Bug#16377: Wrong DATE/DATETIME comparison in BETWEEN function.

The BETWEEN function was comparing DATE/DATETIME values either as ints or as
strings. Both methods have their disadvantages and may lead to a wrong
result.

Now BETWEEN function checks whether all of its arguments has the STRING result
types and at least one of them is a DATE/DATETIME item. If so it sets up
two Arg_comparator obects to compare with the compare_datetime() comparator
and uses them to compare such items.

Added two Arg_comparator object members and one flag to the
Item_func_between class for the correct DATE/DATETIME comparison.
The Item_func_between::fix_length_and_dec() function now detects whether
it's used for DATE/DATETIME comparison and sets up newly added Arg_comparator
objects to do this.
The Item_func_between::val_int() now uses Arg_comparator objects to perform
correct DATE/DATETIME comparison.
The owner variable of the Arg_comparator class now can be set to NULL if the
caller wants to handle NULL values by itself.
Now the Item_date_add_interval::get_date() function ajusts cached_field type according to the detected type.


mysql-test/t/type_datetime.test:
  Added a test case for the bug#16377: Wrong DATE/DATETIME comparison in BETWEEN function.
mysql-test/r/type_datetime.result:
  Added a test case for the bug#16377: Wrong DATE/DATETIME comparison in BETWEEN function.
mysql-test/r/query_cache.result:
  A test case result corrected after the fix for bug#16377.
sql/item_timefunc.cc:
  Bug#16377: Wrong DATE/DATETIME comparison in BETWEEN function.
  Now the Item_date_add_interval::get_date() function ajusts cached_field type according to the detected type.
sql/item_cmpfunc.cc:
  Bug#16377: Wrong DATE/DATETIME comparison in BETWEEN function.
  The Item_func_between::fix_length_and_dec() function now detects whether
  it's used for DATE/DATETIME comparison and sets up newly added Arg_comparator
  objects to do this.
  The Item_func_between::val_int() now uses Arg_comparators to perform correct
  DATE/DATETIME comparison.
  The owner variable of the Arg_comparator class now can be set to NULL if the
  caller wants to handle NULL values by itself.
sql/item_cmpfunc.h:
  Bug#16377: Wrong DATE/DATETIME comparison in BETWEEN function.
  Added two Arg_comparator object members and one flag
  to the Item_func_between class for the correct DATE/DATETIME comparison.

1 files changed, 6 insertions, 1 deletions

diff --git a/sql/item_cmpfunc.h b/sql/item_cmpfunc.h
index 6318c7444de..761ca90d0a7 100644
--- a/sql/item_cmpfunc.h
+++ b/sql/item_cmpfunc.h
@@ -91,6 +91,7 @@ public:
   static enum enum_date_cmp_type can_compare_as_dates(Item *a, Item *b,
                                                       ulonglong *const_val_arg);
 
+  void set_datetime_cmp_func(Item **a1, Item **b1);
   static arg_cmp_func comparator_matrix [5][2];
 
   friend class Item_func;
@@ -579,8 +580,12 @@ class Item_func_between :public Item_func_opt_neg
 public:
   Item_result cmp_type;
   String value0,value1,value2;
+  /* TRUE <=> arguments will be compared as dates. */
+  bool compare_as_dates;
+  /* Comparators used for DATE/DATETIME comparison. */
+  Arg_comparator ge_cmp, le_cmp;
   Item_func_between(Item *a, Item *b, Item *c)
-    :Item_func_opt_neg(a, b, c) {}
+    :Item_func_opt_neg(a, b, c), compare_as_dates(FALSE) {}
   longlong val_int();
   optimize_type select_optimize() const { return OPTIMIZE_KEY; }
   enum Functype functype() const   { return BETWEEN; }