Package io.prestosql.operator.aggregation

Class VarcharApproximateMostFrequent

java.lang.Object

io.prestosql.operator.aggregation.VarcharApproximateMostFrequent

public final class VarcharApproximateMostFrequent
extends Object

Aggregation function that approximates the frequency of the top-K elements. This function keeps counts for a "frequent" subset of elements and assumes all other elements once fewer than the least-frequent "frequent" element.

The algorithm is based loosely on: Efficient Computation of Frequent and Top-*k* Elements in Data Streams by Ahmed Metwally, Divyakant Agrawal, and Amr El Abbadi

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static interface	VarcharApproximateMostFrequent.State

Method Summary

Modifier and Type	Method	Description
static void	combine(VarcharApproximateMostFrequent.State state, VarcharApproximateMostFrequent.State otherState)
static void	input(VarcharApproximateMostFrequent.State state, long buckets, io.airlift.slice.Slice value, long capacity)
static void	output(VarcharApproximateMostFrequent.State state, BlockBuilder out)

Methods inherited from class java.lang.Object

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

Method Detail

input

public static void input(VarcharApproximateMostFrequent.State state,
                         long buckets,
                         io.airlift.slice.Slice value,
                         long capacity)

combine

public static void combine(VarcharApproximateMostFrequent.State state,
                           VarcharApproximateMostFrequent.State otherState)

output

public static void output(VarcharApproximateMostFrequent.State state,
                          BlockBuilder out)