From: Steve Hay
Date: February 26 2004 2:58pm
Subject: Re: Bug in new FOREIGN KEY checks in MySQLInnoDB/4.0.18
List-Archive: http://lists.mysql.com/bugs/15258
Message-Id: <403E0991.10209@uk.radan.com>
MIME-Version: 1.0
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Sinisa Milivojevic wrote:

>Steve Hay writes:
>  
>
>>Hi,
>>
>>I've just upgraded from MySQL 4.0.16 to 4.0.18 and now find that some 
>>commands that used to work without error (dropping and re-creating a 
>>database) no longer work.
>>
>>The error is:
>>
>>    error: 'Cannot delete or update a parent row: a foreign key 
>>constraint fails'
>>
>>which presumably relates to the first item in the InnoDB version history 
>>(http://www.innodb.com/ibman.php#InnoDB.history).  (All the tables in 
>>the database concerned are InnoDB tables.)
>>
>>It appears that the foreign key constraint is being checked even when 
>>dropping the database, which I assume is not intended.
>>
>>I tried a simple case of one table X referencing another table Y, and 
>>"DROP DATABASE" works fine (even with data in it, so foreign key 
>>constraints are not being checked here, which is as I would expect).  I 
>>tried another case with two tables X and Y referencing one table Z, but 
>>still no error.  Finally, I reproduced my problem by having table X 
>>referencing table Y and table Y referencing table Z.
>>
>>The following DOS command-lines result in the error above:
>>
>>I'm running Windows XP SP1.
>>
>>Regards,
>>- Steve
>>
>>    
>>
>
>Hi!
>
>Yes, the above is now the expected behaviour and it is documented in
>our Changelog.
>
>All you have to do is drop tables in the right order.
>  
>
I understand that if I was issuing DROP TABLE statements then I would 
need to put them in the right order, but I'm doing a DROP DATABASE.

Surely foreign key constraints should not be checked when the entire 
database is being dropped.

If they /are/ supposed to be checked then the other cases that I 
mentioned above (where DROP DATABASE worked fine) are not working properly!

- Steve



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