How to delete an empty node?

[amaster507 (Anthony Master)]

Here is a reference:

Delete by reverse edge

Hm, there are three problems in this case. The first is that these tasks based on reverse or similar would be very expensive. It would have some impact on performance. The second point is that it is somewhat dangerous to do automated deletions. There are several deletion situations that are out of control. So it is better for the user to decide what to do. The last is that the deletion would have to execute a query internally to collect the reverse UIDs. Technically they are two distinct proc…

@BenW

Am I right in saying that the array of IDs are merely edges to nowhere?

In theory, almost. Every uid list are “merely edges to nowhere” if that is how you want to look at it. A list of uids is a “list of uids” whether those uids have any triples stored in the graph or not.

Yourself coming from the GraphQL API down to the DQL lang itself you are seeing some of the power of the API that you don’t get. You have to now control the deletes of the * * O variety when Dgraph does not allow deletes of this variety.

In the API the schema shows everywhere possible for these uids to exist when being deleted and runs a S P O delete for each possible location where S is each possible pare node P is each edge and O is the node being deleted.

This again shows the need why we need something like the following not only in the GraphQL API, but also in the DQL language itself:

Deleting node with required inverse edges

Best would be to have control over this behaviour by the developer in the schema similar in nature to MySQL use of “ON DELETE” which has options to either set null, restrict, no action, cascade, and set default. That would be interesting to see of that logic could be worked in as a schema directive on an edge. When delete Parent, “set null” is current behaviour on child edge. restrict would block delete if there were any children no action would leave the inverse edge to the uid that is now …