from 5.1 to 5.5

(Former 59405)

In this bug, args[0] in an Item_func_find_in_set stored an 
Item_func_weekday that was constant. In 
Item_func_find_in_set::fix_length_and_dec(), args[0]->val_str() 
was called. Later, when Item_func_find_in_set::val_int() was 
called, args[0]->null_value was checked. However, the 
Item_func_weekday in args[0] had now been replaced with an 
Item_cache. No val_*() calls had been made to this Item_cache,
thus null_value was incorrectly 'true', resulting in missing 
rows in the result set.

enum_value gets a value in fix_length_and_dec() iff args[0]
is both constant and non-null. It is therefore unnecessary 
to check the null_value of args[0] in val_int().

An alternative fix would be to call args[0]->val_int() inside 
Item_func_find_in_set::val_int(). This would ensure
args[0]->null_value was set correctly (always false in this case), 
but that would have to be done for every record this const value 
is checked against.


mysql-test/r/func_set.result:
  Add test for BUG#59405
mysql-test/t/func_set.test:
  Add test for BUG#59405