HasMany relationships load all objects and then count on collection page

[RCulpepp]

• What were you trying to do?
  I was attempting to load an index of resources that had hundreds of thousands of associated resources through a has_many relationship. When querying, it is attempting to load all objects in memory, before counting. Thus slowing down the app (unnecessarily and unexpectedly) since all that displays is a count for those associated objects.

I have something like this:

resource_dashboard.rb

ATTRIBUTE_TYPES = {
  associated_resources: Field::HasMany
}.freeze

COLLECTION_ATTRIBUTES = [
  :associated_resources,
].freeze

• What did you end up with (logs, or, even better, example apps are great!)?
  A very slow response!

I've come up with a solution that'll I'll submit as a PR.

• What versions are you running?
  • Rails 5.0.7.2
  • administrate 0.11.0

[pablobm]

I think this is the same as #1464. I'm closing this one as the other one has more discussion and detail.

[gabriel]

You referenced this issue (#1464), did you mean to point to a different one?

[pablobm]

Ooops. And not the first time I do this either 😓

I'm not sure which issue I meant to link to. It might be #1697, where I offer a potential solution that I'll quote here:

Perhaps this should be solved outside Administrate? I'm thinking of using the counter_cache option to belongs_to, and show this in the index page, instead of the HasMany field. See: https://guides.rubyonrails.org/association_basics.html#options-for-belongs-to-counter-cache