[MDEV-28401] incorrect behavior of ALTER ... COLUMN IF [NOT] EXISTS Created: 2022-04-23  Updated: 2023-04-27

Status: Confirmed
Project: MariaDB Server
Component/s: Data Definition - Alter Table
Affects Version/s: 10.2, 10.3, 10.4, 10.5, 10.6, 10.7, 10.8
Fix Version/s: 10.4, 10.5, 10.6

Type: Bug Priority: Major
Reporter: Sergei Golubchik Assignee: Oleksandr Byelkin
Resolution: Unresolved Votes: 0
Labels: None


 Description    

create table t (c date);
 
alter table t change column if exists n c int unique;

this should fail, because the column n does not exist. But it partially succeeds, the result is c date unique.

Another example, for ADD IF NOT EXISTS:

create table t (c date);
 
alter table t add column if not exists c int unique;

Same effect.

 Comments   
Comment by Elena Stepanova [ 2022-04-23 ]

Probably not fail but end with a warning, otherwise what's the point in if exists at all?

What about

create table t (c date);
 
alter table t change column if exists n c int, add unique (c);

will it also stop after unsuccessful first part?

Comment by Sergei Golubchik [ 2022-04-24 ]

Yes, of course. Sorry. By "fail" I meant that no changes should've been done.

If you have two operations in ALTER TABLE, than the second should succeed.

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