org.apache.hadoop.mapred.lib.db

类 DBOutputFormat<K extends DBWritable,V>

java.lang.Object

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

所有已实现的接口:

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 RecordWriter writes only the key to the database with a batch SQL query.

嵌套类概要

嵌套类

限定符和类型	类和说明
protected class	DBOutputFormat.DBRecordWriter A RecordWriter that writes the reduce output to a SQL table

构造器概要

构造器

构造器和说明
DBOutputFormat()

方法概要

方法

限定符和类型	方法和说明
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

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

DBOutputFormat

public DBOutputFormat()

方法详细资料

constructQuery

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

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

参数:

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.

指定者:

checkOutputSpecs 在接口中 OutputFormat<K extends DBWritable,V>

job - job configuration.

抛出:

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.

指定者:

getRecordWriter 在接口中 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.

返回:

a RecordWriter to write the output for the job.

抛出:

IOException

setOutput

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

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

参数:

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.