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The hash join is an example of a join algorithm and is used in the implementation of a relational database management system.All variants of hash join algorithms involve building hash tables from the tuples of one or both of the joined relations, and subsequently probing those tables so that only tuples with the same hash code need to be compared for equality in equijoins.
Fast-Hash [3] 32 or 64 bits xorshift operations SpookyHash 32, 64, or 128 bits see Jenkins hash function: CityHash [4] 32, 64, 128, or 256 bits FarmHash [5] 32, 64 or 128 bits MetroHash [6] 64 or 128 bits numeric hash (nhash) [7] variable division/modulo xxHash [8] 32, 64 or 128 bits product/rotation t1ha (Fast Positive Hash) [9] 64 or 128 bits ...
As an example, consider the 64-bit FNV-1 hash: All variables, except for byte_of_data, are 64-bit unsigned integers. The variable, byte_of_data, is an 8-bit unsigned integer. The FNV_offset_basis is the 64-bit value: 14695981039346656037 (in hex, 0xcbf29ce484222325). The FNV_prime is the 64-bit value 1099511628211 (in hex, 0x100000001b3).
The meaning of "small enough" depends on the size of the type that is used as the hashed value. For example, in Java, the hash code is a 32-bit integer. Thus the 32-bit integer Integer and 32-bit floating-point Float objects can simply use the value directly, whereas the 64-bit integer Long and 64-bit floating-point Double cannot.
MurmurHash is a non-cryptographic hash function suitable for general hash-based lookup. [1] [2] [3] It was created by Austin Appleby in 2008 [4] and, as of 8 January 2016, [5] is hosted on GitHub along with its test suite named SMHasher.
Algorithm BLAKE2b Input: M Message to be hashed cbMessageLen: Number, (0..2 128) Length of the message in bytes Key Optional 0..64 byte key cbKeyLen: Number, (0..64) Length of optional key in bytes cbHashLen: Number, (1..64) Desired hash length in bytes Output: Hash Hash of cbHashLen bytes Initialize State vector h with IV h 0..7 ← IV 0..7 ...
The algorithm can be described by the following pseudocode, which computes the hash of message C using the permutation table T: algorithm pearson hashing is h := 0 for each c in C loop h := T[ h xor c ] end loop return h The hash variable (h) may be initialized differently, e.g. to the length of the data (C) modulo 256.
The lookup3 function consumes input in 12 byte (96 bit) chunks. [9] It may be appropriate when speed is more important than simplicity. Note, though, that any speed improvement from the use of this hash is only likely to be useful for large keys, and that the increased complexity may also have speed consequences such as preventing an optimizing compiler from inlining the hash function.