Package io.prestosql.operator.aggregation

Class ApproximateMostFrequentHistogram<K>

java.lang.Object

io.prestosql.operator.aggregation.ApproximateMostFrequentHistogram<K>

Type Parameters:

K -

public class ApproximateMostFrequentHistogram<K>
extends Object

Calculate the histogram approximately for topk elements based on the Space-Saving algorithm and the Stream-Summary data structure as described in: Efficient Computation of Frequent and Top-k Elements in Data Streams by Metwally, Agrawal, and Abbadi

Constructor Summary

Constructors

Constructor	Description
ApproximateMostFrequentHistogram(int maxBuckets, int capacity, ApproximateMostFrequentBucketSerializer<K> serializer, ApproximateMostFrequentBucketDeserializer<K> deserializer)
ApproximateMostFrequentHistogram(io.airlift.slice.Slice serialized, ApproximateMostFrequentBucketSerializer<K> serializer, ApproximateMostFrequentBucketDeserializer<K> deserializer)

Method Summary

Modifier and Type	Method	Description
void	add(K value)
void	add(K value, long incrementCount)
long	estimatedInMemorySize()
void	forEachBucket(BucketConsumer<K> consumer)
Map<K,Long>	getBuckets()
void	merge(ApproximateMostFrequentHistogram<K> other)
io.airlift.slice.Slice	serialize()

Methods inherited from class java.lang.Object

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

Constructor Detail

ApproximateMostFrequentHistogram

public ApproximateMostFrequentHistogram(int maxBuckets,
                                        int capacity,
                                        ApproximateMostFrequentBucketSerializer<K> serializer,
                                        ApproximateMostFrequentBucketDeserializer<K> deserializer)

Parameters:

maxBuckets - The maximum number of elements stored in the bucket.

capacity - The maximum capacity of the stream summary data structure.

serializer - It serializes a bucket into varbinary slice.

deserializer - It appends a bucket into the histogram.

ApproximateMostFrequentHistogram

public ApproximateMostFrequentHistogram(io.airlift.slice.Slice serialized,
                                        ApproximateMostFrequentBucketSerializer<K> serializer,
                                        ApproximateMostFrequentBucketDeserializer<K> deserializer)

Method Detail

add

public void add(K value)

add

public void add(K value,
                long incrementCount)

serialize

public io.airlift.slice.Slice serialize()

merge

public void merge(ApproximateMostFrequentHistogram<K> other)

forEachBucket

public void forEachBucket(BucketConsumer<K> consumer)

getBuckets

public Map<K,Long> getBuckets()

estimatedInMemorySize

public long estimatedInMemorySize()