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From Martin Dirichs <nab...@dirichs.fastmail.fm>
Subject Re: Composite foreign keys with MySQL
Date Sun, 03 May 2009 11:59:54 GMT

Yes, and there is no mention of this particular issue.

  -Martin.


Rick Curtis wrote:
> 
> Here are the known MySQL issues --
> http://openjpa.apache.org/builds/latest/docs/manual/manual.html#dbsupport_mysql_issues.
> 
> -Rick
> 
> 
> Martin Dirichs wrote:
>> 
>> Hi,
>> 
>> wondering why OpenJPA's MappingTool refused to add a foreign key
>> constraint to the database (error message: openjpa.jdbc.Schema - The
>> foreign key "<foreignkey>" was not added to table "[...]"), I discovered
>> that composite foreign key support is explicitly disabled for MySQL.
>> These are the relevant code lines in
>> org.apache.openjpa.jdbc.sql.MySQLDictionary:
>> 
>>     protected String getForeignKeyConstraintSQL(ForeignKey fk) {
>>         // mysql does not support composite foreign keys
>>         if (fk.getColumns().length > 1)
>>             return null;
>>         return super.getForeignKeyConstraintSQL(fk);
>>     }
>> 
>> For all I know, composite foreign keys are possible with MySQL. At least,
>> a statement like
>> 
>> ALTER TABLE detail ADD CONSTRAINT constraint_x FOREIGN KEY (masterId1,
>> masterId2) REFERENCES master (masterId1, masterId2);
>> 
>> works perfectly well. Are there other deficits with MySQL foreign key
>> handling I am not aware of or are the above lines in MySQLDictionary.java
>> outdated / wrong?
>> 
>>   Regards,
>>     Martin.
>> 
>> 
> 
> 

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