org.apache.hadoop.mapreduce.lib.db
Class DBOutputFormat<K extends DBWritable,V>

java.lang.Object
  org.apache.hadoop.mapreduce.OutputFormat<K,V>
      org.apache.hadoop.mapreduce.lib.db.DBOutputFormat<K,V>

@InterfaceAudience.Public
@InterfaceStability.Stable
public class DBOutputFormat<K extends DBWritable,V>
extends OutputFormat<K,V>

A OutputFormat that sends the reduce output to a SQL table.

DBOutputFormat accepts <key,value> pairs, where key has a type extending DBWritable. Returned DBOutputFormat.DBRecordWriter writes only the key to the database with a batch SQL query.

Nested Class Summary

class

DBOutputFormat.DBRecordWriter A RecordWriter that writes the reduce output to a SQL table

Constructor Summary

DBOutputFormat()

Method Summary

void	checkOutputSpecs(JobContext context) Check for validity of the output-specification for the job.
String	constructQuery(String table, String[] fieldNames) Constructs the query used as the prepared statement to insert data.
OutputCommitter	getOutputCommitter(TaskAttemptContext context) Get the output committer for this output format.
RecordWriter<K,V>	getRecordWriter(TaskAttemptContext context) Get the RecordWriter for the given task.
static void	setOutput(Job job, String tableName, int fieldCount) Initializes the reduce-part of the job with the appropriate output settings
static void	setOutput(Job job, String tableName, String... fieldNames) Initializes the reduce-part of the job with the appropriate output settings

Methods inherited from class java.lang.Object

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

Constructor Detail

DBOutputFormat

public DBOutputFormat()

Method Detail

checkOutputSpecs

public void checkOutputSpecs(JobContext context)
                      throws IOException,
                             InterruptedException

Description copied from class: OutputFormat

Check for validity of the output-specification for the job.

This is to validate the output specification for the job when it is a job is submitted. Typically checks that it does not already exist, throwing an exception when it already exists, so that output is not overwritten.

Specified by:

checkOutputSpecs in class OutputFormat<K extends DBWritable,V>

Parameters:

context - information about the job

Throws:

IOException - when output should not be attempted

InterruptedException

getOutputCommitter

public OutputCommitter getOutputCommitter(TaskAttemptContext context)
                                   throws IOException,
                                          InterruptedException

Description copied from class: OutputFormat

Get the output committer for this output format. This is responsible for ensuring the output is committed correctly.

Specified by:

getOutputCommitter in class OutputFormat<K extends DBWritable,V>

Parameters:

context - the task context

Returns:

an output committer

Throws:

IOException

InterruptedException

constructQuery

public String constructQuery(String table,
                             String[] fieldNames)

Constructs the query used as the prepared statement to insert data.

Parameters:

table - the table to insert into

fieldNames - the fields to insert into. If field names are unknown, supply an array of nulls.

getRecordWriter

public RecordWriter<K,V> getRecordWriter(TaskAttemptContext context)
                                                     throws IOException

Get the RecordWriter for the given task.

Specified by:

getRecordWriter in class OutputFormat<K extends DBWritable,V>

Parameters:

context - the information about the current task.

Returns:

a RecordWriter to write the output for the job.

Throws:

IOException

setOutput

public static void setOutput(Job job,
                             String tableName,
                             String... fieldNames)
                      throws IOException

Initializes the reduce-part of the job with the appropriate output settings

Parameters:

job - The job

tableName - The table to insert data into

fieldNames - The field names in the table.

Throws:

IOException

setOutput

public static void setOutput(Job job,
                             String tableName,
                             int fieldCount)
                      throws IOException

Initializes the reduce-part of the job with the appropriate output settings

Parameters:

job - The job

tableName - The table to insert data into

fieldCount - the number of fields in the table.

Throws:

IOException