The mysqlnd replication and load balancing plugin (mysqlnd_ms) adds easy to use MySQL replication support to all PHP MySQL extensions that use mysqlnd.
Today a customer mentioned reordering a MyISAM table to get rid of fragmentation. I asked them to clarify what they meant by reordering, assuming that they were running an OPTIMIZE or a NULL ALTER TABLE operation and they said that they use ALTER TABLE t1 ORDER BY f1, f2, f3,..etc;
In a SQL server, the data tables sit on disk. Indexes provide a means for the server to find a particular row of data in the table without having to search the entire table. When the entire table has to be searched, it's called a table scan. Most often, you want only a small subset of the data in the table, so a full table scan wastes a lot of disk I/O and therefore time.This problem is compounded when data must be joined, because many more rows must be compared between the two sides of the join.