Question

I have an embedded (updatable) tree structure in an array – considering the upcoming $slice abilities to select only parts of an array, I’m thinking of implementing a way to display only one (sub-)branch of the tree.

If I understand correctly, to do this efficiently, I’d have to save the path (grandparent.parent.child) in each item in the tree.

However, I can’t see a nice way of managing these paths (when updating), looks like these are my options:

1. trusting client-side parameters blindly and just inserting to the array without verification of the path.
2. fetching the entire document, compute the path and only then store the new item

What do you think? Branches cannot move around in the tree, they are only inserted/updated.

Answer 1

I just didn’t think about deep enough. At the time of insertion I currently have only a parent-id, but when I start having paths – I can use them to find the parent, then I can verify that the parent exist exactly in the same way as I’m currently doing it with parent-id.

The only problem with this approach is that I’d need to save the path even for branches that don’t have a parent (children of root).

Then, I can just search for them in the array with the mongo query and if they don’t exist the path is bogus and I stop the update.