Bug#27216: functions with parameters of different date types may return wrong

type of the result.

There are several functions that accept parameters of different types.
The result field type of such functions was determined based on
the aggregated result type of its arguments. As the DATE and the DATETIME
types are represented by the STRING type, the result field type
of the affected functions was always STRING for DATE/DATETIME arguments.
The affected functions are COALESCE, IF, IFNULL, CASE, LEAST/GREATEST, CASE.

Now the affected functions aggregate the field types of their arguments rather
than their result types and return the result of aggregation as their result
field type.
The cached_field_type member variable is added to the number of classes to
hold the aggregated result field type.
The str_to_date() function's result field type now defaults to the
MYSQL_TYPE_DATETIME.
The agg_field_type() function is added. It aggregates field types with help
of the Field::field_type_merge() function.
The create_table_from_items() function now uses the 
item->tmp_table_field_from_field_type() function to get the proper field
when the item is a function with a STRING result type.

libmysql/libmysql.c

@@ -4355,6 +4355,7 @@ static my_bool setup_one_fetch_function(MYSQL_BIND *param, MYSQL_FIELD *field)
   case MYSQL_TYPE_STRING:
   case MYSQL_TYPE_DECIMAL:
   case MYSQL_TYPE_NEWDECIMAL:
+  case MYSQL_TYPE_NEWDATE:
     DBUG_ASSERT(param->buffer_length != 0);
     param->fetch_result= fetch_result_str;
     break;
@@ -4427,6 +4428,7 @@ static my_bool setup_one_fetch_function(MYSQL_BIND *param, MYSQL_FIELD *field)
   case MYSQL_TYPE_VAR_STRING:
   case MYSQL_TYPE_STRING:
   case MYSQL_TYPE_BIT:
+  case MYSQL_TYPE_NEWDATE:
     param->skip_result= skip_result_string;
     break;
   default:

mysql-test/r/date_formats.result

@@ -481,7 +481,7 @@ str_to_date(a,b)
 create table t2 select str_to_date(a,b) from t1;
 describe t2;
 Field	Type	Null	Key	Default	Extra
-str_to_date(a,b)	binary(29)	YES		NULL	
+str_to_date(a,b)	datetime	YES		NULL	
 select str_to_date("2003-01-02 10:11:12.0012", "%Y-%m-%d %H:%i:%S.%f") as f1,
 str_to_date("2003-01-02 10:11:12.0012", "%Y-%m-%d %H:%i:%S") as f2,
 str_to_date("2003-01-02", "%Y-%m-%d") as f3,

mysql-test/r/type_datetime.result

@@ -427,3 +427,64 @@ f1
 Warnings:
 Warning	1292	Incorrect datetime value: '2007010100000' for column 'f1' at row 1
 drop table t1;
+#
+# Bug#27216: functions with parameters of different date types may
+#            return wrong type of the result.
+#
+create table t1 (f1 date, f2 datetime, f3 varchar(20));
+create table t2 as select coalesce(f1,f1) as f4 from t1;
+desc t2;
+Field	Type	Null	Key	Default	Extra
+f4	date	YES		NULL	
+create table t3 as select coalesce(f1,f2) as f4 from t1;
+desc t3;
+Field	Type	Null	Key	Default	Extra
+f4	datetime	YES		NULL	
+create table t4 as select coalesce(f2,f2) as f4 from t1;
+desc t4;
+Field	Type	Null	Key	Default	Extra
+f4	datetime	YES		NULL	
+create table t5 as select coalesce(f1,f3) as f4 from t1;
+desc t5;
+Field	Type	Null	Key	Default	Extra
+f4	varbinary(20)	YES		NULL	
+create table t6 as select coalesce(f2,f3) as f4 from t1;
+desc t6;
+Field	Type	Null	Key	Default	Extra
+f4	varbinary(20)	YES		NULL	
+create table t7 as select coalesce(makedate(1997,1),f2) as f4 from t1;
+desc t7;
+Field	Type	Null	Key	Default	Extra
+f4	datetime	YES		NULL	
+create table t8 as select coalesce(cast('01-01-01' as datetime),f2) as f4
+from t1;
+desc t8;
+Field	Type	Null	Key	Default	Extra
+f4	datetime	YES		NULL	
+create table t9 as select case when 1 then cast('01-01-01' as date)
+when 0 then cast('01-01-01' as date) end as f4 from t1;
+desc t9;
+Field	Type	Null	Key	Default	Extra
+f4	date	YES		NULL	
+create table t10 as select case when 1 then cast('01-01-01' as datetime)
+when 0 then cast('01-01-01' as datetime) end as f4 from t1;
+desc t10;
+Field	Type	Null	Key	Default	Extra
+f4	datetime	YES		NULL	
+create table t11 as select if(1, cast('01-01-01' as datetime),
+cast('01-01-01' as date)) as f4 from t1;
+desc t11;
+Field	Type	Null	Key	Default	Extra
+f4	datetime	YES		NULL	
+create table t12 as select least(cast('01-01-01' as datetime),
+cast('01-01-01' as date)) as f4 from t1;
+desc t12;
+Field	Type	Null	Key	Default	Extra
+f4	datetime	YES		NULL	
+create table t13 as select ifnull(cast('01-01-01' as datetime),
+cast('01-01-01' as date)) as f4 from t1;
+desc t13;
+Field	Type	Null	Key	Default	Extra
+f4	datetime	YES		NULL	
+drop tables t1,t2,t3,t4,t5,t6,t7,t8,t9,t10,t11,t12,t13;
+###################################################################

mysql-test/t/type_datetime.test

@@ -282,3 +282,41 @@ select * from t1 where f1 between 20020101 and 20070101000000;
 select * from t1 where f1 between 2002010 and 20070101000000;
 select * from t1 where f1 between 20020101 and 2007010100000;
 drop table t1;
+
+--echo #
+--echo # Bug#27216: functions with parameters of different date types may
+--echo #            return wrong type of the result.
+--echo #
+create table t1 (f1 date, f2 datetime, f3 varchar(20));
+create table t2 as select coalesce(f1,f1) as f4 from t1;
+desc t2;
+create table t3 as select coalesce(f1,f2) as f4 from t1;
+desc t3;
+create table t4 as select coalesce(f2,f2) as f4 from t1;
+desc t4;
+create table t5 as select coalesce(f1,f3) as f4 from t1;
+desc t5;
+create table t6 as select coalesce(f2,f3) as f4 from t1;
+desc t6;
+create table t7 as select coalesce(makedate(1997,1),f2) as f4 from t1;
+desc t7;
+create table t8 as select coalesce(cast('01-01-01' as datetime),f2) as f4
+  from t1;
+desc t8;
+create table t9 as select case when 1 then cast('01-01-01' as date)
+  when 0 then cast('01-01-01' as date) end as f4 from t1;
+desc t9;
+create table t10 as select case when 1 then cast('01-01-01' as datetime)
+  when 0 then cast('01-01-01' as datetime) end as f4 from t1;
+desc t10;
+create table t11 as select if(1, cast('01-01-01' as datetime),
+  cast('01-01-01' as date)) as f4 from t1;
+desc t11;
+create table t12 as select least(cast('01-01-01' as datetime),
+  cast('01-01-01' as date)) as f4 from t1;
+desc t12;
+create table t13 as select ifnull(cast('01-01-01' as datetime),
+  cast('01-01-01' as date)) as f4 from t1;
+desc t13;
+drop tables t1,t2,t3,t4,t5,t6,t7,t8,t9,t10,t11,t12,t13;
+--echo ###################################################################

sql/item_cmpfunc.cc

@@ -147,6 +147,36 @@ static int agg_cmp_type(THD *thd, Item_result *type, Item **items, uint nitems)
 }
 
 
+/**
+  @brief Aggregates field types from the array of items.
+
+  @param[in] items  array of items to aggregate the type from
+  @paran[in] nitems number of items in the array
+
+  @details This function aggregates field types from the array of items.
+    Found type is supposed to be used later as the result field type
+    of a multi-argument function.
+    Aggregation itself is performed by the Field::field_type_merge()
+    function.
+
+  @note The term "aggregation" is used here in the sense of inferring the
+    result type of a function from its argument types.
+
+  @return aggregated field type.
+*/
+
+enum_field_types agg_field_type(Item **items, uint nitems)
+{
+  uint i;
+  if (!nitems || items[0]->result_type() == ROW_RESULT )
+    return (enum_field_types)-1;
+  enum_field_types res= items[0]->field_type();
+  for (i= 1 ; i < nitems ; i++)
+    res= Field::field_type_merge(res, items[i]->field_type());
+  return res;
+}
+
+
 static void my_coll_agg_error(DTCollation &c1, DTCollation &c2,
                               const char *fname)
 {
@@ -2009,9 +2039,7 @@ Item_func_ifnull::fix_length_and_dec()
   default:
     DBUG_ASSERT(0);
   }
-  cached_field_type= args[0]->field_type();
-  if (cached_field_type != args[1]->field_type())
-    cached_field_type= Item_func::field_type();
+  cached_field_type= agg_field_type(args, 2);
 }
 
 
@@ -2159,11 +2187,13 @@ Item_func_if::fix_length_and_dec()
   {
     cached_result_type= arg2_type;
     collation.set(args[2]->collation.collation);
+    cached_field_type= args[2]->field_type();
   }
   else if (null2)
   {
     cached_result_type= arg1_type;
     collation.set(args[1]->collation.collation);
+    cached_field_type= args[1]->field_type();
   }
   else
   {
@@ -2177,6 +2207,7 @@ Item_func_if::fix_length_and_dec()
     {
       collation.set(&my_charset_bin);	// Number
     }
+    cached_field_type= agg_field_type(args + 1, 2);
   }
 
   if ((cached_result_type == DECIMAL_RESULT )
@@ -2556,7 +2587,7 @@ void Item_func_case::fix_length_and_dec()
       agg_arg_charsets(collation, agg, nagg, MY_COLL_ALLOW_CONV, 1))
     return;
   
-  
+  cached_field_type= agg_field_type(agg, nagg);
   /*
     Aggregate first expression and all THEN expression types
     and collations when string comparison
@@ -2695,6 +2726,7 @@ my_decimal *Item_func_coalesce::decimal_op(my_decimal *decimal_value)
 
 void Item_func_coalesce::fix_length_and_dec()
 {
+  cached_field_type= agg_field_type(args, arg_count);
   agg_result_type(&hybrid_type, args, arg_count);
   switch (hybrid_type) {
   case STRING_RESULT:

sql/item_cmpfunc.h

@@ -640,6 +640,7 @@ class Item_func_interval :public Item_int_func
 class Item_func_coalesce :public Item_func_numhybrid
 {
 protected:
+  enum_field_types cached_field_type;
   Item_func_coalesce(Item *a, Item *b) :Item_func_numhybrid(a, b) {}
 public:
   Item_func_coalesce(List<Item> &list) :Item_func_numhybrid(list) {}
@@ -652,13 +653,13 @@ class Item_func_coalesce :public Item_func_numhybrid
   enum Item_result result_type () const { return hybrid_type; }
   const char *func_name() const { return "coalesce"; }
   table_map not_null_tables() const { return 0; }
+  enum_field_types field_type() const { return cached_field_type; }
 };
 
 
 class Item_func_ifnull :public Item_func_coalesce
 {
 protected:
-  enum_field_types cached_field_type;
   bool field_type_defined;
 public:
   Item_func_ifnull(Item *a, Item *b) :Item_func_coalesce(a,b) {}
@@ -677,6 +678,7 @@ class Item_func_ifnull :public Item_func_coalesce
 class Item_func_if :public Item_func
 {
   enum Item_result cached_result_type;
+  enum_field_types cached_field_type;
 public:
   Item_func_if(Item *a,Item *b,Item *c)
     :Item_func(a,b,c), cached_result_type(INT_RESULT)
@@ -686,6 +688,7 @@ class Item_func_if :public Item_func
   String *val_str(String *str);
   my_decimal *val_decimal(my_decimal *);
   enum Item_result result_type () const { return cached_result_type; }
+  enum_field_types field_type() const { return cached_field_type; }
   bool fix_fields(THD *, Item **);
   void fix_length_and_dec();
   uint decimal_precision() const;
@@ -722,6 +725,7 @@ class Item_func_case :public Item_func
   uint ncases;
   Item_result cmp_type;
   DTCollation cmp_collation;
+  enum_field_types cached_field_type;
 public:
   Item_func_case(List<Item> &list, Item *first_expr_arg, Item *else_expr_arg)
     :Item_func(), first_expr_num(-1), else_expr_num(-1),
@@ -749,6 +753,7 @@ class Item_func_case :public Item_func
   uint decimal_precision() const;
   table_map not_null_tables() const { return 0; }
   enum Item_result result_type () const { return cached_result_type; }
+  enum_field_types field_type() const { return cached_field_type; }
   const char *func_name() const { return "case"; }
   void print(String *str);
   Item *find_item(String *str);
@@ -1382,6 +1387,7 @@ class Item_cond :public Item_bool_func
   bool subst_argument_checker(byte **arg) { return TRUE; }
   Item *compile(Item_analyzer analyzer, byte **arg_p,
                 Item_transformer transformer, byte *arg_t);
+  enum_field_types field_type() const { return MYSQL_TYPE_LONGLONG; }
 };
 
 

sql/item_func.cc

@@ -2243,6 +2243,7 @@ void Item_func_min_max::fix_length_and_dec()
   else if ((cmp_type == DECIMAL_RESULT) || (cmp_type == INT_RESULT))
     max_length= my_decimal_precision_to_length(max_int_part+decimals, decimals,
                                             unsigned_flag);
+  cached_field_type= agg_field_type(args, arg_count);
 }
 
 

sql/item_func.h

@@ -692,7 +692,8 @@ class Item_func_min_max :public Item_func
   /* An item used for issuing warnings while string to DATETIME conversion. */
   Item *datetime_item;
   THD *thd;
-
+protected:
+  enum_field_types cached_field_type;
 public:
   Item_func_min_max(List<Item> &list,int cmp_sign_arg) :Item_func(list),
     cmp_type(INT_RESULT), cmp_sign(cmp_sign_arg), compare_as_dates(FALSE),
@@ -705,6 +706,7 @@ class Item_func_min_max :public Item_func
   enum Item_result result_type () const { return cmp_type; }
   bool result_as_longlong() { return compare_as_dates; };
   uint cmp_datetimes(ulonglong *value);
+  enum_field_types field_type() const { return cached_field_type; }
 };
 
 class Item_func_min :public Item_func_min_max

sql/item_timefunc.cc

@@ -3310,7 +3310,7 @@ void Item_func_str_to_date::fix_length_and_dec()
   String format_str(format_buff, sizeof(format_buff), &my_charset_bin), *format;
   maybe_null= 1;
   decimals=0;
-  cached_field_type= MYSQL_TYPE_STRING;
+  cached_field_type= MYSQL_TYPE_DATETIME;
   max_length= MAX_DATETIME_FULL_WIDTH*MY_CHARSET_BIN_MB_MAXLEN;
   cached_timestamp_type= MYSQL_TIMESTAMP_NONE;
   format= args[1]->val_str(&format_str);

sql/mysql_priv.h

@@ -1220,6 +1220,7 @@ my_bool mysql_rm_tmp_tables(void);
 
 /* item_func.cc */
 extern bool check_reserved_words(LEX_STRING *name);
+extern enum_field_types agg_field_type(Item **items, uint nitems);
 
 /* strfunc.cc */
 ulonglong find_set(TYPELIB *lib, const char *x, uint length, CHARSET_INFO *cs,

sql/protocol.cc

@@ -824,6 +824,7 @@ bool Protocol_simple::store(const char *from, uint length,
 	      field_types[field_pos] == MYSQL_TYPE_DECIMAL ||
               field_types[field_pos] == MYSQL_TYPE_BIT ||
               field_types[field_pos] == MYSQL_TYPE_NEWDECIMAL ||
+              field_types[field_pos] == MYSQL_TYPE_NEWDATE ||
 	      (field_types[field_pos] >= MYSQL_TYPE_ENUM &&
 	       field_types[field_pos] <= MYSQL_TYPE_GEOMETRY));
   field_pos++;

sql/sql_insert.cc

@@ -3129,7 +3129,10 @@ static TABLE *create_table_from_items(THD *thd, HA_CREATE_INFO *create_info,
     create_field *cr_field;
     Field *field, *def_field;
     if (item->type() == Item::FUNC_ITEM)
-      field= item->tmp_table_field(&tmp_table);
+      if (item->result_type() != STRING_RESULT)
+        field= item->tmp_table_field(&tmp_table);
+      else
+        field= item->tmp_table_field_from_field_type(&tmp_table);
     else
       field= create_tmp_field(thd, &tmp_table, item, item->type(),
                               (Item ***) 0, &tmp_field, &def_field, 0, 0, 0, 0,