Backport into build-200911241145-5.1.40sp1

> ------------------------------------------------------------
> revno: 3148.9.6
> revision-id: martin.hansson@sun.com-20091102122407-krzh4h0i052lbwr5
> parent: davi.arnaut@sun.com-20091102112236-k3myix2xy8miyv4s
> committer: Martin Hansson <martin.hansson@sun.com>
> branch nick: 5.1bt
> timestamp: Mon 2009-11-02 13:24:07 +0100
> message:
>   Bug#47925: regression of range optimizer and date comparison in 5.1.39!
>   
>   When a query was using a DATE or DATETIME value formatted
>   using any other separator characters beside hyphen '-', a
>   query with a greater-or-equal '>=' condition matching only
>   the greatest value in an indexed column, the result was
>   empty if index range scan was employed.
>   
>   The range optimizer got a new feature between 5.1.38 and
>   5.1.39 that changes a greater-or-equal condition to a
>   greater-than if the value matching that in the query was not
>   present in the table. But the value comparison function
>   compared the dates as strings instead of dates.
>   
>   The bug was fixed by splitting the function
>   get_date_from_str in two: One part that parses and does
>   error checking. This function is now visible outside the
>   module. The old get_date_from_str now calls the new
>   function.

mysql-test/r/range.result

@@ -1219,3 +1219,201 @@ explain select * from t2 where a=1000 and b<11;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t2	ref	a	a	5	const	502	Using where
 drop table t1, t2;
+#
+# Bug#47925: regression of range optimizer and date comparison in 5.1.39!
+#
+CREATE TABLE t1 ( a DATE,     KEY ( a ) );
+CREATE TABLE t2 ( a DATETIME, KEY ( a ) );
+# Make optimizer choose range scan
+INSERT INTO t1 VALUES ('2009-09-22'), ('2009-09-22'), ('2009-09-22');
+INSERT INTO t1 VALUES ('2009-09-23'), ('2009-09-23'), ('2009-09-23');
+INSERT INTO t2 VALUES ('2009-09-22 12:00:00'), ('2009-09-22 12:00:00'),
+('2009-09-22 12:00:00');
+INSERT INTO t2 VALUES ('2009-09-23 12:00:00'), ('2009-09-23 12:00:00'),
+('2009-09-23 12:00:00');
+# DATE vs DATE
+EXPLAIN
+SELECT * FROM t1 WHERE a >= '2009/09/23';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+X	X	X	range	a	a	X	X	X	X
+SELECT * FROM t1 WHERE a >= '2009/09/23';
+a
+2009-09-23
+2009-09-23
+2009-09-23
+SELECT * FROM t1 WHERE a >= '20090923';
+a
+2009-09-23
+2009-09-23
+2009-09-23
+SELECT * FROM t1 WHERE a >=  20090923;
+a
+2009-09-23
+2009-09-23
+2009-09-23
+SELECT * FROM t1 WHERE a >= '2009-9-23';
+a
+2009-09-23
+2009-09-23
+2009-09-23
+SELECT * FROM t1 WHERE a >= '2009.09.23';
+a
+2009-09-23
+2009-09-23
+2009-09-23
+SELECT * FROM t1 WHERE a >= '2009:09:23';
+a
+2009-09-23
+2009-09-23
+2009-09-23
+# DATE vs DATETIME
+EXPLAIN
+SELECT * FROM t2 WHERE a >= '2009/09/23';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+X	X	X	range	a	a	X	X	X	X
+SELECT * FROM t2 WHERE a >= '2009/09/23';
+a
+2009-09-23 12:00:00
+2009-09-23 12:00:00
+2009-09-23 12:00:00
+SELECT * FROM t2 WHERE a >= '2009/09/23';
+a
+2009-09-23 12:00:00
+2009-09-23 12:00:00
+2009-09-23 12:00:00
+SELECT * FROM t2 WHERE a >= '20090923';
+a
+2009-09-23 12:00:00
+2009-09-23 12:00:00
+2009-09-23 12:00:00
+SELECT * FROM t2 WHERE a >=  20090923;
+a
+2009-09-23 12:00:00
+2009-09-23 12:00:00
+2009-09-23 12:00:00
+SELECT * FROM t2 WHERE a >= '2009-9-23';
+a
+2009-09-23 12:00:00
+2009-09-23 12:00:00
+2009-09-23 12:00:00
+SELECT * FROM t2 WHERE a >= '2009.09.23';
+a
+2009-09-23 12:00:00
+2009-09-23 12:00:00
+2009-09-23 12:00:00
+SELECT * FROM t2 WHERE a >= '2009:09:23';
+a
+2009-09-23 12:00:00
+2009-09-23 12:00:00
+2009-09-23 12:00:00
+# DATETIME vs DATETIME
+EXPLAIN
+SELECT * FROM t2 WHERE a >= '2009/09/23 12:00:00';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+X	X	X	range	a	a	X	X	X	X
+SELECT * FROM t2 WHERE a >= '2009/09/23 12:00:00';
+a
+2009-09-23 12:00:00
+2009-09-23 12:00:00
+2009-09-23 12:00:00
+SELECT * FROM t2 WHERE a >= '20090923120000';
+a
+2009-09-23 12:00:00
+2009-09-23 12:00:00
+2009-09-23 12:00:00
+SELECT * FROM t2 WHERE a >=  20090923120000;
+a
+2009-09-23 12:00:00
+2009-09-23 12:00:00
+2009-09-23 12:00:00
+SELECT * FROM t2 WHERE a >= '2009-9-23 12:00:00';
+a
+2009-09-23 12:00:00
+2009-09-23 12:00:00
+2009-09-23 12:00:00
+SELECT * FROM t2 WHERE a >= '2009.09.23 12:00:00';
+a
+2009-09-23 12:00:00
+2009-09-23 12:00:00
+2009-09-23 12:00:00
+SELECT * FROM t2 WHERE a >= '2009:09:23 12:00:00';
+a
+2009-09-23 12:00:00
+2009-09-23 12:00:00
+2009-09-23 12:00:00
+# DATETIME vs DATE
+EXPLAIN
+SELECT * FROM t1 WHERE a >= '2009/09/23 00:00:00';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+X	X	X	range	a	a	X	X	X	X
+SELECT * FROM t1 WHERE a >= '2009/09/23 00:00:00';
+a
+2009-09-23
+2009-09-23
+2009-09-23
+SELECT * FROM t1 WHERE a >= '2009/09/23 00:00:00';
+a
+2009-09-23
+2009-09-23
+2009-09-23
+SELECT * FROM t1 WHERE a >= '20090923000000';
+a
+2009-09-23
+2009-09-23
+2009-09-23
+SELECT * FROM t1 WHERE a >=  20090923000000;
+a
+2009-09-23
+2009-09-23
+2009-09-23
+SELECT * FROM t1 WHERE a >= '2009-9-23 00:00:00';
+a
+2009-09-23
+2009-09-23
+2009-09-23
+SELECT * FROM t1 WHERE a >= '2009.09.23 00:00:00';
+a
+2009-09-23
+2009-09-23
+2009-09-23
+SELECT * FROM t1 WHERE a >= '2009:09:23 00:00:00';
+a
+2009-09-23
+2009-09-23
+2009-09-23
+# Test of the new get_date_from_str implementation
+# Behavior differs slightly between the trunk and mysql-pe.
+# The former may give errors for the truncated values, while the latter
+# gives warnings. The purpose of this test is not to interfere, and only
+# preserve existing behavior.
+SELECT str_to_date('2007-10-00', '%Y-%m-%d') >= '' AND 
+str_to_date('2007-10-00', '%Y-%m-%d') <= '2007/10/20';
+str_to_date('2007-10-00', '%Y-%m-%d') >= '' AND 
+str_to_date('2007-10-00', '%Y-%m-%d') <= '2007/10/20'
+1
+Warnings:
+Warning	1292	Truncated incorrect date value: ''
+SELECT str_to_date('2007-20-00', '%Y-%m-%d') >= '2007/10/20' AND 
+str_to_date('2007-20-00', '%Y-%m-%d') <= '';
+str_to_date('2007-20-00', '%Y-%m-%d') >= '2007/10/20' AND 
+str_to_date('2007-20-00', '%Y-%m-%d') <= ''
+NULL
+Warnings:
+Warning	1292	Truncated incorrect date value: ''
+Error	1411	Incorrect datetime value: '2007-20-00' for function str_to_date
+Error	1411	Incorrect datetime value: '2007-20-00' for function str_to_date
+SELECT str_to_date('2007-10-00', '%Y-%m-%d') BETWEEN '' AND '2007/10/20';
+str_to_date('2007-10-00', '%Y-%m-%d') BETWEEN '' AND '2007/10/20'
+1
+Warnings:
+Warning	1292	Truncated incorrect datetime value: ''
+SELECT str_to_date('2007-20-00', '%Y-%m-%d') BETWEEN '2007/10/20' AND '';
+str_to_date('2007-20-00', '%Y-%m-%d') BETWEEN '2007/10/20' AND ''
+NULL
+Warnings:
+Error	1411	Incorrect datetime value: '2007-20-00' for function str_to_date
+SELECT str_to_date('', '%Y-%m-%d');
+str_to_date('', '%Y-%m-%d')
+0000-00-00
+DROP TABLE t1, t2;
+End of 5.1 tests

mysql-test/t/range.test

@@ -1046,3 +1046,83 @@ explain select * from t2 where a=1000 and b<11;
 
 drop table t1, t2;
 
+--echo #
+--echo # Bug#47925: regression of range optimizer and date comparison in 5.1.39!
+--echo #
+CREATE TABLE t1 ( a DATE,     KEY ( a ) );
+CREATE TABLE t2 ( a DATETIME, KEY ( a ) );
+
+--echo # Make optimizer choose range scan
+INSERT INTO t1 VALUES ('2009-09-22'), ('2009-09-22'), ('2009-09-22');
+INSERT INTO t1 VALUES ('2009-09-23'), ('2009-09-23'), ('2009-09-23');
+
+INSERT INTO t2 VALUES ('2009-09-22 12:00:00'), ('2009-09-22 12:00:00'),
+                      ('2009-09-22 12:00:00');
+INSERT INTO t2 VALUES ('2009-09-23 12:00:00'), ('2009-09-23 12:00:00'),
+                      ('2009-09-23 12:00:00');
+
+--echo # DATE vs DATE
+--replace_column 1 X 2 X 3 X 7 X 8 X 9 X 10 X
+EXPLAIN
+SELECT * FROM t1 WHERE a >= '2009/09/23';
+SELECT * FROM t1 WHERE a >= '2009/09/23';
+SELECT * FROM t1 WHERE a >= '20090923';
+SELECT * FROM t1 WHERE a >=  20090923;
+SELECT * FROM t1 WHERE a >= '2009-9-23';
+SELECT * FROM t1 WHERE a >= '2009.09.23';
+SELECT * FROM t1 WHERE a >= '2009:09:23';
+
+--echo # DATE vs DATETIME
+--replace_column 1 X 2 X 3 X 7 X 8 X 9 X 10 X
+EXPLAIN
+SELECT * FROM t2 WHERE a >= '2009/09/23';
+SELECT * FROM t2 WHERE a >= '2009/09/23';
+SELECT * FROM t2 WHERE a >= '2009/09/23';
+SELECT * FROM t2 WHERE a >= '20090923';
+SELECT * FROM t2 WHERE a >=  20090923;
+SELECT * FROM t2 WHERE a >= '2009-9-23';
+SELECT * FROM t2 WHERE a >= '2009.09.23';
+SELECT * FROM t2 WHERE a >= '2009:09:23';
+
+--echo # DATETIME vs DATETIME
+--replace_column 1 X 2 X 3 X 7 X 8 X 9 X 10 X
+EXPLAIN
+SELECT * FROM t2 WHERE a >= '2009/09/23 12:00:00';
+SELECT * FROM t2 WHERE a >= '2009/09/23 12:00:00';
+SELECT * FROM t2 WHERE a >= '20090923120000';
+SELECT * FROM t2 WHERE a >=  20090923120000;
+SELECT * FROM t2 WHERE a >= '2009-9-23 12:00:00';
+SELECT * FROM t2 WHERE a >= '2009.09.23 12:00:00';
+SELECT * FROM t2 WHERE a >= '2009:09:23 12:00:00';
+
+--echo # DATETIME vs DATE
+--replace_column 1 X 2 X 3 X 7 X 8 X 9 X 10 X
+EXPLAIN
+SELECT * FROM t1 WHERE a >= '2009/09/23 00:00:00';
+SELECT * FROM t1 WHERE a >= '2009/09/23 00:00:00';
+SELECT * FROM t1 WHERE a >= '2009/09/23 00:00:00';
+SELECT * FROM t1 WHERE a >= '20090923000000';
+SELECT * FROM t1 WHERE a >=  20090923000000;
+SELECT * FROM t1 WHERE a >= '2009-9-23 00:00:00';
+SELECT * FROM t1 WHERE a >= '2009.09.23 00:00:00';
+SELECT * FROM t1 WHERE a >= '2009:09:23 00:00:00';
+
+--echo # Test of the new get_date_from_str implementation
+--echo # Behavior differs slightly between the trunk and mysql-pe.
+--echo # The former may give errors for the truncated values, while the latter
+--echo # gives warnings. The purpose of this test is not to interfere, and only
+--echo # preserve existing behavior.
+SELECT str_to_date('2007-10-00', '%Y-%m-%d') >= '' AND 
+       str_to_date('2007-10-00', '%Y-%m-%d') <= '2007/10/20';
+
+SELECT str_to_date('2007-20-00', '%Y-%m-%d') >= '2007/10/20' AND 
+       str_to_date('2007-20-00', '%Y-%m-%d') <= '';
+
+SELECT str_to_date('2007-10-00', '%Y-%m-%d') BETWEEN '' AND '2007/10/20';
+SELECT str_to_date('2007-20-00', '%Y-%m-%d') BETWEEN '2007/10/20' AND '';
+
+SELECT str_to_date('', '%Y-%m-%d');
+
+DROP TABLE t1, t2;
+
+--echo End of 5.1 tests

sql/item.cc

@@ -6859,52 +6859,61 @@ void resolve_const_item(THD *thd, Item **ref, Item *comp_item)
 }
 
 /**
-  Compare the value stored in field, with the original item.
+  Compare the value stored in field with the expression from the query.
 
-  @param field   field which the item is converted and stored in
-  @param item    original item
+  @param field   Field which the Item is stored in after conversion
+  @param item    Original expression from query
 
-  @return Return an integer greater than, equal to, or less than 0 if
+  @return Returns an integer greater than, equal to, or less than 0 if
           the value stored in the field is greater than, equal to,
-          or less than the original item
+          or less than the original Item. A 0 may also be returned if 
+          out of memory.          
 
   @note We only use this on the range optimizer/partition pruning,
         because in some cases we can't store the value in the field
         without some precision/character loss.
 */
 
-int stored_field_cmp_to_item(Field *field, Item *item)
+int stored_field_cmp_to_item(THD *thd, Field *field, Item *item)
 {
-
   Item_result res_type=item_cmp_type(field->result_type(),
 				     item->result_type());
   if (res_type == STRING_RESULT)
   {
     char item_buff[MAX_FIELD_WIDTH];
     char field_buff[MAX_FIELD_WIDTH];
-    String item_tmp(item_buff,sizeof(item_buff),&my_charset_bin),*item_result;
+    
+    String item_tmp(item_buff,sizeof(item_buff),&my_charset_bin);
     String field_tmp(field_buff,sizeof(field_buff),&my_charset_bin);
-    enum_field_types field_type;
-    item_result=item->val_str(&item_tmp);
+    String *item_result= item->val_str(&item_tmp);
+    /*
+      Some implementations of Item::val_str(String*) actually modify
+      the field Item::null_value, hence we can't check it earlier.
+    */
     if (item->null_value)
       return 0;
-    field->val_str(&field_tmp);
+    String *field_result= field->val_str(&field_tmp);
 
-    /*
-      If comparing DATE with DATETIME, append the time-part to the DATE.
-      So that the strings are equally formatted.
-      A DATE converted to string is 10 characters, and a DATETIME converted
-      to string is 19 characters.
-    */
-    field_type= field->type();
-    if (field_type == MYSQL_TYPE_DATE &&
-        item_result->length() == 19)
-      field_tmp.append(" 00:00:00");
-    else if (field_type == MYSQL_TYPE_DATETIME &&
-             item_result->length() == 10)
-      item_result->append(" 00:00:00");
-
-    return stringcmp(&field_tmp,item_result);
+    enum_field_types field_type= field->type();
+
+    if (field_type == MYSQL_TYPE_DATE || field_type == MYSQL_TYPE_DATETIME)
+    {
+      enum_mysql_timestamp_type type= MYSQL_TIMESTAMP_ERROR;
+
+      if (field_type == MYSQL_TYPE_DATE)
+        type= MYSQL_TIMESTAMP_DATE;
+
+      if (field_type == MYSQL_TYPE_DATETIME)
+        type= MYSQL_TIMESTAMP_DATETIME;
+        
+      const char *field_name= field->field_name;
+      MYSQL_TIME field_time, item_time;
+      get_mysql_time_from_str(thd, field_result, type, field_name, &field_time);
+      get_mysql_time_from_str(thd, item_result, type, field_name,  &item_time);
+
+      return my_time_compare(&field_time, &item_time);
+    }
+    return stringcmp(field_result, item_result);
   }
   if (res_type == INT_RESULT)
     return 0;					// Both are of type int

sql/item.h

@@ -3124,4 +3124,4 @@ void mark_select_range_as_dependent(THD *thd,
 extern Cached_item *new_Cached_item(THD *thd, Item *item);
 extern Item_result item_cmp_type(Item_result a,Item_result b);
 extern void resolve_const_item(THD *thd, Item **ref, Item *cmp_item);
-extern int stored_field_cmp_to_item(Field *field, Item *item);
+extern int stored_field_cmp_to_item(THD *thd, Field *field, Item *item);

sql/item_cmpfunc.cc

@@ -636,56 +636,51 @@ int Arg_comparator::set_compare_func(Item_bool_func2 *item, Item_result type)
   return 0;
 }
 
-
 /**
-  @brief Convert date provided in a string to the int representation.
-
-  @param[in]   thd        thread handle
-  @param[in]   str        a string to convert
-  @param[in]   warn_type  type of the timestamp for issuing the warning
-  @param[in]   warn_name  field name for issuing the warning
-  @param[out]  error_arg  could not extract a DATE or DATETIME
-
-  @details Convert date provided in the string str to the int
-    representation.  If the string contains wrong date or doesn't
-    contain it at all then a warning is issued.  The warn_type and
-    the warn_name arguments are used as the name and the type of the
-    field when issuing the warning.  If any input was discarded
-    (trailing or non-timestampy characters), was_cut will be non-zero.
-    was_type will return the type str_to_datetime() could correctly
-    extract.
-
-  @return
-    converted value. 0 on error and on zero-dates -- check 'failure'
+  Parse date provided in a string to a MYSQL_TIME.
+
+  @param[in]   thd        Thread handle
+  @param[in]   str        A string to convert
+  @param[in]   warn_type  Type of the timestamp for issuing the warning
+  @param[in]   warn_name  Field name for issuing the warning
+  @param[out]  l_time     The MYSQL_TIME objects is initialized.
+
+  Parses a date provided in the string str into a MYSQL_TIME object. If the
+  string contains an incorrect date or doesn't correspond to a date at all
+  then a warning is issued. The warn_type and the warn_name arguments are used
+  as the name and the type of the field when issuing the warning. If any input
+  was discarded (trailing or non-timestamp-y characters), return value will be
+  TRUE.
+
+  @return Status flag
+  @retval FALSE Success.
+  @retval True Indicates failure.
 */
 
-static ulonglong
-get_date_from_str(THD *thd, String *str, timestamp_type warn_type,
-                  char *warn_name, bool *error_arg)
+bool get_mysql_time_from_str(THD *thd, String *str, timestamp_type warn_type, 
+                             const char *warn_name, MYSQL_TIME *l_time)
 {
-  ulonglong value= 0;
+  bool value;
   int error;
-  MYSQL_TIME l_time;
-  enum_mysql_timestamp_type ret;
+  enum_mysql_timestamp_type timestamp_type;
 
-  ret= str_to_datetime(str->ptr(), str->length(), &l_time,
+  timestamp_type= 
+    str_to_datetime(str->ptr(), str->length(), l_time,
                     (TIME_FUZZY_DATE | MODE_INVALID_DATES |
                      (thd->variables.sql_mode &
                       (MODE_NO_ZERO_IN_DATE | MODE_NO_ZERO_DATE))),
                     &error);
 
-  if (ret == MYSQL_TIMESTAMP_DATETIME || ret == MYSQL_TIMESTAMP_DATE)
-  {
+  if (timestamp_type == MYSQL_TIMESTAMP_DATETIME || 
+      timestamp_type == MYSQL_TIMESTAMP_DATE)
     /*
       Do not return yet, we may still want to throw a "trailing garbage"
       warning.
     */
-    *error_arg= FALSE;
-    value= TIME_to_ulonglong_datetime(&l_time);
-  }
+    value= FALSE;
   else
   {
-    *error_arg= TRUE;
+    value= TRUE;
     error= 1;                                   /* force warning */
   }
 
@@ -698,6 +693,37 @@ get_date_from_str(THD *thd, String *str, timestamp_type warn_type,
 }
 
 
+/**
+  @brief Convert date provided in a string to the int representation.
+
+  @param[in]   thd        thread handle
+  @param[in]   str        a string to convert
+  @param[in]   warn_type  type of the timestamp for issuing the warning
+  @param[in]   warn_name  field name for issuing the warning
+  @param[out]  error_arg  could not extract a DATE or DATETIME
+
+  @details Convert date provided in the string str to the int
+    representation.  If the string contains wrong date or doesn't
+    contain it at all then a warning is issued.  The warn_type and
+    the warn_name arguments are used as the name and the type of the
+    field when issuing the warning.
+
+  @return
+    converted value. 0 on error and on zero-dates -- check 'failure'
+*/
+static ulonglong get_date_from_str(THD *thd, String *str, 
+                                   timestamp_type warn_type, 
+                                   const char *warn_name, bool *error_arg)
+{
+  MYSQL_TIME l_time;
+  *error_arg= get_mysql_time_from_str(thd, str, warn_type, warn_name, &l_time);
+
+  if (*error_arg)
+    return 0;
+  return TIME_to_ulonglong_datetime(&l_time);
+}
+
+
 /*
   Check whether compare_datetime() can be used to compare items.
 

sql/item_cmpfunc.h

@@ -1721,3 +1721,6 @@ inline Item *and_conds(Item *a, Item *b)
 }
 
 Item *and_expressions(Item *a, Item *b, Item **org_item);
+
+bool get_mysql_time_from_str(THD *thd, String *str, timestamp_type warn_type, 
+                             const char *warn_name, MYSQL_TIME *l_time);

sql/opt_range.cc

@@ -5954,7 +5954,7 @@ get_mm_leaf(RANGE_OPT_PARAM *param, COND *conf_func, Field *field,
 
   switch (type) {
   case Item_func::LT_FUNC:
-    if (stored_field_cmp_to_item(field,value) == 0)
+    if (stored_field_cmp_to_item(param->thd, field, value) == 0)
       tree->max_flag=NEAR_MAX;
     /* fall through */
   case Item_func::LE_FUNC:
@@ -5969,14 +5969,14 @@ get_mm_leaf(RANGE_OPT_PARAM *param, COND *conf_func, Field *field,
   case Item_func::GT_FUNC:
     /* Don't use open ranges for partial key_segments */
     if ((!(key_part->flag & HA_PART_KEY_SEG)) &&
-        (stored_field_cmp_to_item(field, value) <= 0))
+        (stored_field_cmp_to_item(param->thd, field, value) <= 0))
       tree->min_flag=NEAR_MIN;
     tree->max_flag= NO_MAX_RANGE;
     break;
   case Item_func::GE_FUNC:
     /* Don't use open ranges for partial key_segments */
     if ((!(key_part->flag & HA_PART_KEY_SEG)) &&
-        (stored_field_cmp_to_item(field,value) < 0))
+        (stored_field_cmp_to_item(param->thd, field, value) < 0))
       tree->min_flag= NEAR_MIN;
     tree->max_flag=NO_MAX_RANGE;
     break;

sql/time.cc

@@ -965,20 +965,22 @@ calc_time_diff(MYSQL_TIME *l_time1, MYSQL_TIME *l_time2, int l_sign, longlong *s
     0   - a == b
     1   - a > b
 
-  NOTES
-    TIME.second_part is not considered during comparison
 */
 
-int
-my_time_compare(MYSQL_TIME *a, MYSQL_TIME *b)
+int my_time_compare(MYSQL_TIME *a, MYSQL_TIME *b)
 {
-  my_ulonglong a_t= TIME_to_ulonglong_datetime(a);
-  my_ulonglong b_t= TIME_to_ulonglong_datetime(b);
+  ulonglong a_t= TIME_to_ulonglong_datetime(a);
+  ulonglong b_t= TIME_to_ulonglong_datetime(b);
 
+  if (a_t < b_t)
+    return -1;
   if (a_t > b_t)
     return 1;
-  else if (a_t < b_t)
+
+  if (a->second_part < b->second_part)
     return -1;
+  if (a->second_part > b->second_part)
+    return 1;
 
   return 0;
 }