[MDEV-13240] Wrong warning with MAX(datetime_field) OVER (...) Created: 2017-07-04  Updated: 2017-09-19  Resolved: 2017-07-04

Status: Closed
Project: MariaDB Server
Component/s: Optimizer - Window functions
Affects Version/s: 10.3
Fix Version/s: 10.3.1

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


 Description   

This script:

create or replace table t1(dt datetime);
 
insert into t1 values ('2017-05-17');
 
select max(dt)  over (order by dt rows between 1 following and 1 following)  from t1;
 
show warnings;

returns a correct result:

+----------------------------------------------------------------------+
 
| max(dt)  over (order by dt rows between 1 following and 1 following) |
 
+----------------------------------------------------------------------+
 
| NULL                                                                 |
 
+----------------------------------------------------------------------+

but causes a redundant warning in bb-10.2-ext and 10.3:

+---------+------+------------------------------+
 
| Level   | Code | Message                      |
 
+---------+------+------------------------------+
 
| Warning | 1292 | Incorrect datetime value: '' |
 
+---------+------+------------------------------+

The warning looks wrong. There should not be any warnings.

The problem is not repeatable in 10.2.

The problem happens because Item_window_func::save_in_field() works differently in bb-10.2-ext comparing to 10.2:

  • 10.2 goes through val_str()
  • bb-10.2-ext goes through get_date(), due to Type_handler related changes

After a discussion with Vicentiu, it was decided to fix Item_window_func::val_xxx() to return NULL (instead of an "empty" value, such as 0 for numbers and '' for strings) when force_return_blank is set.

 Comments   
Comment by Vicențiu Ciorbaru [ 2017-07-04 ]

Ok to push

Comment by Alexander Barkov [ 2017-07-04 ]

Pushed to bb-10.2-ext.

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