The following performance issues are specific to or especially pronounced in MySQL Cluster:
There are query performance issues due to sequential
access to the
engine; it is also relatively more expensive to do many
range scans than it is with either
Records in range.
Records in range statistic is
available but is not completely tested or officially
supported. This may result in nonoptimal query plans in
some cases. If necessary, you can employ
FORCE INDEX to alter
the execution plan. See Index Hint Syntax, for
more information on how to do this.
Unique hash indexes.
Unique hash indexes created with
HASH cannot be used for accessing a table if
NULL is given as part of the key.