Subscribe to events emitted by EctoWatch, and cache the changed row. Use the sync/3 function to update an in-memory row or list of rows using the cached version of the changed row.

This library aims to solve the problem of tracking changes of database rows across processes without causing database stampedes. All possible update paths for each pair of schemas that are connected is determined to avoid brute-forcing through all preloaded associations.

Say you have a Post schema that has many Tags associated through a PostsTags schema and you want to automatically update the Tags for the loaded Posts in a LiveView:

appplication.ex

children: [...,
  {EctoSync, repo: TestRepo, watchers: EctoSync.watchers(Post, assocs: [:tags])},
  ...
  ]

PostLive.ex

alias MyApp.Posts.{Post, PostsTags}

def mount(params, session, socket) do
  posts = list_posts(preload: [:tags])
  if connected?(socket) do
    EctoSync.subscribe(Post, assocs: [:tags])
  end

  {:ok, assign(socket, posts: posts)}
end

def handle_info({{PostsTags, _event}, _} = sync_args, socket) do
  {:noreply, update(socket, :posts, &EctoSync.sync(&1, sync_args))}
end

If you want to add preloads to the changed row, this is possible by adding a Map like this:

EctoSync.sync(post, sync_args, preloads: %{Tag => [:posts]})

It is still in an early stage of development and has not been tested in production. I would love to get feedback on this package.

Package on hex.pm here:

Documentation:

Repo: