Functionality added or changed:
OPTIMIZE TABLE
will for MyISAM tables
treat all NULL
values as different when
calculating cardinality. This helps in optimising joins
between tables where one of the tables has a lot of
NULL
values in a indexed column:
SELECT * from t1,t2 where t1.a=t2.key_with_a_lot_of_null;
Added join operator FORCE INDEX
(key_list)
. This acts likes USE INDEX
(key_list)
but with the addition that a table scan
is assumed to be VERY expensive. One bad thing with this is
that it makes FORCE
a reserved word.
Reset internal row buffer in MyISAM after each query. This will reduce memory in the case you have a lot of big blobs in a table.
Bugs fixed:
A security patch in 4.0.8 causes the mysqld server to die if the remote hostname can't be resolved. This is now fixed.
Fixed crash when replication big LOAD DATA
INFILE
statement that caused log rotation.
This is a translation of the MySQL Reference Manual that can be found at dev.mysql.com. The original Reference Manual is in English, and this translation is not necessarily as up to date as the English version.