Fixed bug#16377: result of DATE/TIME functions were compared as strings which

can lead to a wrong result.

All date/time functions has the STRING result type thus their results are
compared as strings. The string date representation allows a user to skip 
some of leading zeros. This can lead to wrong comparison result if a date/time 
function result is compared to such a string constant.

The idea behind this bug fix is to compare results of date/time functions
and data/time constants as ints, because that date/time representation is 
more exact. To achieve this the agg_cmp_type() is changed to take in the
account that a date/time field or an date/time item should be compared 
as ints.

This bug fix is partially back ported from 5.0.

The agg_cmp_type() function now accepts THD as one of parameters. 
In addition, it now checks if a date/time field/function is present in the
list. If so, it tries to coerce all constants to INT to make date/time
comparison return correct result. The field for the constant coercion is
taken from the Item_field or constructed from the Item_func. In latter case
the constructed field will be freed after conversion of all constant items.
Otherwise the result is same as before - aggregated with help of the
item_cmp_type() function.

From the Item_func_between::fix_length_and_dec() function removed the part
which was converting date/time constants to int if possible. Now this is 
done by the agg_cmp_type() function.

The new function result_as_longlong() is added to the Item class. 
It indicates that the item is a date/time item and result of it can be
compared as int. Such items are date/time fields/functions.

Correct val_int() methods are implemented for classes Item_date_typecast, 
Item_func_makedate, Item_time_typecast, Item_datetime_typecast. All these
classes are derived from Item_str_func and Item_str_func::val_int() converts
its string value to int without regard to the date/time type of these items.

Arg_comparator::set_compare_func() and Arg_comparator::set_cmp_func()
functions are changed to substitute result type of an item with the INT_RESULT
if the item is a date/time item and another item is a constant. This is done
to get a correct result of comparisons like date_time_function() = string_constant.


mysql-test/r/cast.result:
  Fixed wrong test case result after bug fix#16377.
sql/item_timefunc.h:
  Fixed bug#16377: result of DATE/TIME functions were compared as strings which
  can lead to a wrong result.
  The result_as_longlong() function is set to return TRUE for these classes:
  Item_date, Item_date_func, Item_func_curtime, Item_func_sec_to_time,
  Item_date_typecast, Item_time_typecast, Item_datetime_typecast,
  Item_func_makedate.
sql/item_timefunc.cc:
  Fixed bug#16377: result of DATE/TIME functions were compared as strings which
  can lead to a wrong result.Correct val_int() methods are implemented for classes Item_date_typecast, 
  Item_func_makedate, Item_time_typecast, Item_datetime_typecast.
sql/item_cmpfunc.h:
  Fixed bug#16377: result of DATE/TIME functions were compared as strings which
  can lead to a wrong result.
  Arg_comparator::set_compare_func() and Arg_comparator::set_cmp_func()
  functions are changed to substitute result type of an item with the INT_RESULT
  if the item is a date/time item and another item is a constant.
sql/field.cc:
  Fixed bug#16377: result of DATE/TIME functions were compared as strings which
  can lead to a wrong result.
  Field::set_warning(), Field::set_datetime_warning() now use current_thd to get thd if table isn't set.
sql/item_cmpfunc.cc:
  Fixed bug#16377: result of DATE/TIME functions were compared as strings which
  can lead to a wrong result.
  The agg_cmp_type() function now accepts THD as one of parameters. 
  In addition, it now checks if a date/time field/function is present in the
  list. If so, it tries to coerce all constants to INT to make date/time
  comparison return correct result. The field for the constant coercion is
  taken from the Item_field or constructed from the Item_func. In latter case
  the constructed field will be freed after conversion of all constant items.
  Otherwise the result is same as before - aggregated with help of the
  item_cmp_type() function.
sql/item.h:
  The new function result_as_longlong() is added to the Item class. 
  It indicates that the item is a date/time item and result of it can be
  compared as int. Such items are date/time fields/functions.
mysql-test/t/func_time.test:
  Added test case fot bug#16377: result of DATE/TIME functions were compared as strings which
  can lead to a wrong result.
mysql-test/r/func_time.result:
  Added test case fot bug#16377: result of DATE/TIME functions were compared as strings which
  can lead to a wrong result.

1 files changed, 60 insertions, 0 deletions

diff --git a/sql/item_timefunc.cc b/sql/item_timefunc.cc
index 5fdbd968df1..f7b4c9dd630 100644
--- a/sql/item_timefunc.cc
+++ b/sql/item_timefunc.cc
@@ -2306,6 +2306,20 @@ String *Item_datetime_typecast::val_str(String *str)
 }
 
 
+longlong Item_datetime_typecast::val_int()
+{
+  DBUG_ASSERT(fixed == 1);
+  TIME ltime;
+  if (get_arg0_date(&ltime,1))
+  {
+    null_value= 1;
+    return 0;
+  }
+
+  return TIME_to_ulonglong_datetime(&ltime);
+}
+
+
 bool Item_time_typecast::get_time(TIME *ltime)
 {
   bool res= get_arg0_time(ltime);
@@ -2320,6 +2334,17 @@ bool Item_time_typecast::get_time(TIME *ltime)
 }
 
 
+longlong Item_time_typecast::val_int()
+{
+  TIME ltime;
+  if (get_time(&ltime))
+  {
+    null_value= 1;
+    return 0;
+  }
+  return ltime.hour * 10000L + ltime.minute * 100 + ltime.second;
+}
+
 String *Item_time_typecast::val_str(String *str)
 {
   DBUG_ASSERT(fixed == 1);
@@ -2359,6 +2384,14 @@ String *Item_date_typecast::val_str(String *str)
   return 0;
 }
 
+longlong Item_date_typecast::val_int()
+{
+  DBUG_ASSERT(fixed == 1);
+  TIME ltime;
+  if (args[0]->get_date(&ltime, TIME_FUZZY_DATE))
+    return 0;
+  return (longlong) (ltime.year * 10000L + ltime.month * 100 + ltime.day);
+}
 
 /*
   MAKEDATE(a,b) is a date function that creates a date value 
@@ -2395,6 +2428,33 @@ err:
 }
 
 
+longlong Item_func_makedate::val_int()
+{
+  DBUG_ASSERT(fixed == 1);
+  TIME l_time;
+  long daynr=  (long) args[1]->val_int();
+  long yearnr= (long) args[0]->val_int();
+  long days;
+
+  if (args[0]->null_value || args[1]->null_value ||
+      yearnr < 0 || daynr <= 0)
+    goto err;
+
+  days= calc_daynr(yearnr,1,1) + daynr - 1;
+  /* Day number from year 0 to 9999-12-31 */
+  if (days >= 0 && days < MAX_DAY_NUMBER)
+  {
+    null_value=0;
+    get_date_from_daynr(days,&l_time.year,&l_time.month,&l_time.day);
+    return (longlong) (l_time.year * 10000L + l_time.month * 100 + l_time.day);
+  }
+
+err:
+  null_value= 1;
+  return 0;
+}
+
+
 void Item_func_add_time::fix_length_and_dec()
 {
   enum_field_types arg0_field_type;