[development] Foreign keys in Drupal 6

[Dries Buytaert]

On 04 Jun 2007, at 05:14, David Strauss wrote:

> Assuming the foreign keys patch to the schema API makes it in,  
> there are
> four ways we can approach foreign keys in Drupal 6.
>
> 1. Don't use them at all. Just provide the schema API for contrib
> modules with higher database requirements than core.
>
> 2. Configure foreign keys as RESTRICT on delete. This will have no
> effect on MyISAM, but it will improve code quality because operations
> creating inconsistency would fail. Such operations would then be
> rewritten to manipulate the database in a consistent way.
>
> 3. Configure foreign keys as CASCADE on delete and have extra PHP run
> whenever a query manipulates a database using MyISAM. Basically,
> whenever a DELETE query gets sent to a MyISAM system, we would convert
> it to a SELECT query to identify the rows that would be deleted. Then,
> we would delete the records attached with foreign keys. Finally, we
> would run the original DELETE query. This would have to be recursive.
>
> 4. Configure foreign keys as CASCADE on delete and have modules
> conditionally run queries in their deletion hooks depending on the
> storage engine. If a module doesn't check the storage engine type, the
> DELETE it runs would simply be redundant.

Personally, I think #2 would be a great first step.  We could then  
consider #3 or #4 for Drupal 7.

--
Dries Buytaert  ::  http://www.buytaert.net/