Indexes are separate data structures that provide alternate
pathways to finding data. They can and do generally speed up the
processing of queries and other DML commands, like the
DELETE statements. Indexes are also
called fast access paths.
In the scope of the InnoDB Database Engine, the MySQL database
maintains the integrity of indexes after you create them. The
upside of indexes is that they can improve SQL statement
performance. The downside is that they impose overhead on every
DELETE statement, because the
database maintains them by inserting, updating, or deleting items
for each related change in the tables that the indexes support.
Indexes have two key properties—usability and visibility. Indexes
are both usable and visible by default. That means they …[Read more]