Bug#32848: Data type conversion bug in union subselects in MySQL 5.0.38

There were two problems when inferring the correct field types resulting from
UNION queries.
- If the type is NULL for all corresponding fields in the UNION, the resulting 
  type would be NULL, while the type is BINARY(0) if there is just a single 
  SELECT NULL.
- If one SELECT in the UNION uses a subselect, a temporary table is created
  to represent the subselect, and the result type defaults to a STRING type,
  hiding the fact that the type was unknown(just a NULL value).
Fixed by remembering whenever a field was created from a NULL value and pass
type NULL to the type coercion if that is the case, and creating a string field
as result of UNION only if the type would otherwise be NULL.
parent 7f67efcc
...@@ -1389,4 +1389,28 @@ select @var; ...@@ -1389,4 +1389,28 @@ select @var;
1 1
(select 2) union (select 1 into @var); (select 2) union (select 1 into @var);
ERROR 42000: Result consisted of more than one row ERROR 42000: Result consisted of more than one row
CREATE TABLE t1 (a INT);
INSERT INTO t1 VALUES (1), (2), (3);
CREATE TABLE t2 SELECT * FROM (SELECT NULL) a UNION SELECT a FROM t1;
DESC t2;
Field Type Null Key Default Extra
NULL int(11) YES NULL
CREATE TABLE t3 SELECT a FROM t1 UNION SELECT * FROM (SELECT NULL) a;
DESC t3;
Field Type Null Key Default Extra
a int(11) YES NULL
CREATE TABLE t4 SELECT NULL;
DESC t4;
Field Type Null Key Default Extra
NULL binary(0) YES NULL
CREATE TABLE t5 SELECT NULL UNION SELECT NULL;
DESC t5;
Field Type Null Key Default Extra
NULL binary(0) YES NULL
CREATE TABLE t6
SELECT * FROM (SELECT * FROM (SELECT NULL)a) b UNION SELECT a FROM t1;
DESC t6;
Field Type Null Key Default Extra
NULL int(11) YES NULL
DROP TABLE t1, t2, t3, t4, t5, t6;
End of 5.0 tests End of 5.0 tests
...@@ -877,4 +877,28 @@ DROP TABLE t1; ...@@ -877,4 +877,28 @@ DROP TABLE t1;
select @var; select @var;
--error 1172 --error 1172
(select 2) union (select 1 into @var); (select 2) union (select 1 into @var);
#
# Bug#32848: Data type conversion bug in union subselects in MySQL 5.0.38
#
CREATE TABLE t1 (a INT);
INSERT INTO t1 VALUES (1), (2), (3);
CREATE TABLE t2 SELECT * FROM (SELECT NULL) a UNION SELECT a FROM t1;
DESC t2;
CREATE TABLE t3 SELECT a FROM t1 UNION SELECT * FROM (SELECT NULL) a;
DESC t3;
CREATE TABLE t4 SELECT NULL;
DESC t4;
CREATE TABLE t5 SELECT NULL UNION SELECT NULL;
DESC t5;
CREATE TABLE t6
SELECT * FROM (SELECT * FROM (SELECT NULL)a) b UNION SELECT a FROM t1;
DESC t6;
DROP TABLE t1, t2, t3, t4, t5, t6;
--echo End of 5.0 tests --echo End of 5.0 tests
...@@ -1304,7 +1304,8 @@ Field::Field(char *ptr_arg,uint32 length_arg,uchar *null_ptr_arg, ...@@ -1304,7 +1304,8 @@ Field::Field(char *ptr_arg,uint32 length_arg,uchar *null_ptr_arg,
field_name(field_name_arg), field_name(field_name_arg),
query_id(0), key_start(0), part_of_key(0), part_of_sortkey(0), query_id(0), key_start(0), part_of_key(0), part_of_sortkey(0),
unireg_check(unireg_check_arg), unireg_check(unireg_check_arg),
field_length(length_arg), null_bit(null_bit_arg) field_length(length_arg), null_bit(null_bit_arg),
is_created_from_null_item(FALSE)
{ {
flags=null_ptr ? 0: NOT_NULL_FLAG; flags=null_ptr ? 0: NOT_NULL_FLAG;
comment.str= (char*) ""; comment.str= (char*) "";
......
...@@ -88,6 +88,16 @@ public: ...@@ -88,6 +88,16 @@ public:
uint field_index; // field number in fields array uint field_index; // field number in fields array
uint16 flags; uint16 flags;
uchar null_bit; // Bit used to test null bit uchar null_bit; // Bit used to test null bit
/**
If true, this field was created in create_tmp_field_from_item from a NULL
value. This means that the type of the field is just a guess, and the type
may be freely coerced to another type.
@see create_tmp_field_from_item
@see Item_type_holder::get_real_type
*/
bool is_created_from_null_item;
Field(char *ptr_arg,uint32 length_arg,uchar *null_ptr_arg,uchar null_bit_arg, Field(char *ptr_arg,uint32 length_arg,uchar *null_ptr_arg,uchar null_bit_arg,
utype unireg_check_arg, const char *field_name_arg, utype unireg_check_arg, const char *field_name_arg,
......
...@@ -6569,6 +6569,8 @@ enum_field_types Item_type_holder::get_real_type(Item *item) ...@@ -6569,6 +6569,8 @@ enum_field_types Item_type_holder::get_real_type(Item *item)
*/ */
Field *field= ((Item_field *) item)->field; Field *field= ((Item_field *) item)->field;
enum_field_types type= field->real_type(); enum_field_types type= field->real_type();
if (field->is_created_from_null_item)
return MYSQL_TYPE_NULL;
/* work around about varchar type field detection */ /* work around about varchar type field detection */
if (type == MYSQL_TYPE_STRING && field->type() == MYSQL_TYPE_VAR_STRING) if (type == MYSQL_TYPE_STRING && field->type() == MYSQL_TYPE_VAR_STRING)
return MYSQL_TYPE_VAR_STRING; return MYSQL_TYPE_VAR_STRING;
...@@ -6820,6 +6822,8 @@ Field *Item_type_holder::make_field_by_type(TABLE *table) ...@@ -6820,6 +6822,8 @@ Field *Item_type_holder::make_field_by_type(TABLE *table)
Field::NONE, name, Field::NONE, name,
table, get_set_pack_length(enum_set_typelib->count), table, get_set_pack_length(enum_set_typelib->count),
enum_set_typelib, collation.collation); enum_set_typelib, collation.collation);
case MYSQL_TYPE_NULL:
return make_string_field(table);
default: default:
break; break;
} }
......
...@@ -8974,6 +8974,8 @@ static Field *create_tmp_field_from_item(THD *thd, Item *item, TABLE *table, ...@@ -8974,6 +8974,8 @@ static Field *create_tmp_field_from_item(THD *thd, Item *item, TABLE *table,
*((*copy_func)++) = item; // Save for copy_funcs *((*copy_func)++) = item; // Save for copy_funcs
if (modify_item) if (modify_item)
item->set_result_field(new_field); item->set_result_field(new_field);
if (item->type() == MYSQL_TYPE_NULL)
new_field->is_created_from_null_item= TRUE;
return new_field; return new_field;
} }
......
Markdown is supported
0%
or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment