Fixed bug#12185: Data type aggregation may produce wrong result

The Item::tmp_table_field_from_field_type() function creates Field_datetime
object instead of Field_timestamp object for timestamp field thus always
changing data type is a tmp table is used.

The Field_blob object constructor which is used in the 
Item::tmp_table_field_from_field_type() is always setting packlength field of
newly created blob to 4. This leads to changing fields data type for example
from the blob to the longblob if a temporary table is used.

The Item::make_string_field() function always converts Field_string objects 
to Field_varstring objects. This leads to changing data type from the 
char/binary to varchar/varbinary.

Added appropriate Field_timestamp object constructor for using in the 
Item::tmp_table_field_from_field_type() function.

Added Field_blob object constructor which sets pack length according to
max_length argument.

The Item::tmp_table_field_from_field_type() function now creates
Field_timestamp object for a timestamp field.

The Item_type_holder::display_length() now returns correct NULL length NULL
length. 

The Item::make_string_field() function now doesn't change Field_string to
Field_varstring in the case of Item_type_holder. 

The Item::tmp_table_field_from_field_type() function now uses the Field_blob
constructor which sets packlength according to max_length.

mysql-test/r/create.result

@@ -452,7 +452,7 @@ t2	CREATE TABLE `t2` (
   `ifnull(h,h)` decimal(5,4) default NULL,
   `ifnull(i,i)` year(4) default NULL,
   `ifnull(j,j)` date default NULL,
-  `ifnull(k,k)` datetime NOT NULL default '0000-00-00 00:00:00',
+  `ifnull(k,k)` timestamp NOT NULL default '0000-00-00 00:00:00',
   `ifnull(l,l)` datetime default NULL,
   `ifnull(m,m)` varchar(1) default NULL,
   `ifnull(n,n)` varchar(3) default NULL,

mysql-test/r/innodb.result

@@ -1473,8 +1473,8 @@ Error	1146	Table 'test.t4' doesn't exist
 drop table t1,t2,t3;
 create table t1 (id int,  name char(10) not null,  name2 char(10) not null) engine=innodb;
 insert into t1 values(1,'first','fff'),(2,'second','sss'),(3,'third','ttt');
-select name2 from t1  union all  select name from t1 union all select id from t1;
-name2
+select trim(name2) from t1  union all  select trim(name) from t1 union all select trim(id) from t1;
+trim(name2)
 fff
 sss
 ttt

mysql-test/r/union.result

@@ -691,9 +691,9 @@ t1	CREATE TABLE `t1` (
   `da` datetime default NULL
 ) ENGINE=MyISAM DEFAULT CHARSET=latin1
 drop table t1;
-create table t1 SELECT dt from t2 UNION select sc from t2;
-select * from t1;
-dt
+create table t1 SELECT dt from t2 UNION select trim(sc) from t2;
+select trim(dt) from t1;
+trim(dt)
 1972-10-22 11:50:00
 testc
 show create table t1;
@@ -732,7 +732,7 @@ tetetetetest
 show create table t1;
 Table	Create Table
 t1	CREATE TABLE `t1` (
-  `dt` longblob
+  `dt` blob
 ) ENGINE=MyISAM DEFAULT CHARSET=latin1
 drop table t1;
 create table t1 SELECT sv from t2 UNION select b from t2;
@@ -743,7 +743,7 @@ tetetetetest
 show create table t1;
 Table	Create Table
 t1	CREATE TABLE `t1` (
-  `sv` longblob
+  `sv` blob
 ) ENGINE=MyISAM DEFAULT CHARSET=latin1
 drop table t1;
 create table t1 SELECT i from t2 UNION select d from t2 UNION select b from t2;
@@ -755,7 +755,7 @@ tetetetetest
 show create table t1;
 Table	Create Table
 t1	CREATE TABLE `t1` (
-  `i` longblob
+  `i` blob
 ) ENGINE=MyISAM DEFAULT CHARSET=latin1
 drop table t1;
 create table t1 SELECT sv from t2 UNION select tx from t2;
@@ -766,7 +766,7 @@ teeeeeeeeeeeest
 show create table t1;
 Table	Create Table
 t1	CREATE TABLE `t1` (
-  `sv` longtext
+  `sv` text
 ) ENGINE=MyISAM DEFAULT CHARSET=latin1
 drop table t1;
 create table t1 SELECT b from t2 UNION select tx from t2;
@@ -777,7 +777,7 @@ teeeeeeeeeeeest
 show create table t1;
 Table	Create Table
 t1	CREATE TABLE `t1` (
-  `b` longblob
+  `b` blob
 ) ENGINE=MyISAM DEFAULT CHARSET=latin1
 drop table t1,t2;
 create table t1 select 1 union select -1;
@@ -1306,3 +1306,18 @@ id
 5
 99
 drop table t1;
+create table t1(f1 char(1), f2 char(5), f3 binary(1), f4 binary(5), f5 timestamp, f6 varchar(1) character set utf8 collate utf8_general_ci, f7 text);
+create table t2 as select *, f6 as f8 from t1 union select *, f7 from t1;
+show create table t2;
+Table	Create Table
+t2	CREATE TABLE `t2` (
+  `f1` char(1) default NULL,
+  `f2` char(5) default NULL,
+  `f3` binary(1) default NULL,
+  `f4` binary(5) default NULL,
+  `f5` timestamp NOT NULL default '0000-00-00 00:00:00',
+  `f6` varchar(1) character set utf8 default NULL,
+  `f7` text,
+  `f8` text character set utf8
+) ENGINE=MyISAM DEFAULT CHARSET=latin1
+drop table t1, t2;

mysql-test/t/innodb.test

@@ -1079,7 +1079,7 @@ drop table t1,t2,t3;
 #
 create table t1 (id int,  name char(10) not null,  name2 char(10) not null) engine=innodb;
 insert into t1 values(1,'first','fff'),(2,'second','sss'),(3,'third','ttt');
-select name2 from t1  union all  select name from t1 union all select id from t1;
+select trim(name2) from t1  union all  select trim(name) from t1 union all select trim(id) from t1;
 drop table t1;
 
 #

mysql-test/t/union.test

@@ -390,8 +390,8 @@ create table t1 SELECT da from t2 UNION select dt from t2;
 select * from t1;
 show create table t1;
 drop table t1;
-create table t1 SELECT dt from t2 UNION select sc from t2;
-select * from t1;
+create table t1 SELECT dt from t2 UNION select trim(sc) from t2;
+select trim(dt) from t1;
 show create table t1;
 drop table t1;
 create table t1 SELECT dt from t2 UNION select sv from t2;
@@ -793,3 +793,11 @@ select id from t1 union all select 99 order by 1;
 drop table t1;
 
 # End of 4.1 tests
+
+#
+# Bug#12185: Data type aggregation may produce wrong result
+#
+create table t1(f1 char(1), f2 char(5), f3 binary(1), f4 binary(5), f5 timestamp, f6 varchar(1) character set utf8 collate utf8_general_ci, f7 text);
+create table t2 as select *, f6 as f8 from t1 union select *, f7 from t1;
+show create table t2;
+drop table t1, t2;

sql/field.cc

@@ -4484,6 +4484,24 @@ Field_timestamp::Field_timestamp(char *ptr_arg, uint32 len_arg,
 }
 
 
+Field_timestamp::Field_timestamp(bool maybe_null_arg,
+                                 const char *field_name_arg,
+                                 struct st_table *table_arg, CHARSET_INFO *cs)
+  :Field_str((char*) 0, 19, maybe_null_arg ? (uchar*) "": 0, 0,
+	     NONE, field_name_arg, table_arg, cs)
+{
+  /* For 4.0 MYD and 4.0 InnoDB compatibility */
+  flags|= ZEROFILL_FLAG | UNSIGNED_FLAG;
+  if (table && !table->timestamp_field &&
+      unireg_check != NONE)
+  {
+    /* This timestamp has auto-update */
+    table->timestamp_field= this;
+    flags|=TIMESTAMP_FLAG;
+  }
+}
+
+
 /*
   Get auto-set type for TIMESTAMP field.
 

sql/field.h

@@ -781,6 +781,8 @@ public:
 		  enum utype unireg_check_arg, const char *field_name_arg,
 		  struct st_table *table_arg,
 		  CHARSET_INFO *cs);
+  Field_timestamp(bool maybe_null_arg, const char *field_name_arg,
+		 struct st_table *table_arg, CHARSET_INFO *cs);
   enum_field_types type() const { return FIELD_TYPE_TIMESTAMP;}
   enum ha_base_keytype key_type() const { return HA_KEYTYPE_ULONG_INT; }
   enum Item_result cmp_type () const { return INT_RESULT; }
@@ -1129,6 +1131,21 @@ public:
   {
     flags|= BLOB_FLAG;
   }
+  Field_blob(uint32 len_arg,bool maybe_null_arg, const char *field_name_arg,
+	     struct st_table *table_arg, CHARSET_INFO *cs, bool set_packlength)
+    :Field_longstr((char*) 0,len_arg, maybe_null_arg ? (uchar*) "": 0, 0,
+                   NONE, field_name_arg, table_arg, cs)
+  {
+    flags|= BLOB_FLAG;
+    packlength= 4;
+    if (set_packlength)
+    {
+      uint32 char_lengt= len_arg/cs->mbmaxlen;
+      packlength= char_length <= 255 ? 1 :
+                  char_length <= 65535 ? 2 :
+                  char_length <= 16777215 ? 3 : 4;
+    }
+  }
   enum_field_types type() const { return FIELD_TYPE_BLOB;}
   enum ha_base_keytype key_type() const
     { return binary() ? HA_KEYTYPE_VARBINARY2 : HA_KEYTYPE_VARTEXT2; }

sql/item.cc

@@ -3874,7 +3874,9 @@ Field *Item::make_string_field(TABLE *table)
   if (max_length/collation.collation->mbmaxlen > CONVERT_IF_BIGGER_TO_BLOB)
     return new Field_blob(max_length, maybe_null, name, table,
                           collation.collation);
-  if (max_length > 0)
+  /* Item_type_holder holds the exact type, do not change it */
+  if (max_length > 0 &&
+      (type() != Item::TYPE_HOLDER || field_type() != MYSQL_TYPE_STRING))
     return new Field_varstring(max_length, maybe_null, name, table,
                                collation.collation);
   return new Field_string(max_length, maybe_null, name, table,
@@ -3938,6 +3940,7 @@ Field *Item::tmp_table_field_from_field_type(TABLE *table)
   case MYSQL_TYPE_TIME:
     return new Field_time(maybe_null, name, table, &my_charset_bin);
   case MYSQL_TYPE_TIMESTAMP:
+    return new Field_timestamp(maybe_null, name, table, &my_charset_bin);
   case MYSQL_TYPE_DATETIME:
     return new Field_datetime(maybe_null, name, table, &my_charset_bin);
   case MYSQL_TYPE_YEAR:
@@ -3961,7 +3964,11 @@ Field *Item::tmp_table_field_from_field_type(TABLE *table)
   case MYSQL_TYPE_LONG_BLOB:
   case MYSQL_TYPE_BLOB:
   case MYSQL_TYPE_GEOMETRY:
-    return new Field_blob(max_length, maybe_null, name, table,
+    if (this->type() == Item::TYPE_HOLDER)
+      return new Field_blob(max_length, maybe_null, name, table,
+                          collation.collation, 1);
+    else
+      return new Field_blob(max_length, maybe_null, name, table,
                           collation.collation);
     break;					// Blob handled outside of case
   }
@@ -6117,7 +6124,7 @@ uint32 Item_type_holder::display_length(Item *item)
   case MYSQL_TYPE_DOUBLE:
     return 53;
   case MYSQL_TYPE_NULL:
-    return 4;
+    return 0;
   case MYSQL_TYPE_LONGLONG:
     return 20;
   case MYSQL_TYPE_INT24: