Important Change: If you upgrade to MySQL 4.1.1 or higher, it is difficult to downgrade back to 4.0 or 4.1.0. That is because, for earlier versions,
InnoDBis not aware of multiple tablespaces.
Replication: New binary log format that enables replication of these session variables:
foreign_key_checks(which was replicated since 4.0.14, but here it is done more efficiently and takes less space in the binary logs),
unique_checks. Other variables (like character sets,
sql_select_limit, ...) will be replicated in upcoming 5.0.x releases.
Replication: Easier replication upgrade (5.0.0 masters can read older binary logs and 5.0.0 slaves can read older relay logs). See Replication Compatibility Between MySQL Versions, for more details). The format of the binary log and relay log is changed compared to that of MySQL 4.1 and older.
The output of the
SHOW BINLOG EVENTSstatement has been modified. The
Orig_log_poscolumn has been renamed to
End_log_posand now represents the offset of the last byte of the event, plus one.
KILLstatement now takes
QUERYmodifiers. The first is the same as
KILLwith no modifier (it kills a given connection thread). The second kills only the statement currently being executed by the connection.
For user-defined functions (UDFs), the
UDF_ARGSstructure now has
attribute_lengthsmembers that provide information about the argument names. UDF Argument Processing.
The precedence of the
XORoperator now lies between
XORhad the same precedence as
Basic support for stored procedures and functions (SQL:2003 style). See Using Stored Routines (Procedures and Functions).
LOAD DATA INFILEcauses an implicit commit.
Implemented Index Merge optimization for
ORclauses. See Index Merge Optimization.