuration used by this object.

Specified by:

getConf in interface Configurable

Returns:

Configuration

getDBConf

public DBConfiguration getDBConf()

getConnection

public Connection getConnection()

createConnection

public Connection createConnection()

getDBProductName

public String getDBProductName()

createDBRecordReader

protected RecordReader<LongWritable,T> createDBRecordReader(org.apache.hadoop.mapreduce.lib.db.DBInputFormat.DBInputSplit split,
 Configuration conf)
                                                     throws IOException

Throws:

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.

Specified by:

createRecordReader in class InputFormat<LongWritable,T extends DBWritable>

Parameters:

split - the split to be read

context - the information about the task

Returns:

a new record reader

Throws:

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.

Specified by:

getSplits in class InputFormat<LongWritable,T extends DBWritable>

Parameters:

job - job configuration.

Returns:

an array of InputSplits for the job.

Throws:

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.

Parameters:

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

See Also:

• 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.

Parameters:

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"

See Also:

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

closeConnection

protected void closeConnection()