Package org.apache.accumulo.core.iterators

Class LongCombiner

java.lang.Object

org.apache.accumulo.core.iterators.WrappingIterator

org.apache.accumulo.core.iterators.Combiner

org.apache.accumulo.core.iterators.TypedValueCombiner<Long>

org.apache.accumulo.core.iterators.LongCombiner

All Implemented Interfaces:

OptionDescriber, SortedKeyValueIterator<Key,Value>, YieldingKeyValueIterator<Key,Value>

Direct Known Subclasses:

MaxCombiner, MinCombiner, SummingCombiner

public abstract class LongCombiner
extends TypedValueCombiner<Long>

A TypedValueCombiner that translates each Value to a Long before reducing, then encodes the reduced Long back to a Value. Subclasses must implement a typedReduce method: public Long typedReduce(Key key, Iterator<Long> iter); This typedReduce method will be passed the most recent Key and an iterator over the Values (translated to Longs) for all non-deleted versions of that Key. A required option for this Combiner is "type" which indicates which type of Encoder to use to encode and decode Longs into Values. Supported types are VARLEN, FIXEDLEN, and STRING which indicate the VarLenEncoder, FixedLenEncoder, and StringEncoder respectively.

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static class	LongCombiner.FixedLenEncoder	An Encoder that uses an 8-byte encoding for Longs.
static class	LongCombiner.StringEncoder	An Encoder that uses a String representation of Longs.
static enum	LongCombiner.Type
static class	LongCombiner.VarLenEncoder	An Encoder that uses a variable-length encoding for Longs.

Nested classes/interfaces inherited from class org.apache.accumulo.core.iterators.Combiner

Combiner.ValueIterator

Nested classes/interfaces inherited from interface org.apache.accumulo.core.iterators.OptionDescriber

OptionDescriber.IteratorOptions

Field Summary

Fields

Modifier and Type	Field	Description
protected static final String	CLASS_PREFIX
static final Encoder<Long>	FIXED_LEN_ENCODER
static final Encoder<Long>	STRING_ENCODER
protected static final String	TYPE
static final Encoder<Long>	VAR_LEN_ENCODER

Fields inherited from class org.apache.accumulo.core.iterators.TypedValueCombiner

LOSSY

Fields inherited from class org.apache.accumulo.core.iterators.Combiner

ALL_OPTION, COLUMNS_OPTION, REDUCE_ON_FULL_COMPACTION_ONLY_OPTION

Constructor Summary

Constructors

Constructor	Description
LongCombiner()

Method Summary

Modifier and Type	Method	Description
OptionDescriber.IteratorOptions	describeOptions()	Gets an iterator options object that contains information needed to configure this iterator.
void	init(SortedKeyValueIterator<Key,Value> source, Map<String,String> options, IteratorEnvironment env)	Initializes the iterator.
static long	safeAdd(long a, long b)
static void	setEncodingType(IteratorSetting is, Class<? extends Encoder<Long>> encoderClass)	A convenience method for setting the long encoding type.
static void	setEncodingType(IteratorSetting is, String encoderClassName)	A convenience method for setting the long encoding type.
static void	setEncodingType(IteratorSetting is, LongCombiner.Type type)	A convenience method for setting the long encoding type.
boolean	validateOptions(Map<String,String> options)	Check to see if an options map contains all options required by an iterator and that the option values are in the expected formats.

Methods inherited from class org.apache.accumulo.core.iterators.TypedValueCombiner

deepCopy, reduce, setEncoder, setEncoder, setLossyness, testEncoder, testEncoder, typedReduce

Methods inherited from class org.apache.accumulo.core.iterators.Combiner

getTopKey, getTopValue, hasTop, next, seek, setColumns, setCombineAllColumns, setReduceOnFullCompactionOnly

Methods inherited from class org.apache.accumulo.core.iterators.WrappingIterator

getSource, isRunningLowOnMemory, setSource

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.apache.accumulo.core.iterators.YieldingKeyValueIterator

enableYielding

Field Details

FIXED_LEN_ENCODER

public static final Encoder<Long> FIXED_LEN_ENCODER

VAR_LEN_ENCODER

public static final Encoder<Long> VAR_LEN_ENCODER

STRING_ENCODER

public static final Encoder<Long> STRING_ENCODER

TYPE

protected static final String TYPE

See Also:

• Constant Field Values

CLASS_PREFIX

protected static final String CLASS_PREFIX

See Also:

• Constant Field Values

Constructor Details

LongCombiner

public LongCombiner()

Method Details

init

public void init(SortedKeyValueIterator<Key,Value> source,
 Map<String,String> options,
 IteratorEnvironment env)
          throws IOException

Description copied from interface: SortedKeyValueIterator

Initializes the iterator. Data should not be read from the source in this method.

Specified by:

init in interface SortedKeyValueIterator<Key,Value>

Overrides:

init in class TypedValueCombiner<Long>

Parameters:

source - SortedKeyValueIterator source to read data from.

options - Map map of string option names to option values.

env - IteratorEnvironment environment in which iterator is being run, provided by Accumulo itself and is expected to be non-null.

Throws:

IOException - unused.

describeOptions

public OptionDescriber.IteratorOptions describeOptions()

Description copied from interface: OptionDescriber

Gets an iterator options object that contains information needed to configure this iterator. This object will be used by the accumulo shell to prompt the user to input the appropriate information.

Specified by:

describeOptions in interface OptionDescriber

Overrides:

describeOptions in class TypedValueCombiner<Long>

Returns:

an iterator options object

validateOptions

public boolean validateOptions(Map<String,String> options)

Description copied from interface: OptionDescriber

Check to see if an options map contains all options required by an iterator and that the option values are in the expected formats.

Specified by:

validateOptions in interface OptionDescriber

Overrides:

validateOptions in class TypedValueCombiner<Long>

Parameters:

options - a map of option names to option values

Returns:

true if options are valid, false otherwise (IllegalArgumentException preferred)

safeAdd

public static long safeAdd(long a,
 long b)

setEncodingType

public static void setEncodingType(IteratorSetting is,
 LongCombiner.Type type)

A convenience method for setting the long encoding type.

Parameters:

is - IteratorSetting object to configure.

type - LongCombiner.Type specifying the encoding type.

setEncodingType

public static void setEncodingType(IteratorSetting is,
 Class<? extends Encoder<Long>> encoderClass)

A convenience method for setting the long encoding type.

Parameters:

is - IteratorSetting object to configure.

encoderClass - Class<? extends Encoder<Long>> specifying the encoding type.

setEncodingType

public static void setEncodingType(IteratorSetting is,
 String encoderClassName)

A convenience method for setting the long encoding type.

Parameters:

is - IteratorSetting object to configure.

encoderClassName - name of a class specifying the encoding type.