org.apache.hadoop.hbase.mapred

Class GroupingTableMap

java.lang.Object

MapReduceBase

org.apache.hadoop.hbase.mapred.GroupingTableMap

All Implemented Interfaces:

TableMap<ImmutableBytesWritable,Result>

@InterfaceAudience.Public
 @InterfaceStability.Stable
public class GroupingTableMap
extends MapReduceBase
implements TableMap<ImmutableBytesWritable,Result>

Extract grouping columns from input record

Field Summary

Fields

Modifier and Type	Field and Description
protected byte[][]	columns
static 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
GroupingTableMap()

Method Summary

Modifier and Type	Method and Description
void	configure(JobConf job)
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.
static void	initJob(String table, String columns, String groupColumns, Class<? extends TableMap> mapper, JobConf job) Use this before submitting a TableMap job.
void	map(ImmutableBytesWritable key, Result value, <any> output, Reporter reporter) Extract the grouping columns from value to construct a new key.

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 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

Constructor Detail

GroupingTableMap

public GroupingTableMap()

Method Detail

initJob

public static void initJob(String table,
                           String columns,
                           String groupColumns,
                           Class<? extends TableMap> mapper,
                           JobConf job)

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

Parameters:

table - table to be processed

columns - space separated list of columns to fetch

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

mapper - map class

job - job configuration object

configure

public void configure(JobConf job)

map

public void map(ImmutableBytesWritable key,
                Result value,
                <any> output,
                Reporter reporter)
         throws IOException

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 -

value -

output -

reporter -

Throws:

IOException

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 -

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 -

Returns:

key generated by concatenating multiple column values