> ------------------------------------------------------------
> revno: 3452.13.54
> revision-id: oystein.grovlen@oracle.com-20110112093715-tc076voaxwblqk8v
> parent: georgi.kodinov@oracle.com-20110110130833-1c9q21mr7zoq07vg
> committer: Oystein Grovlen <oystein.grovlen@oracle.com>
> branch nick: mysql-5.1-security
> timestamp: Wed 2011-01-12 10:37:15 +0100
> message:
>   Bug#59211: Select Returns Different Value for min(year) Function
>   
>   get_year_value() contains code to convert 2-digits year to
>   4-digits.  The fix for Bug#49910 added a check on the size of
>   the underlying field so that this conversion is not done for
>   YEAR(4) values. (Since otherwise one would convert invalid
>   YEAR(4) values to valid ones.)
>   
>   The existing check does not work when Item_cache is used, since
>   it is not detected when the cache is based on a Field.  The
>   reported change in behavior is due to Bug#58030 which added
>   extra cached items in min/max computations.
>   
>   The elegant solution would be to implement
>   Item_cache::real_item() to return the underlying Item.
>   However, some side effects are observed (change in explain
>   output) that indicates that such a change is not straight-
>   forward, and definitely not appropriate for an MRU.
>   
>   Instead, a Item_cache::field() method has been added in order
>   to get access to the underlying field.  (This field() method
>   eliminates the need for Item_cache::eq_def() used in
>   test_if_ref(), but in order to limit the scope of this fix,
>   that code has been left as is.)