MDEV-8793 Wrong result set for SELECT ...

          WHERE COALESCE(time_column)=TIME('00:00:00')
            AND COALESCE(time_column)=DATE('2015-09-11')
MDEV-8814 Wrong result for WHERE datetime_column > TIME('00:00:00')

mysql-test/r/func_time.result

@@ -1824,8 +1824,6 @@ create table t1 (f1 datetime, key (f1));
 insert into t1 values ('2000-09-12 00:00:00'), ('2007-04-25 05:08:49');
 select * from t1 where f1 > time('-23:00:06');
 f1
-2000-09-12 00:00:00
-2007-04-25 05:08:49
 drop table t1;
 select maketime(20,61,10)+0;
 maketime(20,61,10)+0

mysql-test/r/type_time.result

@@ -969,5 +969,189 @@ Warnings:
 Note	1003	select `test`.`t1`.`a` AS `a` from `test`.`t1` where (coalesce(`test`.`t1`.`a`) = TIME'00:00:01')
 DROP TABLE t1;
 #
+# MDEV-8793 Wrong result set for SELECT ... WHERE COALESCE(time_column)=TIME('00:00:00') AND COALESCE(time_column)=DATE('2015-09-11')
+#
+SET timestamp=UNIX_TIMESTAMP('2015-09-11 20:20:20');
+CREATE TABLE t1 (a TIME);
+INSERT INTO t1 VALUES('10:20:30'),('00:00:00');
+SELECT * FROM t1 WHERE COALESCE(a)=TIME('00:00:00');
+a
+00:00:00
+SELECT * FROM t1 WHERE COALESCE(a)=DATE('2015-09-11');
+a
+00:00:00
+# TIME cast + DATE cast
+SELECT * FROM t1 WHERE COALESCE(a)=TIME('00:00:00') AND COALESCE(a)=DATE('2015-09-11');
+a
+00:00:00
+EXPLAIN EXTENDED
+SELECT * FROM t1 WHERE COALESCE(a)=TIME('00:00:00') AND COALESCE(a)=DATE('2015-09-11');
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	2	100.00	Using where
+Warnings:
+Note	1003	select `test`.`t1`.`a` AS `a` from `test`.`t1` where (coalesce(`test`.`t1`.`a`) = <cache>(00:00:00))
+# TIME cast + DATE literal
+SELECT * FROM t1 WHERE COALESCE(a)=TIME('00:00:00') AND COALESCE(a)=DATE'2015-09-11';
+a
+00:00:00
+EXPLAIN EXTENDED
+SELECT * FROM t1 WHERE COALESCE(a)=TIME('00:00:00') AND COALESCE(a)=DATE'2015-09-11';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	2	100.00	Using where
+Warnings:
+Note	1003	select `test`.`t1`.`a` AS `a` from `test`.`t1` where (coalesce(`test`.`t1`.`a`) = <cache>(00:00:00))
+# TIME literal + DATE cast
+SELECT * FROM t1 WHERE COALESCE(a)=TIME'00:00:00' AND COALESCE(a)=DATE('2015-09-11');
+a
+00:00:00
+EXPLAIN EXTENDED
+SELECT * FROM t1 WHERE COALESCE(a)=TIME'00:00:00' AND COALESCE(a)=DATE('2015-09-11');
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	2	100.00	Using where
+Warnings:
+Note	1003	select `test`.`t1`.`a` AS `a` from `test`.`t1` where (coalesce(`test`.`t1`.`a`) = TIME'00:00:00')
+# TIME literal + DATE literal
+SELECT * FROM t1 WHERE COALESCE(a)=TIME'00:00:00' AND COALESCE(a)=DATE'2015-09-11';
+a
+00:00:00
+EXPLAIN EXTENDED
+SELECT * FROM t1 WHERE COALESCE(a)=TIME'00:00:00' AND COALESCE(a)=DATE'2015-09-11';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	2	100.00	Using where
+Warnings:
+Note	1003	select `test`.`t1`.`a` AS `a` from `test`.`t1` where (coalesce(`test`.`t1`.`a`) = TIME'00:00:00')
+# TIME-alike string literal + DATE cast
+SELECT * FROM t1 WHERE COALESCE(a)='00:00:00' AND COALESCE(a)=DATE('2015-09-11');
+a
+00:00:00
+EXPLAIN EXTENDED
+SELECT * FROM t1 WHERE COALESCE(a)='00:00:00' AND COALESCE(a)=DATE('2015-09-11');
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	2	100.00	Using where
+Warnings:
+Note	1003	select `test`.`t1`.`a` AS `a` from `test`.`t1` where ((coalesce(`test`.`t1`.`a`) = '00:00:00') and (coalesce(`test`.`t1`.`a`) = <cache>(2015-09-11 00:00:00)))
+# TIME-alike string literal + DATE literal
+SELECT * FROM t1 WHERE COALESCE(a)='00:00:00' AND COALESCE(a)=DATE'2015-09-11';
+a
+00:00:00
+EXPLAIN EXTENDED
+SELECT * FROM t1 WHERE COALESCE(a)='00:00:00' AND COALESCE(a)=DATE'2015-09-11';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	2	100.00	Using where
+Warnings:
+Note	1003	select `test`.`t1`.`a` AS `a` from `test`.`t1` where ((coalesce(`test`.`t1`.`a`) = '00:00:00') and (coalesce(`test`.`t1`.`a`) = DATE'2015-09-11'))
+# TIME-alike integer literal + DATE cast
+SELECT * FROM t1 WHERE COALESCE(a)=0 AND COALESCE(a)=DATE('2015-09-11');
+a
+00:00:00
+EXPLAIN EXTENDED
+SELECT * FROM t1 WHERE COALESCE(a)=0 AND COALESCE(a)=DATE('2015-09-11');
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	2	100.00	Using where
+Warnings:
+Note	1003	select `test`.`t1`.`a` AS `a` from `test`.`t1` where ((coalesce(`test`.`t1`.`a`) = 0) and (coalesce(`test`.`t1`.`a`) = <cache>(2015-09-11 00:00:00)))
+# TIME-alike integer literal + DATE literal
+SELECT * FROM t1 WHERE COALESCE(a)=0 AND COALESCE(a)=DATE'2015-09-11';
+a
+00:00:00
+EXPLAIN EXTENDED
+SELECT * FROM t1 WHERE COALESCE(a)=0 AND COALESCE(a)=DATE'2015-09-11';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	2	100.00	Using where
+Warnings:
+Note	1003	select `test`.`t1`.`a` AS `a` from `test`.`t1` where ((coalesce(`test`.`t1`.`a`) = 0) and (coalesce(`test`.`t1`.`a`) = DATE'2015-09-11'))
+# DATE cast + TIME cast
+SELECT * FROM t1 WHERE COALESCE(a)=DATE('2015-09-11') AND COALESCE(a)=TIME('00:00:00');
+a
+00:00:00
+EXPLAIN EXTENDED
+SELECT * FROM t1 WHERE COALESCE(a)=DATE('2015-09-11') AND COALESCE(a)=TIME('00:00:00');
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	2	100.00	Using where
+Warnings:
+Note	1003	select `test`.`t1`.`a` AS `a` from `test`.`t1` where (coalesce(`test`.`t1`.`a`) = <cache>(2015-09-11 00:00:00))
+# DATE cast + TIME literal
+SELECT * FROM t1 WHERE COALESCE(a)=DATE('2015-09-11') AND COALESCE(a)=TIME'00:00:00';
+a
+00:00:00
+EXPLAIN EXTENDED
+SELECT * FROM t1 WHERE COALESCE(a)=DATE('2015-09-11') AND COALESCE(a)=TIME'00:00:00';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	2	100.00	Using where
+Warnings:
+Note	1003	select `test`.`t1`.`a` AS `a` from `test`.`t1` where (coalesce(`test`.`t1`.`a`) = <cache>(2015-09-11 00:00:00))
+# DATE cast + TIME-alike string literal
+SELECT * FROM t1 WHERE COALESCE(a)=DATE('2015-09-11') AND COALESCE(a)='00:00:00';
+a
+00:00:00
+EXPLAIN EXTENDED
+SELECT * FROM t1 WHERE COALESCE(a)=DATE('2015-09-11') AND COALESCE(a)='00:00:00';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	2	100.00	Using where
+Warnings:
+Note	1003	select `test`.`t1`.`a` AS `a` from `test`.`t1` where ((coalesce(`test`.`t1`.`a`) = <cache>(2015-09-11 00:00:00)) and (coalesce(`test`.`t1`.`a`) = '00:00:00'))
+# DATE cast + TIME-alike integer literal
+SELECT * FROM t1 WHERE COALESCE(a)=DATE('2015-09-11') AND COALESCE(a)=0;
+a
+00:00:00
+EXPLAIN EXTENDED
+SELECT * FROM t1 WHERE COALESCE(a)=DATE('2015-09-11') AND COALESCE(a)=0;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	2	100.00	Using where
+Warnings:
+Note	1003	select `test`.`t1`.`a` AS `a` from `test`.`t1` where ((coalesce(`test`.`t1`.`a`) = <cache>(2015-09-11 00:00:00)) and (coalesce(`test`.`t1`.`a`) = 0))
+# DATE literal + TIME cast
+SELECT * FROM t1 WHERE COALESCE(a)=DATE'2015-09-11' AND COALESCE(a)=TIME('00:00:00');
+a
+00:00:00
+EXPLAIN EXTENDED
+SELECT * FROM t1 WHERE COALESCE(a)=DATE'2015-09-11' AND COALESCE(a)=TIME('00:00:00');
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	2	100.00	Using where
+Warnings:
+Note	1003	select `test`.`t1`.`a` AS `a` from `test`.`t1` where (coalesce(`test`.`t1`.`a`) = DATE'2015-09-11')
+# DATE literal + TIME literal
+SELECT * FROM t1 WHERE COALESCE(a)=DATE'2015-09-11' AND COALESCE(a)=TIME'00:00:00';
+a
+00:00:00
+EXPLAIN EXTENDED
+SELECT * FROM t1 WHERE COALESCE(a)=DATE'2015-09-11' AND COALESCE(a)=TIME'00:00:00';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	2	100.00	Using where
+Warnings:
+Note	1003	select `test`.`t1`.`a` AS `a` from `test`.`t1` where (coalesce(`test`.`t1`.`a`) = DATE'2015-09-11')
+# DATE literal + TIME-alike string literal
+SELECT * FROM t1 WHERE COALESCE(a)=DATE'2015-09-11' AND COALESCE(a)='00:00:00';
+a
+00:00:00
+EXPLAIN EXTENDED
+SELECT * FROM t1 WHERE COALESCE(a)=DATE'2015-09-11' AND COALESCE(a)='00:00:00';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	2	100.00	Using where
+Warnings:
+Note	1003	select `test`.`t1`.`a` AS `a` from `test`.`t1` where ((coalesce(`test`.`t1`.`a`) = DATE'2015-09-11') and (coalesce(`test`.`t1`.`a`) = '00:00:00'))
+# DATE literal + TIME-alike integer literal
+SELECT * FROM t1 WHERE COALESCE(a)=DATE'2015-09-11' AND COALESCE(a)=0;
+a
+00:00:00
+EXPLAIN EXTENDED
+SELECT * FROM t1 WHERE COALESCE(a)=DATE'2015-09-11' AND COALESCE(a)=0;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	2	100.00	Using where
+Warnings:
+Note	1003	select `test`.`t1`.`a` AS `a` from `test`.`t1` where ((coalesce(`test`.`t1`.`a`) = DATE'2015-09-11') and (coalesce(`test`.`t1`.`a`) = 0))
+DROP TABLE t1;
+SET timestamp=DEFAULT;
+#
+# MDEV-8814 Wrong result for WHERE datetime_column > TIME('00:00:00')
+#
+CREATE TABLE t1 (a DATETIME);
+INSERT INTO t1 VALUES ('2000-09-12 00:00:00'), ('2007-04-25 05:08:49');
+SELECT * FROM t1 WHERE a>TIME'00:00:00';
+a
+SELECT * FROM t1 WHERE a>TIME('00:00:00');
+a
+DROP TABLE t1;
+#
 # End of 10.1 tests
 #

mysql-test/t/type_time.test

@@ -584,6 +584,110 @@ INSERT INTO t1 VALUES ('00:00:01'),('00:00:02');
 EXPLAIN EXTENDED SELECT * FROM t1 WHERE COALESCE(a)=TIME'00:00:01' AND COALESCE(a)>=TIME'00:00:01';
 DROP TABLE t1;
 
+--echo #
+--echo # MDEV-8793 Wrong result set for SELECT ... WHERE COALESCE(time_column)=TIME('00:00:00') AND COALESCE(time_column)=DATE('2015-09-11')
+--echo #
+SET timestamp=UNIX_TIMESTAMP('2015-09-11 20:20:20');
+CREATE TABLE t1 (a TIME);
+INSERT INTO t1 VALUES('10:20:30'),('00:00:00');
+SELECT * FROM t1 WHERE COALESCE(a)=TIME('00:00:00');
+SELECT * FROM t1 WHERE COALESCE(a)=DATE('2015-09-11');
+
+--echo # TIME cast + DATE cast
+SELECT * FROM t1 WHERE COALESCE(a)=TIME('00:00:00') AND COALESCE(a)=DATE('2015-09-11');
+EXPLAIN EXTENDED
+SELECT * FROM t1 WHERE COALESCE(a)=TIME('00:00:00') AND COALESCE(a)=DATE('2015-09-11');
+
+--echo # TIME cast + DATE literal
+SELECT * FROM t1 WHERE COALESCE(a)=TIME('00:00:00') AND COALESCE(a)=DATE'2015-09-11';
+EXPLAIN EXTENDED
+SELECT * FROM t1 WHERE COALESCE(a)=TIME('00:00:00') AND COALESCE(a)=DATE'2015-09-11';
+
+--echo # TIME literal + DATE cast
+SELECT * FROM t1 WHERE COALESCE(a)=TIME'00:00:00' AND COALESCE(a)=DATE('2015-09-11');
+EXPLAIN EXTENDED
+SELECT * FROM t1 WHERE COALESCE(a)=TIME'00:00:00' AND COALESCE(a)=DATE('2015-09-11');
+
+--echo # TIME literal + DATE literal
+SELECT * FROM t1 WHERE COALESCE(a)=TIME'00:00:00' AND COALESCE(a)=DATE'2015-09-11';
+EXPLAIN EXTENDED
+SELECT * FROM t1 WHERE COALESCE(a)=TIME'00:00:00' AND COALESCE(a)=DATE'2015-09-11';
+
+--echo # TIME-alike string literal + DATE cast
+SELECT * FROM t1 WHERE COALESCE(a)='00:00:00' AND COALESCE(a)=DATE('2015-09-11');
+EXPLAIN EXTENDED
+SELECT * FROM t1 WHERE COALESCE(a)='00:00:00' AND COALESCE(a)=DATE('2015-09-11');
+
+--echo # TIME-alike string literal + DATE literal
+SELECT * FROM t1 WHERE COALESCE(a)='00:00:00' AND COALESCE(a)=DATE'2015-09-11';
+EXPLAIN EXTENDED
+SELECT * FROM t1 WHERE COALESCE(a)='00:00:00' AND COALESCE(a)=DATE'2015-09-11';
+
+--echo # TIME-alike integer literal + DATE cast
+SELECT * FROM t1 WHERE COALESCE(a)=0 AND COALESCE(a)=DATE('2015-09-11');
+EXPLAIN EXTENDED
+SELECT * FROM t1 WHERE COALESCE(a)=0 AND COALESCE(a)=DATE('2015-09-11');
+
+--echo # TIME-alike integer literal + DATE literal
+SELECT * FROM t1 WHERE COALESCE(a)=0 AND COALESCE(a)=DATE'2015-09-11';
+EXPLAIN EXTENDED
+SELECT * FROM t1 WHERE COALESCE(a)=0 AND COALESCE(a)=DATE'2015-09-11';
+
+
+### Now test the opposite order of the two equality expressions
+
+--echo # DATE cast + TIME cast
+SELECT * FROM t1 WHERE COALESCE(a)=DATE('2015-09-11') AND COALESCE(a)=TIME('00:00:00');
+EXPLAIN EXTENDED
+SELECT * FROM t1 WHERE COALESCE(a)=DATE('2015-09-11') AND COALESCE(a)=TIME('00:00:00');
+
+--echo # DATE cast + TIME literal
+SELECT * FROM t1 WHERE COALESCE(a)=DATE('2015-09-11') AND COALESCE(a)=TIME'00:00:00';
+EXPLAIN EXTENDED
+SELECT * FROM t1 WHERE COALESCE(a)=DATE('2015-09-11') AND COALESCE(a)=TIME'00:00:00';
+
+--echo # DATE cast + TIME-alike string literal
+SELECT * FROM t1 WHERE COALESCE(a)=DATE('2015-09-11') AND COALESCE(a)='00:00:00';
+EXPLAIN EXTENDED
+SELECT * FROM t1 WHERE COALESCE(a)=DATE('2015-09-11') AND COALESCE(a)='00:00:00';
+
+--echo # DATE cast + TIME-alike integer literal
+SELECT * FROM t1 WHERE COALESCE(a)=DATE('2015-09-11') AND COALESCE(a)=0;
+EXPLAIN EXTENDED
+SELECT * FROM t1 WHERE COALESCE(a)=DATE('2015-09-11') AND COALESCE(a)=0;
+
+--echo # DATE literal + TIME cast
+SELECT * FROM t1 WHERE COALESCE(a)=DATE'2015-09-11' AND COALESCE(a)=TIME('00:00:00');
+EXPLAIN EXTENDED
+SELECT * FROM t1 WHERE COALESCE(a)=DATE'2015-09-11' AND COALESCE(a)=TIME('00:00:00');
+
+--echo # DATE literal + TIME literal
+SELECT * FROM t1 WHERE COALESCE(a)=DATE'2015-09-11' AND COALESCE(a)=TIME'00:00:00';
+EXPLAIN EXTENDED
+SELECT * FROM t1 WHERE COALESCE(a)=DATE'2015-09-11' AND COALESCE(a)=TIME'00:00:00';
+
+--echo # DATE literal + TIME-alike string literal
+SELECT * FROM t1 WHERE COALESCE(a)=DATE'2015-09-11' AND COALESCE(a)='00:00:00';
+EXPLAIN EXTENDED
+SELECT * FROM t1 WHERE COALESCE(a)=DATE'2015-09-11' AND COALESCE(a)='00:00:00';
+
+--echo # DATE literal + TIME-alike integer literal
+SELECT * FROM t1 WHERE COALESCE(a)=DATE'2015-09-11' AND COALESCE(a)=0;
+EXPLAIN EXTENDED
+SELECT * FROM t1 WHERE COALESCE(a)=DATE'2015-09-11' AND COALESCE(a)=0;
+
+DROP TABLE t1;
+SET timestamp=DEFAULT;
+
+--echo #
+--echo # MDEV-8814 Wrong result for WHERE datetime_column > TIME('00:00:00')
+--echo #
+CREATE TABLE t1 (a DATETIME);
+INSERT INTO t1 VALUES ('2000-09-12 00:00:00'), ('2007-04-25 05:08:49');
+SELECT * FROM t1 WHERE a>TIME'00:00:00';
+SELECT * FROM t1 WHERE a>TIME('00:00:00');
+DROP TABLE t1;
+
 --echo #
 --echo # End of 10.1 tests
 --echo #

sql/item.cc

@@ -8596,7 +8596,8 @@ void resolve_const_item(THD *thd, Item **ref, Item *comp_item)
     bool is_null;
     Item **ref_copy= ref;
     /* the following call creates a constant and puts it in new_item */
-    get_datetime_value(thd, &ref_copy, &new_item, comp_item, &is_null);
+    enum_field_types type= item->field_type_for_temporal_comparison(comp_item);
+    get_datetime_value(thd, &ref_copy, &new_item, type, &is_null);
     if (is_null)
       new_item= new (mem_root) Item_null(thd, name);
     break;
@@ -8936,9 +8937,25 @@ Item_cache_temporal::Item_cache_temporal(THD *thd,
 }
 
 
-longlong Item_cache_temporal::val_temporal_packed()
+longlong Item_cache_temporal::val_datetime_packed()
 {
   DBUG_ASSERT(fixed == 1);
+  if (Item_cache_temporal::field_type() == MYSQL_TYPE_TIME)
+    return Item::val_datetime_packed(); // TIME-to-DATETIME conversion needed
+  if ((!value_cached && !cache_value()) || null_value)
+  {
+    null_value= TRUE;
+    return 0;
+  }
+  return value;
+}
+
+
+longlong Item_cache_temporal::val_time_packed()
+{
+  DBUG_ASSERT(fixed == 1);
+  if (Item_cache_temporal::field_type() != MYSQL_TYPE_TIME)
+    return Item::val_time_packed(); // DATETIME-to-TIME conversion needed
   if ((!value_cached && !cache_value()) || null_value)
   {
     null_value= TRUE;

sql/item.h

@@ -1221,6 +1221,48 @@ public:
   */
   bool get_time_with_conversion(THD *thd, MYSQL_TIME *ltime,
                                 ulonglong fuzzydate);
+  // Get a DATE or DATETIME value in numeric packed format for comparison
+  virtual longlong val_datetime_packed()
+  {
+    MYSQL_TIME ltime;
+    uint fuzzydate= TIME_FUZZY_DATES | TIME_INVALID_DATES;
+    return get_date_with_conversion(&ltime, fuzzydate) ? 0 : pack_time(&ltime);
+  }
+  // Get a TIME value in numeric packed format for comparison
+  virtual longlong val_time_packed()
+  {
+    MYSQL_TIME ltime;
+    uint fuzzydate= TIME_FUZZY_DATES | TIME_INVALID_DATES | TIME_TIME_ONLY;
+    return get_date(&ltime, fuzzydate) ? 0 : pack_time(&ltime);
+  }
+  // Get a temporal value in packed DATE/DATETIME or TIME format
+  longlong val_temporal_packed(enum_field_types f_type)
+  {
+    return f_type == MYSQL_TYPE_TIME ? val_time_packed() :
+                                       val_datetime_packed();
+  }
+  enum_field_types field_type_for_temporal_comparison(const Item *other) const
+  {
+    if (cmp_type() == TIME_RESULT)
+    {
+      if (other->cmp_type() == TIME_RESULT)
+        return Field::field_type_merge(field_type(), other->field_type());
+      else
+        return field_type();
+    }
+    else
+    {
+      if (other->cmp_type() == TIME_RESULT)
+        return other->field_type();
+      DBUG_ASSERT(0); // Two non-temporal data types, we should not get to here
+      return MYSQL_TYPE_DATETIME;
+    }
+  }
+  // Get a temporal value to compare to another Item
+  longlong val_temporal_packed(const Item *other)
+  {
+    return val_temporal_packed(field_type_for_temporal_comparison(other));
+  }
   bool get_seconds(ulonglong *sec, ulong *sec_part);
   virtual bool get_date_result(MYSQL_TIME *ltime, ulonglong fuzzydate)
   { return get_date(ltime,fuzzydate); }
@@ -4898,7 +4940,8 @@ public:
   String* val_str(String *str);
   my_decimal *val_decimal(my_decimal *);
   longlong val_int();
-  longlong val_temporal_packed();
+  longlong val_datetime_packed();
+  longlong val_time_packed();
   double val_real();
   bool cache_value();
   bool get_date(MYSQL_TIME *ltime, ulonglong fuzzydate);

sql/item_cmpfunc.h

@@ -58,12 +58,12 @@ class Arg_comparator: public Sql_alloc
   Item *a_cache, *b_cache;         // Cached values of a and b items
                                    //   when one of arguments is NULL.
   int set_compare_func(Item_func_or_sum *owner, Item_result type);
-  inline int set_compare_func(Item_func_or_sum *owner_arg)
-  {
-    return set_compare_func(owner_arg, item_cmp_type(*a, *b));
-  }
+  int set_cmp_func(Item_func_or_sum *owner_arg, Item **a1, Item **a2);
   bool agg_arg_charsets_for_comparison();
 
+  int compare_temporal(enum_field_types type);
+  int compare_e_temporal(enum_field_types type);
+
 public:
   DTCollation cmp_collation;
   /* Allow owner function to use string buffers. */
@@ -76,20 +76,12 @@ public:
     m_compare_type(STRING_RESULT), set_null(TRUE),
     comparators(0), thd(0), a_cache(0), b_cache(0) {};
 
-private:
-  int set_cmp_func(Item_func_or_sum *owner_arg,
-			  Item **a1, Item **a2,
-			  Item_result type);
 public:
-  void set_compare_type(Item_result type)
-  {
-    m_compare_type= type;
-  }
   inline int set_cmp_func(Item_func_or_sum *owner_arg,
 			  Item **a1, Item **a2, bool set_null_arg)
   {
     set_null= set_null_arg;
-    return set_cmp_func(owner_arg, a1, a2, item_cmp_type(*a1, *a2));
+    return set_cmp_func(owner_arg, a1, a2);
   }
   inline int compare() { return (this->*func)(); }
 
@@ -111,13 +103,13 @@ public:
   int compare_e_row();           // compare args[0] & args[1]
   int compare_real_fixed();
   int compare_e_real_fixed();
-  int compare_datetime();        // compare args[0] & args[1] as DATETIMEs
-  int compare_e_datetime();
+  int compare_datetime()   { return compare_temporal(MYSQL_TYPE_DATETIME); }
+  int compare_e_datetime() { return compare_e_temporal(MYSQL_TYPE_DATETIME); }
+  int compare_time()       { return compare_temporal(MYSQL_TYPE_TIME); }
+  int compare_e_time()     { return compare_e_temporal(MYSQL_TYPE_TIME); }
 
   Item** cache_converted_constant(THD *thd, Item **value, Item **cache,
                                   Item_result type);
-  void set_datetime_cmp_func(Item_func_or_sum *owner_arg,
-                             Item **a1, Item **b1);
   static arg_cmp_func comparator_matrix [6][2];
   inline bool is_owner_equal_func()
   {
@@ -2052,12 +2044,6 @@ class Item_equal: public Item_bool_func
     the equal_items should be ignored.
   */
   bool cond_true;
-  /* 
-    The comparator used to compare constants equal to fields from equal_items
-    as datetimes. The comparator is used only if compare_as_dates=TRUE
-  */
-  Arg_comparator cmp;
- 
   /*
     For Item_equal objects inside an OR clause: one of the fields that were
     used in the original equality.
@@ -2066,6 +2052,9 @@ class Item_equal: public Item_bool_func
 
   bool link_equal_fields;
 
+  Item_result m_compare_type;
+  CHARSET_INFO *m_compare_collation;
+  String cmp_value1, cmp_value2;
 public:
 
   COND_EQUAL *upper_levels;       /* multiple equalities of upper and levels */
@@ -2103,9 +2092,8 @@ public:
   bool walk(Item_processor processor, bool walk_subquery, uchar *arg);
   Item *transform(THD *thd, Item_transformer transformer, uchar *arg);
   virtual void print(String *str, enum_query_type query_type);
-  Item_result compare_type() const { return cmp.compare_type(); }
-  CHARSET_INFO *compare_collation() const
-  { return cmp.cmp_collation.collation; }
+  Item_result compare_type() const { return m_compare_type; }
+  CHARSET_INFO *compare_collation() const { return m_compare_collation; }
 
   void set_context_field(Item_field *ctx_field) { context_field= ctx_field; }
   void set_link_equal_fields(bool flag) { link_equal_fields= flag; }
@@ -2309,7 +2297,7 @@ inline bool is_cond_or(Item *item)
 Item *and_expressions(Item *a, Item *b, Item **org_item);
 
 longlong get_datetime_value(THD *thd, Item ***item_arg, Item **cache_arg,
-                            Item *warn_item, bool *is_null);
+                            enum_field_types f_type, bool *is_null);
 
 
 bool get_mysql_time_from_str(THD *thd, String *str, timestamp_type warn_type,

sql/item_func.cc

@@ -2910,10 +2910,7 @@ bool Item_func_min_max::get_date(MYSQL_TIME *ltime, ulonglong fuzzy_date)
 
   for (uint i=0; i < arg_count ; i++)
   {
-    Item **arg= args + i;
-    bool is_null_tmp;
-    longlong res= get_datetime_value(thd, &arg, 0, compare_as_dates,
-                                     &is_null_tmp);
+    longlong res= args[i]->val_temporal_packed(compare_as_dates);
 
     /* Check if we need to stop (because of error or KILL) and stop the loop */
     if (thd->is_error() || args[i]->null_value)

sql/sql_select.cc

@@ -13932,6 +13932,29 @@ can_change_cond_ref_to_const(Item_bool_func2 *target,
       target->compare_collation() == source->compare_collation() &&
       target_value->collation.collation == source_const->collation.collation;
   }
+  if (target->compare_type() == TIME_RESULT)
+  {
+    if (target_value->cmp_type() != TIME_RESULT)
+    {
+      /*
+        Can't rewrite:
+          WHERE COALESCE(time_column)='00:00:00'
+            AND COALESCE(time_column)=DATE'2015-09-11'
+        to
+          WHERE DATE'2015-09-11'='00:00:00'
+            AND COALESCE(time_column)=DATE'2015-09-11'
+        because the left part will erroneously try to parse '00:00:00'
+        as DATE, not as TIME.
+
+        TODO: It could still be rewritten to:
+          WHERE DATE'2015-09-11'=TIME'00:00:00'
+            AND COALESCE(time_column)=DATE'2015-09-11'
+        i.e. we need to replace both target_expr and target_value
+        at the same time. This is not supported yet.
+      */
+      return false;
+    }
+  }
   return true; // Non-string comparison
 }