org.apache.hadoop.hbase.mapreduce

Class GroupingTableMapper

java.lang.Object

<any>

org.apache.hadoop.hbase.mapreduce.TableMapper<ImmutableBytesWritable,Result>

org.apache.hadoop.hbase.mapreduce.GroupingTableMapper

@InterfaceAudience.Public
 @InterfaceStability.Stable
public class GroupingTableMapper
extends TableMapper<ImmutableBytesWritable,Result>

Extract grouping columns from input record.

Field Summary

Fields

Modifier and Type	Field and Description
protected byte[][]	columns The grouping columns.
static java.lang.String	GROUP_COLUMNS JobConf parameter to specify the columns used to produce the key passed to collect from the map phase.

Constructor Summary

Constructors

Constructor and Description
GroupingTableMapper()

Method Summary

Modifier and Type	Method and Description
protected ImmutableBytesWritable	createGroupKey(byte[][] vals) Create a key by concatenating multiple column values.
protected byte[][]	extractKeyValues(Result r) Extract columns values from the current record.
Configuration	getConf() Returns the current configuration.
static void	initJob(java.lang.String table, Scan scan, java.lang.String groupColumns, java.lang.Class<? extends TableMapper> mapper, Job job) Use this before submitting a TableMap job.
void	map(ImmutableBytesWritable key, Result value, Context context) Extract the grouping columns from value to construct a new key.
void	setConf(Configuration configuration) Sets the configuration.

Methods inherited from class java.lang.Object

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

Field Detail

GROUP_COLUMNS

public static final java.lang.String GROUP_COLUMNS

JobConf parameter to specify the columns used to produce the key passed to collect from the map phase.

See Also:

Constant Field Values

columns

protected byte[][] columns

The grouping columns.

Constructor Detail

GroupingTableMapper

public GroupingTableMapper()

Method Detail

initJob

public static void initJob(java.lang.String table,
                           Scan scan,
                           java.lang.String groupColumns,
                           java.lang.Class<? extends TableMapper> mapper,
                           Job job)
                    throws java.io.IOException

Use this before submitting a TableMap job. It will appropriately set up the job.

Parameters:

table - The table to be processed.

scan - The scan with the columns etc.

groupColumns - A space separated list of columns used to form the key used in collect.

mapper - The mapper class.

job - The current job.

Throws:

java.io.IOException - When setting up the job fails.

map

public void map(ImmutableBytesWritable key,
                Result value,
                Context context)
         throws java.io.IOException,
                java.lang.InterruptedException

Extract the grouping columns from value to construct a new key. Pass the new key and value to reduce. If any of the grouping columns are not found in the value, the record is skipped.

Parameters:

key - The current key.

value - The current value.

context - The current context.

Throws:

java.io.IOException - When writing the record fails.

java.lang.InterruptedException - When the job is aborted.

extractKeyValues

protected byte[][] extractKeyValues(Result r)

Extract columns values from the current record. This method returns null if any of the columns are not found.

Override this method if you want to deal with nulls differently.

Parameters:

r - The current values.

Returns:

Array of byte values.

createGroupKey

protected ImmutableBytesWritable createGroupKey(byte[][] vals)

Create a key by concatenating multiple column values.

Override this function in order to produce different types of keys.

Parameters:

vals - The current key/values.

Returns:

A key generated by concatenating multiple column values.

getConf

public Configuration getConf()

Returns the current configuration.

Returns:

The current configuration.

See Also:

org.apache.hadoop.conf.Configurable#getConf()

setConf

public void setConf(Configuration configuration)

Sets the configuration. This is used to set up the grouping details.

Parameters:

configuration - The configuration to set.

See Also:

org.apache.hadoop.conf.Configurable#setConf( org.apache.hadoop.conf.Configuration)