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Functionality added or changed:
OPTIMIZE TABLE for
MyISAM tables treats all
NULL values as different when calculating
cardinality. This helps in optimizing joins between tables
where one of the tables has a lot of
values in a indexed column:
SELECT * from t1, t2 where t1.a=t2.key_with_a_lot_of_null;
Added join operator
(index_list). This acts likes
(index_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
each query. This reduces memory in case you have a lot of big
blobs in a table.