[MDEV-9334] ALTER from DECIMAL to BIGINT UNSIGNED returns a wrong result Created: 2015-12-28  Updated: 2018-06-15  Resolved: 2018-06-15

Status: Closed
Project: MariaDB Server
Component/s: OTHER
Affects Version/s: 5.5, 10.0, 10.1, 10.2
Fix Version/s: 10.2.16, 10.3.8, 10.4.0

Type: Bug Priority: Major
Reporter: Alexander Barkov Assignee: Alexander Barkov
Resolution: Fixed Votes: 1
Labels: None

Issue Links:
Blocks
blocks MDEV-4912 Data type plugin API version 1 Closed

 Description    

DROP TABLE IF EXISTS t1;
 
CREATE TABLE t1 (a DECIMAL(30,0));
 
INSERT INTO t1 VALUES (CAST(0xFFFFFFFFFFFFFFFF AS UNSIGNED));
 
SELECT * FROM t1;

returns

+----------------------+
 
| a                    |
 
+----------------------+
 
| 18446744073709551615 |
 
+----------------------+

So far so good.

Now if I do:

ALTER TABLE t1 MODIFY a BIGINT UNSIGNED;
 
SELECT * FROM t1;

it erroneously returns:

+---------------------+
 
| a                   |
 
+---------------------+
 
| 9223372036854775807 |
 
+---------------------+

The expected result is 18446744073709551615.

 Comments   
Comment by Alexander Barkov [ 2018-06-15 ]

The same problem is repeatable with BIT(64)

SET sql_mode='';
 
DROP TABLE IF EXISTS t1;
 
CREATE TABLE t1 (a DECIMAL(30,0));
 
INSERT INTO t1 VALUES (CAST(0xFFFFFFFFFFFFFFFF AS UNSIGNED));
 
ALTER TABLE t1 MODIFY a BIT(64);
 
SHOW WARNINGS;
 
SELECT a+0 FROM t1;


+---------+------+-----------------------------------------------------------------------------+
 
| Level   | Code | Message                                                                     |
 
+---------+------+-----------------------------------------------------------------------------+
 
| Warning | 1916 | Got overflow when converting '18446744073709551615' to INT. Value truncated |
 
+---------+------+-----------------------------------------------------------------------------+


+---------------------+
 
| a+0                 |
 
+---------------------+
 
| 9223372036854775807 |
 
+---------------------+

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