SchemaExporter cascade references

jpgr · **Joined:** Wed Sep 10, 2003 7:09 am **Posts:** 63

Hi,

I'm using SchemaExporter to create a DDL for a mySQL database with InnoDB databases.

In the maping files I have mapped an array with cascade="all" atributte, but there is no reference in the DDL SQL script.

<class name="DocsFolder" ...

<array name="folder" table="Array_DocsFolder" cascade="delete">
<key column="chve1"/>
<index column="i"/>
<many-to-many column="chve2" class="DocsFolder"/>
</array>

<class>

alter table DocsFolder add index (subChvp), add constraint FKFDBC8D769098A83F foreign key (subChvp) references DocsElement (chvp)

alter table Array_XeDocsFolder add index (chve2), add constraint FK95F799BC5A424DE foreign key (chve2) references DocsFolder (subChvp)

alter table Array_XeDocsFolder add index (chve1), add constraint FK95F799BC5A424DD foreign key (chve1) references DocsFolder (subChvp)

What am i doing wrong?

Thanks again,
Joao Rangel

hseta · **Joined:** Thu Oct 30, 2003 6:31 am **Posts:** 8

Hi...

I'm new wih the hibernate and I have the same problem.

If someone can help thanks.

HS

christian · **Posted:** Thu Oct 30, 2003 6:38 am

The "cascade" is an attribute used by Hibernate at runtime for association management, it is not used to generate foreign key constraint options.

hseta · **Joined:** Thu Oct 30, 2003 6:31 am **Posts:** 8

Ok,

but when I try to delete a row from a table, I get this problem....

General error, message from server: "Cannot delete or update a parent row: a foreign key constraint fails"

It's a objec (table) that contains an array whith object's from the same type,

Thanks

hseta · **Joined:** Thu Oct 30, 2003 6:31 am **Posts:** 8

There is any way to skirt this "problem" ??

christian · **Posted:** Thu Oct 30, 2003 7:08 am

I don't understand what you are talking about. How is this problem Hibernate related? You can't delete rows in a table if theres a foreign key constraint on that row.

hseta · **Joined:** Thu Oct 30, 2003 6:31 am **Posts:** 8

But if the foreign keys have the :
references (field) + ON DELETE CASCADE

that shuld be possible rigth?

Is that i want.
There is any way to do that?

Thans
HS

christian · **Posted:** Thu Oct 30, 2003 7:20 am

AFAIK, Hibernate can't generate these FK constraint options, so you have to alter the constraint manually after DDL creation.

hseta · **Joined:** Thu Oct 30, 2003 6:31 am **Posts:** 8

Ok...
Thanks.

I will try.

HS

jpgr · **Joined:** Wed Sep 10, 2003 7:09 am **Posts:** 63

Hi,

I have a problem with object references that i would like to ask:

Imagine that I have class A and B, and A has a reference to B.
If i delete object A with cascade=all option, object B is deleted too.
But if i delete object B, in the same conditions, Objet A is not deleted and i get an exception:

java.sql.BatchUpdateException: General error, message from server: "Cannot delete or update a parent row: a foreign key constraint fails"

How can i solve this problem?

Thanks,
Joao Rangel

emmanuel · **Posted:** Fri Oct 31, 2003 11:08 am

This means B has a reference to A (or to an other object) and need to be set to cascade="all" too

jpgr · **Joined:** Wed Sep 10, 2003 7:09 am **Posts:** 63

If i do that, when i'll try to delete B, he will try to delete A, which refers B. That will cause a loop. Right?

hseta · **Joined:** Thu Oct 30, 2003 6:31 am **Posts:** 8

I have a "bad" but soluction for that.

I have re-generate all references build from hibernate and I put there "ON DELETE CASCADE", "ON DELETE SET NULL"...

I haven't find in hibernate way to do that.

I hope thats help

emmanuel · **Posted:** Fri Oct 31, 2003 12:12 pm

jpgr wrote:

If i do that, when i'll try to delete B, he will try to delete A, which refers B. That will cause a loop. Right?

Do you mean an infinite loop ? No. Hibernate isn't that stupid.

jpgr · **Joined:** Wed Sep 10, 2003 7:09 am **Posts:** 63

ok, you are teelling me that hibernate detects loops... But since i have a uni directional relantion, it doesn't make sense to have a bidirectional mapping.