Fixed a bug: the InnoDB range estimator greatly exaggerated
the size of a short index range if the paths to the endpoints of
the range in the index tree happened to branch already in the root.
This could cause unnecessary table scans in SQL queries.
Fixed a bug: ORDER BY could fail if you had not created a
primary key to a table, but had defined several indexes
of which at least one was a UNIQUE index with all its
columns declared as NOT NULL.
Fixed a bug: a lock wait timeout in connection with
ON DELETE CASCADE could cause corruption in indexes.
Fixed a bug: if a SELECT was done with a unique key
from a primary index, and the search matched to a
delete-marked record, InnoDB could erroneously return the NEXT record.
Fixed a bug introduced in 3.23.53: LOCK TABLES ... READ LOCAL
should not set row locks on the rows read. This caused deadlocks
and lock wait timeouts in mysqldump.
Fixed a bug: if an index contains some column twice, and that
column is updated, the table will become corrupt. From now on
InnoDB prevents creation of such indexes.