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

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

All Implemented Interfaces:

OutputFormat<K,V>

public class DBOutputFormat<K extends DBWritable,V>
extends Object
implements 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

protected class

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

Constructor Summary

DBOutputFormat()

Method Summary

void	checkOutputSpecs(FileSystem filesystem, JobConf job) Check for validity of the output-specification for the job.
protected String	constructQuery(String table, String[] fieldNames) Constructs the query used as the prepared statement to insert data.
RecordWriter<K,V>	getRecordWriter(FileSystem filesystem, JobConf job, String name, Progressable progress) Get the RecordWriter for the given job.
static void	setOutput(JobConf 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

constructQuery

protected 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.

checkOutputSpecs

public void checkOutputSpecs(FileSystem filesystem,
                             JobConf job)
                      throws IOException

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 interface OutputFormat<K extends DBWritable,V>

job - job configuration.

Throws:

IOException - when output should not be attempted

getRecordWriter

public RecordWriter<K,V> getRecordWriter(FileSystem filesystem,
                                         JobConf job,
                                         String name,
                                         Progressable progress)
                                                     throws IOException

Get the RecordWriter for the given job.

Specified by:

getRecordWriter in interface OutputFormat<K extends DBWritable,V>

job - configuration for the job whose output is being written.

name - the unique name for this part of the output.

progress - mechanism for reporting progress while writing to file.

Returns:

a RecordWriter to write the output for the job.

Throws:

IOException

setOutput

public static void setOutput(JobConf job,
                             String tableName,
                             String... fieldNames)

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. If unknown, supply the appropriate number of nulls.