Nested Preload. How to avoid infinite recursion?

Questions & Help Questions
1

Assume 3 schemas: A, B, and C

A has_many B
B has_many C
C preloads a record of B

The scenario above causes an infinite recursion (loop) when preloading recursively under the following condition:
C_record_1 belongs_to B_record_1
C_record_2 belongs_to B_record_2
C_record_1 associates B_record_2
C_record_2 associates B_record_1

How should I efficiently restrict the condition above from happening? Can someone please provide sample code to test the logic above?

2

@ion Preloading does not cause infinite recursion on its own, because when you call preload you do so with a tree, and it only preloads to the depth of that tree. Can you show the code that you have which is recursing infinitely?

3

Per the code you DMed me, the reason it recurses infinitely is that you’re manually introducing infinite recursion.

You should consider doing something more like: A |> preload([b: :c]) |> Repo.all.

Basically the issue is that SQL modeling like you have forms a cyclic graph, and you are looking to return a tree.