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, 10 insertions, 2 deletions

diff --git a/mysql-test/t/union.test b/mysql-test/t/union.test
index 692f1f509fa..516bc6d4818 100644
--- a/mysql-test/t/union.test
+++ b/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;