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/t/union.test:
  Added test case for bug#12185: Data type aggregation may produce wrong result
  Corrected test case after fix for bug#12185
mysql-test/t/innodb.test:
  Corrected test case after fix for bug#12185
mysql-test/r/union.result:
  Added test case for bug#12185: Data type aggregation may produce wrong result
   Corrected test case after fix for bug#12185
mysql-test/r/innodb.result:
  Corrected test case after fix for bug#12185
mysql-test/r/create.result:
  Corrected the test case after fixing bug#12185
sql/field.h:
  Fixed bug#12185: Data type aggregation may produce wrong result
  Added Field_blob object constructor which sets packlength according to
  max_length argument.
sql/item.cc:
  Fixed bug#12185: Data type aggregation may produce wrong result
  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 creates
  Field_timestamp object for a timestamp field.
  The Item::tmp_table_field_from_field_type() function now uses the Field_blob
  constructor which sets packlength according to max_length.
  The Item_type_holder::display_length() now returns correct NULL length NULL
  length.
sql/field.cc:
  Fixed bug#12185: Data type aggregation may produce wrong result
  Added appropriate Field_timestamp object constructor for using in the 
  Item::tmp_table_field_from_field_type() function.

1 files changed, 23 insertions, 8 deletions

diff --git a/mysql-test/r/union.result b/mysql-test/r/union.result
index eb9e10aa58d..6ef5363d90f 100644
--- a/mysql-test/r/union.result
+++ b/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;