Class LongCombiner
- java.lang.Object
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- org.apache.accumulo.core.iterators.WrappingIterator
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- org.apache.accumulo.core.iterators.Combiner
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- org.apache.accumulo.core.iterators.TypedValueCombiner<Long>
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- org.apache.accumulo.core.iterators.LongCombiner
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- 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 VARNUM, LONG, and STRING which indicate the VarNumEncoder, LongEncoder, and StringEncoder respectively.
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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 class
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
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Nested classes/interfaces inherited from interface org.apache.accumulo.core.iterators.OptionDescriber
OptionDescriber.IteratorOptions
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Field Summary
Fields Modifier and Type Field Description protected static String
CLASS_PREFIX
static Encoder<Long>
FIXED_LEN_ENCODER
static Encoder<Long>
STRING_ENCODER
protected static String
TYPE
static Encoder<Long>
VAR_LEN_ENCODER
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Fields inherited from class org.apache.accumulo.core.iterators.TypedValueCombiner
LOSSY
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Fields inherited from class org.apache.accumulo.core.iterators.Combiner
ALL_OPTION, COLUMNS_OPTION, REDUCE_ON_FULL_COMPACTION_ONLY_OPTION
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Constructor Summary
Constructors Constructor Description LongCombiner()
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Method Summary
All Methods Static Methods Instance Methods Concrete Methods 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
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Methods inherited from class org.apache.accumulo.core.iterators.Combiner
getTopKey, getTopValue, hasTop, next, seek, setColumns, setCombineAllColumns, setReduceOnFullCompactionOnly
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Methods inherited from class org.apache.accumulo.core.iterators.WrappingIterator
getSource, setSource
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Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
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Methods inherited from interface org.apache.accumulo.core.iterators.YieldingKeyValueIterator
enableYielding
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Field Detail
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TYPE
protected static final String TYPE
- See Also:
- Constant Field Values
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CLASS_PREFIX
protected static final String CLASS_PREFIX
- See Also:
- Constant Field Values
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Method Detail
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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 interfaceSortedKeyValueIterator<Key,Value>
- Overrides:
init
in classTypedValueCombiner<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.- Throws:
IOException
- unused.
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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 interfaceOptionDescriber
- Overrides:
describeOptions
in classTypedValueCombiner<Long>
- Returns:
- an iterator options object
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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 interfaceOptionDescriber
- Overrides:
validateOptions
in classTypedValueCombiner<Long>
- Parameters:
options
- a map of option names to option values- Returns:
- true if options are valid, false otherwise (IllegalArgumentException preferred)
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safeAdd
public static long safeAdd(long a, long b)
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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.
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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.
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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.
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