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

@@ -192,7 +192,7 @@ cast("2001-1-1" as datetime) = "2001-01-01 00:00:00"
 1
 select cast("1:2:3" as TIME) = "1:02:03";
 cast("1:2:3" as TIME) = "1:02:03"
-0
+1
 select cast(NULL as DATE);
 cast(NULL as DATE)
 NULL

mysql-test/r/func_time.result

@@ -630,3 +630,44 @@ select monthname(str_to_date(null, '%m')), monthname(str_to_date(null, '%m')),
 monthname(str_to_date(1, '%m')), monthname(str_to_date(0, '%m'));
 monthname(str_to_date(null, '%m'))	monthname(str_to_date(null, '%m'))	monthname(str_to_date(1, '%m'))	monthname(str_to_date(0, '%m'))
 NULL	NULL	January	NULL
+create table t1(f1 date, f2 time, f3 datetime);
+insert into t1 values ("2006-01-01", "12:01:01", "2006-01-01 12:01:01");
+insert into t1 values ("2006-01-02", "12:01:02", "2006-01-02 12:01:02");
+select f1 from t1 where f1 between "2006-1-1" and 20060101;
+f1
+2006-01-01
+select f1 from t1 where f1 between "2006-1-1" and "2006.1.1";
+f1
+2006-01-01
+select f1 from t1 where date(f1) between "2006-1-1" and "2006.1.1";
+f1
+2006-01-01
+select f2 from t1 where f2 between "12:1:2" and "12:2:2";
+f2
+12:01:02
+select f2 from t1 where time(f2) between "12:1:2" and "12:2:2";
+f2
+12:01:02
+select f3 from t1 where f3 between "2006-1-1 12:1:1" and "2006-1-1 12:1:2";
+f3
+2006-01-01 12:01:01
+select f3 from t1 where timestamp(f3) between "2006-1-1 12:1:1" and "2006-1-1 12:1:2";
+f3
+2006-01-01 12:01:01
+select f1 from t1 where "2006-1-1" between f1 and f3;
+f1
+2006-01-01
+select f1 from t1 where "2006-1-1" between date(f1) and date(f3);
+f1
+2006-01-01
+select f1 from t1 where "2006-1-1" between f1 and 'zzz';
+f1
+Warnings:
+Warning	1292	Truncated incorrect date value: 'zzz'
+select f1 from t1 where makedate(2006,1) between date(f1) and date(f3);
+f1
+2006-01-01
+select f1 from t1 where makedate(2006,2) between date(f1) and date(f3);
+f1
+2006-01-02
+drop table t1;

mysql-test/t/func_time.test

@@ -322,4 +322,24 @@ select last_day('2005-01-00');
 select monthname(str_to_date(null, '%m')), monthname(str_to_date(null, '%m')),
        monthname(str_to_date(1, '%m')), monthname(str_to_date(0, '%m'));
 
+#
+# Bug#16377 result of DATE/TIME functions were compared as strings which
+#           can lead to a wrong result.
+#
+create table t1(f1 date, f2 time, f3 datetime);
+insert into t1 values ("2006-01-01", "12:01:01", "2006-01-01 12:01:01");
+insert into t1 values ("2006-01-02", "12:01:02", "2006-01-02 12:01:02");
+select f1 from t1 where f1 between "2006-1-1" and 20060101;
+select f1 from t1 where f1 between "2006-1-1" and "2006.1.1";
+select f1 from t1 where date(f1) between "2006-1-1" and "2006.1.1";
+select f2 from t1 where f2 between "12:1:2" and "12:2:2";
+select f2 from t1 where time(f2) between "12:1:2" and "12:2:2";
+select f3 from t1 where f3 between "2006-1-1 12:1:1" and "2006-1-1 12:1:2";
+select f3 from t1 where timestamp(f3) between "2006-1-1 12:1:1" and "2006-1-1 12:1:2";
+select f1 from t1 where "2006-1-1" between f1 and f3;
+select f1 from t1 where "2006-1-1" between date(f1) and date(f3);
+select f1 from t1 where "2006-1-1" between f1 and 'zzz';
+select f1 from t1 where makedate(2006,1) between date(f1) and date(f3);
+select f1 from t1 where makedate(2006,2) between date(f1) and date(f3);
+drop table t1;
 # End of 4.1 tests

sql/field.cc

@@ -6841,7 +6841,11 @@ create_field::create_field(Field *old_field,Field *orig_field)
 bool 
 Field::set_warning(const uint level, const uint code, int cuted_increment)
 {
-  THD *thd= table->in_use;
+  /*
+    If this field was created only for type conversion purposes it
+    will have table == NULL.
+  */
+  THD *thd= table ? table->in_use : current_thd;
   if (thd->count_cuted_fields)
   {
     thd->cuted_fields+= cuted_increment;
@@ -6876,7 +6880,8 @@ Field::set_datetime_warning(const uint level, const uint code,
                             timestamp_type ts_type, int cuted_increment)
 {
   if (set_warning(level, code, cuted_increment))
-    make_truncated_value_warning(table->in_use, str, str_length, ts_type);
+    make_truncated_value_warning(table ? table->in_use : current_thd,
+                                 str, str_length, ts_type);
 }
 
 
@@ -6905,8 +6910,8 @@ Field::set_datetime_warning(const uint level, const uint code,
   {
     char str_nr[22];
     char *str_end= longlong10_to_str(nr, str_nr, -10);
-    make_truncated_value_warning(table->in_use, str_nr, str_end - str_nr, 
-                                 ts_type);
+    make_truncated_value_warning(table ? table->in_use : current_thd,
+                                 str_nr, str_end - str_nr, ts_type);
   }
 }
 
@@ -6935,7 +6940,8 @@ Field::set_datetime_warning(const uint level, const uint code,
     /* DBL_DIG is enough to print '-[digits].E+###' */
     char str_nr[DBL_DIG + 8];
     uint str_len= my_sprintf(str_nr, (str_nr, "%g", nr));
-    make_truncated_value_warning(table->in_use, str_nr, str_len, ts_type);
+    make_truncated_value_warning(table ? table->in_use : current_thd,
+                                 str_nr, str_len, ts_type);
   }
 }
 

sql/item.h

@@ -327,6 +327,14 @@ public:
     cleanup();
     delete this;
   }
+  /*
+    result_as_longlong() must return TRUE for Items representing DATE/TIME
+    functions and DATE/TIME table fields.
+    Those Items have result_type()==STRING_RESULT (and not INT_RESULT), but
+    their values should be compared as integers (because the integer
+    representation is more precise than the string one).
+  */
+  virtual bool result_as_longlong() { return FALSE; }
 };
 
 
@@ -450,6 +458,10 @@ public:
   Item *get_tmp_table_item(THD *thd);
   void cleanup();
   inline uint32 max_disp_length() { return field->max_length(); }
+  bool result_as_longlong()
+  {
+    return field->can_be_compared_as_longlong();
+  }
   friend class Item_default_value;
   friend class Item_insert_value;
   friend class st_select_lex_unit;
@@ -973,6 +985,10 @@ public:
   }
   Item *real_item() { return *ref; }
   void print(String *str);
+  bool result_as_longlong()
+  {
+    return (*ref)->result_as_longlong();
+  }
 };
 
 

sql/item_cmpfunc.cc

@@ -25,6 +25,8 @@
 #include <m_ctype.h>
 #include "sql_select.h"
 
+static bool convert_constant_item(THD *thd, Field *field, Item **item);
+
 static Item_result item_store_type(Item_result a,Item_result b)
 {
   if (a == STRING_RESULT || b == STRING_RESULT)
@@ -64,6 +66,7 @@ static void agg_result_type(Item_result *type, Item **items, uint nitems)
 
   SYNOPSIS:
     agg_cmp_type()
+    thd          thread handle
     type   [out] the aggregated type
     items        array of items to aggregate the type from
     nitems       number of items in the array
@@ -78,24 +81,133 @@ static void agg_result_type(Item_result *type, Item **items, uint nitems)
     If all items are constants the type will be aggregated from all items.
     If there are some non-constant items then only types of non-constant
     items will be used for aggregation.
+    If there are DATE/TIME fields/functions in the list and no string
+    fields/functions in the list then:
+      The INT_RESULT type will be used for aggregation instead of orginal
+      result type of any DATE/TIME field/function in the list
+      All constant items in the list will be converted to a DATE/TIME using
+      found field or result field of found function.
+
+    Implementation notes:
+      The code is equvalent to:
+      1. Check the list for presense of a STRING field/function.
+         Collect the is_const flag.
+      2. Get a Field* object to use for type coercion
+      3. Perform type conversion.
+      1 and 2 are implemented in 2 loops. The first searches for a DATE/TIME
+      field/function and checks presense of a STRING field/function.
+      The second loop works only if a DATE/TIME field/function is found.
+      It checks presense of a STRING field/function in the rest of the list.
+
+  TODO
+    1) The current implementation can produce false comparison results for
+    expressions like:
+      date_time_field BETWEEN string_field_with_dates AND string_constant
+    if the string_constant will omit some of leading zeroes.
+    In order to fully implement correct comparison of DATE/TIME the new
+    DATETIME_RESULT result type should be introduced and agg_cmp_type()
+    should return the DATE/TIME field used for the conversion. Later
+    this field can be used by comparison functions like Item_func_between to
+    convert string values to ints on the fly and thus return correct results.
+    This modification will affect functions BETWEEN, IN and CASE.
+
+    2) If in the list a DATE field/function and a DATETIME field/function
+    are present in the list then the first found field/function will be
+    used for conversion. This may lead to wrong results and probably should
+    be fixed.
 */
-static void agg_cmp_type(Item_result *type, Item **items, uint nitems)
+
+static void agg_cmp_type(THD *thd, Item_result *type, Item **items, uint nitems)
 {
   uint i;
-  type[0]= items[0]->result_type();
+  Item::Type res;
+  char *buff= NULL;
+  uchar null_byte;
+  Field *field= NULL;
+
+  /* Search for date/time fields/functions */
+  for (i= 0; i < nitems; i++)
+  {
+    if (!items[i]->result_as_longlong())
+    {
+      /* Do not convert anything if a string field/function is present */
+      if (!items[i]->const_item() && items[i]->result_type() == STRING_RESULT)
+      {
+        i= nitems;
+        break;
+      }
+      continue;
+    }
+    if ((res= items[i]->real_item()->type()) == Item::FIELD_ITEM)
+    {
+      field= ((Item_field *)items[i]->real_item())->field;
+      break;
+    }
+    else if (res == Item::FUNC_ITEM)
+    {
+      field= items[i]->tmp_table_field_from_field_type(0);
+      if (field)
+        buff= alloc_root(thd->mem_root, field->max_length());
+      if (!buff || !field)
+      {
+        if (field)
+          delete field;
+        if (buff)
+          my_free(buff, MYF(MY_WME));
+        field= 0;
+      }
+      else
+        field->move_field(buff, &null_byte, 0);
+      break;
+    }
+  }
+  if (field)
+  {
+    /* Check the rest of the list for presense of a string field/function. */
+    for (i++ ; i < nitems; i++)
+    {
+      if (!items[i]->const_item() && items[i]->result_type() == STRING_RESULT &&
+          !items[i]->result_as_longlong())
+      {
+        field= 0;
+        break;
+      }
+    }
+  }
   /* Reset to 0 on first occurence of non-const item. 1 otherwise */
   bool is_const= items[0]->const_item();
+  /*
+    If the first item is a date/time function then its result should be
+    compared as int
+  */
+  if (field)
+  {
+    /* Suppose we are comparing dates and some non-constant items are present. */
+    type[0]= INT_RESULT;
+    is_const= 0;
+  }
+  else
+    type[0]= items[0]->result_type();
 
-  for (i= 1 ; i < nitems ; i++)
+  for (i= 0; i < nitems ; i++)
   {
     if (!items[i]->const_item())
     {
-      type[0]= is_const ? items[i]->result_type() :
-                 item_cmp_type(type[0], items[i]->result_type());
+      Item_result result= field && items[i]->result_as_longlong() ?
+                            INT_RESULT : items[i]->result_type();
+      type[0]= is_const ? result : item_cmp_type(type[0], result);
       is_const= 0;
     }
     else if (is_const)
       type[0]= item_cmp_type(type[0], items[i]->result_type());
+    else if (field)
+      convert_constant_item(thd, field, &items[i]);
+  }
+
+  if (res == Item::FUNC_ITEM && field)
+  {
+    delete field;
+    my_free(buff, MYF(MY_WME));
   }
 }
 
@@ -929,31 +1041,9 @@ void Item_func_between::fix_length_and_dec()
   */
   if (!args[0] || !args[1] || !args[2])
     return;
-  agg_cmp_type(&cmp_type, args, 3);
-  if (cmp_type == STRING_RESULT &&
-      agg_arg_charsets(cmp_collation, args, 3, MY_COLL_CMP_CONV))
-    return;
-
-  /*
-    Make a special case of compare with date/time and longlong fields.
-    They are compared as integers, so for const item this time-consuming
-    conversion can be done only once, not for every single comparison
-  */
-  if (args[0]->type() == FIELD_ITEM)
-  {
-    Field *field=((Item_field*) args[0])->field;
-    if (field->can_be_compared_as_longlong())
-    {
-      /*
-        The following can't be recoded with || as convert_constant_item
-        changes the argument
-      */
-      if (convert_constant_item(thd, field,&args[1]))
-	cmp_type=INT_RESULT;			// Works for all types.
-      if (convert_constant_item(thd, field,&args[2]))
-	cmp_type=INT_RESULT;			// Works for all types.
-    }
-  }
+  agg_cmp_type(thd, &cmp_type, args, 3);
+  if (cmp_type == STRING_RESULT)
+      agg_arg_charsets(cmp_collation, args, 3, MY_COLL_CMP_CONV);
 }
 
 
@@ -1477,7 +1567,7 @@ void Item_func_case::fix_length_and_dec()
     for (nagg= 0; nagg < ncases/2 ; nagg++)
       agg[nagg+1]= args[nagg*2];
     nagg++;
-    agg_cmp_type(&cmp_type, agg, nagg);
+    agg_cmp_type(current_thd, &cmp_type, agg, nagg);
     if ((cmp_type == STRING_RESULT) &&
         agg_arg_charsets(cmp_collation, agg, nagg, MY_COLL_CMP_CONV))
     return;
@@ -1958,7 +2048,7 @@ void Item_func_in::fix_length_and_dec()
   uint const_itm= 1;
   THD *thd= current_thd;
   
-  agg_cmp_type(&cmp_type, args, arg_count);
+  agg_cmp_type(thd, &cmp_type, args, arg_count);
 
   if (cmp_type == STRING_RESULT &&
       agg_arg_charsets(cmp_collation, args, arg_count, MY_COLL_CMP_CONV))

sql/item_cmpfunc.h

@@ -43,8 +43,11 @@ public:
   int set_compare_func(Item_bool_func2 *owner, Item_result type);
   inline int set_compare_func(Item_bool_func2 *owner_arg)
   {
-    return set_compare_func(owner_arg, item_cmp_type((*a)->result_type(),
-						     (*b)->result_type()));
+    Item_result ar= (*a)->result_as_longlong() && (*b)->const_item() ?
+                      INT_RESULT : (*a)->result_type();
+    Item_result br= (*b)->result_as_longlong() && (*a)->const_item() ?
+                      INT_RESULT : (*b)->result_type();
+    return set_compare_func(owner_arg, item_cmp_type(ar, br));
   }
   inline int set_cmp_func(Item_bool_func2 *owner_arg,
 			  Item **a1, Item **a2,
@@ -57,8 +60,11 @@ public:
   inline int set_cmp_func(Item_bool_func2 *owner_arg,
 			  Item **a1, Item **a2)
   {
-    return set_cmp_func(owner_arg, a1, a2, item_cmp_type((*a1)->result_type(),
-							 (*a2)->result_type()));
+    Item_result ar= (*a1)->result_as_longlong() && (*a2)->const_item() ?
+                      INT_RESULT : (*a1)->result_type();
+    Item_result br= (*a2)->result_as_longlong() && (*a1)->const_item() ?
+                      INT_RESULT : (*a2)->result_type();
+    return set_cmp_func(owner_arg, a1, a2, item_cmp_type(ar, br));
   }
   inline int compare() { return (this->*func)(); }
 

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;

sql/item_timefunc.h

@@ -339,6 +339,7 @@ public:
   {
     return (new Field_date(maybe_null, name, t_arg, &my_charset_bin));
   }  
+  bool result_as_longlong() { return TRUE; }
 };
 
 
@@ -354,6 +355,7 @@ public:
   {
     return (new Field_datetime(maybe_null, name, t_arg, &my_charset_bin));
   }
+  bool result_as_longlong() { return TRUE; }
 };
 
 
@@ -383,6 +385,7 @@ public:
     TIME representation using UTC-SYSTEM or per-thread time zone.
   */
   virtual void store_now_in_TIME(TIME *now_time)=0;
+  bool result_as_longlong() { return TRUE; }
 };
 
 
@@ -588,6 +591,7 @@ public:
   {
     return (new Field_time(maybe_null, name, t_arg, &my_charset_bin));
   }
+  bool result_as_longlong() { return TRUE; }
 };
 
 /*
@@ -715,6 +719,8 @@ public:
     max_length= 10;
     maybe_null= 1;
   }
+  bool result_as_longlong() { return TRUE; }
+  longlong val_int();
 };
 
 
@@ -731,6 +737,8 @@ public:
   {
     return (new Field_time(maybe_null, name, t_arg, &my_charset_bin));
   }
+  bool result_as_longlong() { return TRUE; }
+  longlong val_int();
 };
 
 
@@ -746,6 +754,8 @@ public:
   {
     return (new Field_datetime(maybe_null, name, t_arg, &my_charset_bin));
   }
+  bool result_as_longlong() { return TRUE; }
+  longlong val_int();
 };
 
 class Item_func_makedate :public Item_str_func
@@ -764,6 +774,8 @@ public:
   {
     return (new Field_date(maybe_null, name, t_arg, &my_charset_bin));
   }
+  bool result_as_longlong() { return TRUE; }
+  longlong val_int();
 };