[MDEV-8489] Multi-UPDATE does not report truncated fields correctly Created: 2015-07-17  Updated: 2023-11-28

Status: Open
Project: MariaDB Server
Component/s: Data Manipulation - Update
Affects Version/s: 5.5, 10.0, 10.1, 10.2, 10.3, 10.4, 10.5, 10.6, 10.7, 10.8, 10.9, 10.10, 10.11
Fix Version/s: 10.4, 10.5, 10.6, 10.11

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


 Description   

This script:

DROP TABLE IF EXISTS t1;
 
CREATE TABLE t1 (a INT);
 
INSERT INTO t1 VALUES (1);
 
UPDATE t1 SET t1.a='';

correctly reports 1 warning:

Rows matched: 1  Changed: 1  Warnings: 1

Looks correct so far.

Now I change the script slightly, to use a multi-UPDATE statement:

DROP TABLE IF EXISTS t1,t2;
 
CREATE TABLE t1 (a INT);
 
CREATE TABLE t2(a INT);
 
INSERT INTO t1 VALUES (1);
 
INSERT INTO t2 VALUES (1);
 
UPDATE t1,t2 SET t1.a='';

it reports no warnings:

Rows matched: 1  Changed: 1  Warnings: 0

A related problem:

DROP FUNCTION IF EXISTS f1;
 
DELIMITER //
 
CREATE FUNCTION f1 (a VARCHAR(20)) RETURNS INT
 
BEGIN
 
  DECLARE d INT;
 
  SET d= a;
 
  SET d= a;
 
  SET d= a; // Assign 3 times, to have multiple truncations on a bad string argument
 
  RETURN d;
 
END;
 
//
 
DELIMITER ;
 
SELECT f1('123x');
 
 
 
DROP TABLE IF EXISTS t1;
 
CREATE TABLE t1 (a INT);
 
INSERT INTO t1 VALUES (0);
 
UPDATE t1 SET a=f1('123x');
 
UPDATE t1, t1 t2 SET t1.a=f1('123x');

The above script returns:

MariaDB [test]> UPDATE t1 SET a=f1('123x');
 
Query OK, 1 row affected (0.03 sec)
 
Rows matched: 1  Changed: 1  Warnings: 0
 
 
 
MariaDB [test]> UPDATE t1, t1 t2 SET t1.a=f1('123x');
 
Query OK, 0 rows affected (0.04 sec)
 
Rows matched: 1  Changed: 0  Warnings: 3

The multi-table UPDATE incorrectly says "Warnings: 3" , that is it counted the truncations that happened inside SP. It should only count the number of truncations that happened in fields, which is 0.

 Comments   
Comment by Alexander Barkov [ 2015-07-17 ]

The proposed plan is:

  • Make sure the code does not to increment thd->cuted_fields if thd->count_cuted_fields is false in all cases, for all data types
  • Change this code in mysql_update():

        my_snprintf(buff, sizeof(buff), ER(ER_UPDATE_INFO), (ulong) found,
    		 
                    (ulong) updated,
    		 
                    (ulong) thd->get_stmt_da()->current_statement_warn_count());

    regular UPDATE to use thd->cuted_fields instead of current_statement_warn_count()(
    to use thd->cuted_fields instead of current_statement_warn_count().

  • Change all Field_xxx::store() to make sure to update thd->cuted_fields properly for all kinds of truncation, e.g. stroring an empty string to a number, storing '1x' to a number, storing 'x' to a number.
Generated at Thu Feb 08 07:27:32 UTC 2024 using Jira 8.20.16#820016-sha1:9d11dbea5f4be3d4cc21f03a88dd11d8c8687422.