WalEx - Listen to Postgres change events and do stuff with the data directly in Elixir

Just added some DSL magic to WalEx. WalEx allows you to listen to change events on your Postgres tables then perform callback-like actions with the data. It includes a diff of the data as well so that you can match on specific changes.

The codebase was originally based off of Supabase’s excellent realtime library which I then later refactored to use Postgrex’s new Replication capabilities. The reason I pulled it out into it’s own library is I wanted to work with the data directly in Elixir as well as track diffs.

So now you can set up an event listener like this:

defmodule MyApp.UserEvent do
  use WalEx.Event, name: MyApp

  # any event
  on_event(:user, fn {:ok, user} ->
    IO.inspect(on_event: user)
    # do something with user data (Event Struct)
  end)

  on_insert(:user, fn {:ok, user} ->
    IO.inspect(on_insert: user)
  end)

  on_update(:user, fn {:ok, user} ->
    IO.inspect(on_update: user)
  end)

  on_delete(:user, fn {:ok, user} ->
    IO.inspect(on_delete: user)
  end)

I’m also considering adding a configuration-only option so that non-Elixir folks can use the library to listen to Postgres changes and send them wherever they need. Feedback and ideas on how I can improve WalEx is much appreciated!