A deep look at MySQL 5.5 partitioning enhancements
December 28, 2009[From MySQL AB]
The release of MySQL 5.5 has brought several enhancements. While most of the coverage went, understandably, to the semi-synchronous replication, the enhancements of partitioning were neglected, and sometimes there was some degree of misunderstanding on their true meaning. With this article, we want to explain these cool enhancements, especially the parts that were not fully understood.
Anyone who has used partitions so far (see MySQL 5.1 partitions in practice) has experienced some frustration at the amount of problems to face when using non-integer columns. Partitions in 5.1 can only deal with integer values, meaning that if you want to do partitions on dates or strings, you had to convert these columns with a function.
The article continues at http://dev.mysql.com/tech-resources/articles/mysql_55_partitioning.html