MaridDB 10.3.29 prevents me from deleting a foreign key

All we need is an easy explanation of the problem, so here it is.

This is a minimal example that triggers the error

CREATE TABLE A (
  id bigint NOT NULL AUTO_INCREMENT PRIMARY KEY
);

CREATE TABLE B (
  what tinyint NOT NULL,

  a bigint NOT NULL,

  CONSTRAINT x FOREIGN KEY (a) REFERENCES A(id),
  CONSTRAINT y CHECK (what > 0)
);


SELECT b.a FROM B b;

ALTER TABLE B DROP CONSTRAINT x;

When i run this in a fresh MariaDB instance (docker mariadb:10.3.28) everything works fine.

When MariaDB 10.3.29 was released the query suddenly broke. So, when i run this in a fresh MariaDB instance (docker mariadb:10.3.29) i get the following error message for the last statement:

[42S22][1054] (conn=8) Unknown column '`db`.`b`.`what`' in 'CHECK'

Some weird observations:

  • if i delete the y check and add it after dropping x everything works
  • if i remove the SELECT everything works
  • the b from the error message changes with the table alias from the SELECT statement
  • running the last statement again shows the same error
  • the error message makes no sense at all

So my question: what’s wrong with my SQL?

How to solve :

I know you bored from this bug, So we are here to help you! Take a deep breath and look at the explanation of your problem. We have many solutions to this problem, But we recommend you to use the first method because it is tested & true method that will 100% work for you.

Method 1

This is actually a bug in MariaDB. See the bugtracker.

They recommended to do FLUSH TABLES; before the ALTER statement.

I can confirm that this "hides the bug".

Note: Use and implement method 1 because this method fully tested our system.
Thank you 🙂

All methods was sourced from stackoverflow.com or stackexchange.com, is licensed under cc by-sa 2.5, cc by-sa 3.0 and cc by-sa 4.0

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