Can somebody help me understand the use and benefits of these three functions that Percona suggests right after installation?
* Percona XtraDB Cluster is distributed with several useful UDF (User Defined Function) from Percona Toolkit.
* Run the following commands to create these functions:
mysql -e "CREATE FUNCTION fnv1a_64 RETURNS INTEGER SONAME 'libfnv1a_udf.so'"
mysql -e "CREATE FUNCTION fnv_64 RETURNS INTEGER SONAME 'libfnv_udf.so'"
mysql -e "CREATE FUNCTION murmur_hash RETURNS INTEGER SONAME 'libmurmur_udf.so'"
* See http://www.percona.com/doc/percona-server/5.7/management/udf_percona_toolkit.html for more details
I have never been able to find documentation that clearly explains these function, and what benefits/advantages you get from them.
The benefit of these functions are "faster checksums"...i.e. more efficient implementations of a couple of hash functions.
But that's only a benefit if you have a need (requirement) generate values provided by these hash functions.
If you don't have any need to generate hash values, then these functions don't provide any benefit.
References:
http://en.wikipedia.org/wiki/Fowler%E2%80%93Noll%E2%80%93Vo_hash_function