[MDEV-10305] CAST(string_expr AS SIGNED) does not truncate huge numbers well Created: 2016-06-29  Updated: 2016-06-29

Status: Open
Project: MariaDB Server
Component/s: OTHER
Affects Version/s: 10.0, 10.1, 10.2
Fix Version/s: 10.2

Type: Bug Priority: Minor
Reporter: Alexander Barkov Assignee: Alexander Barkov
Resolution: Unresolved Votes: 0
Labels: None


 Description   

Implicit CAST from string to signed bigint truncates the number the to maximum possible 64-bit signed value:

DROP TABLE IF EXISTS t1;
 
CREATE TABLE t1 (a BIGINT);
 
INSERT INTO t1 VALUES ('99999999999999999999');
 
SELECT * FROM t1;


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

So does explicit CAST from DECIMAL to SIGNED:

SELECT CAST(99999999999999999999 AS SIGNED);


+--------------------------------------+
 
| CAST(99999999999999999999 AS SIGNED) |
 
+--------------------------------------+
 
|                  9223372036854775807 |
 
+--------------------------------------+

So does explicit CAST from DOUBLE to SIGNED:

SELECT CAST(99999999999999999999e0 AS SIGNED);


+----------------------------------------+
 
| CAST(99999999999999999999e0 AS SIGNED) |
 
+----------------------------------------+
 
|                    9223372036854775807 |
 
+----------------------------------------+

Explicit CAST from string to SIGNED works differently:

SELECT CAST('99999999999999999999' AS SIGNED);


+----------------------------------------+
 
| CAST('99999999999999999999' AS SIGNED) |
 
+----------------------------------------+
 
|                                     -1 |
 
+----------------------------------------+

This looks wrong. Explicit CAST from string to SIGNED should also return 9223372036854775807.

 Comments   
Comment by Alexander Barkov [ 2016-06-29 ]

Dynamic columns also do not work well:

SELECT COLUMN_GET(COLUMN_CREATE(0,'99999999999999999999'), 0 AS SIGNED);


+------------------------------------------------------------------+
 
| COLUMN_GET(COLUMN_CREATE(0,'99999999999999999999'), 0 AS SIGNED) |
 
+------------------------------------------------------------------+
 
|                                                               -1 |
 
+------------------------------------------------------------------+

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