Package org.hibernate.search.util.common.data.impl

Class RangeHashTable<T>

java.lang.Object

org.hibernate.search.util.common.data.impl.HashTable<T>

org.hibernate.search.util.common.data.impl.RangeHashTable<T>

Type Parameters:

T - The type of elements stored in each bucket.

All Implemented Interfaces:

Iterable<T>

public final class RangeHashTable<T>
extends HashTable<T>

A hash table that derives an index from hashes using a partition of the hashing space based on contiguous ranges.

This makes this table particularly suitable in situations where the hash must be computed before the number of buckets is known, then stored, then queried efficiently (e.g. retrieve all entries for a given bucket by querying WHERE hash BETWEEN bucketLowerBound AND bucketUpperBound). This wouldn't be as efficient with a modulo-based hash table such as ModuloHashTable, since the modulo operation would have to be applied to all entries at query time (it cannot be indexed since the number of buckets is not known when hashing).

Constructor Summary

Constructors

Constructor	Description
RangeHashTable(RangeCompatibleHashFunction hashFunction, int size)

Method Summary

Modifier and Type	Method	Description
int	computeIndex(CharSequence key)	Hashes a key and computes an array index based on that hash.
int	computeIndexForHash(int hash)
Range<Integer>	rangeForBucket(int index)

Methods inherited from class org.hibernate.search.util.common.data.impl.HashTable

get, get, iterator, set, size

Methods inherited from class java.lang.Object

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

Methods inherited from interface java.lang.Iterable

forEach, spliterator

Constructor Detail

RangeHashTable

public RangeHashTable(RangeCompatibleHashFunction hashFunction,
                      int size)

Method Detail

computeIndex

public int computeIndex(CharSequence key)

Description copied from class: HashTable

Hashes a key and computes an array index based on that hash.

The maximum index is defined by constructor parameters passed to the hash function.

Specified by:

computeIndex in class HashTable<T>

Parameters:

key - A key to hash in order to compute an index.

Returns:

The index to use for the given key in a hash table of size size.

computeIndexForHash

public int computeIndexForHash(int hash)

rangeForBucket

public Range<Integer> rangeForBucket(int index)

Parameters:

index - An index between 0 and HashTable.size() (exclusive).

Returns:

The range of hashes associated to the bucket for that index.