Data model advice asked for

[clsturgeon]

@Scott_Sauyet

That’s not just a start. That’s a fantastic start!

Thanks. Let’s move this discussion to a new thread at:

Cascade delete, is this supported with a hook on th-deleting-tiddler?

On a couple of threads I have discussed creating a JavaScript method to detect the deletion of a tiddler, upon which the JavaScript invokes actions to update all title and list fields this newly deleted tiddler is referencing. This works well. Thanks to @saqimtiaz However, what if the next step in the hook logic was to delete this tiddler being referenced? As an experiment, I invoked a delete action request–which also worked. What did not work is that this request to delete another tiddler did…

I suspect we are highjacking this one.

I have a working piece of code, that updates Title and List values and then decides if the tiddler being updated should also be removed. This logic is generic. In relational database models, we configure cascade deletes in the database foreign keys. With that in mind, I thought then each entity must be configured to support a cascade delete. In my example I previously provided, I think if any list field in an event-role was empty (after an update) it would mean the tiddler should be removed. A role-event tiddler is not valid if the people list field is empty, or if the role list field is empty or the event list field is empty. Therefore, TW filters can be used to determine if a tiddler should be removed. E.g.

[tag[event-role]!has[people]]
[tag[event-role]!has[role]]
[tag[event-role]!has[event]]

The user creates one filter for each rule. So, I can create one or more rules for any given entity. I could do anothers for role, people and events. All the rules get executed, and if any 1 of them becomes true, the tiddler is deleted.

In my app there will be entities like event-role that can be cascade deleted, and others that cannot be by definition.