graphql-lightning-talk/README.md

# Extra for experts

Our existing subscription only triggers if someone else uses the `importPerson` mutation to trigger the subscription event - what if we want to let clients know whenever a row is added to our `people` table? Maybe it's added by another service, or something.

In this branch we're using PostgreSQL triggers and stored procedures to send notifications whenever a row is added to the `people` table and we're using `Postgrex.Notifications` to subscribe to them.  A substantial portion of the code for this example comes from [this hacker noon post](https://hackernoon.com/get-notified-of-user-signups-and-plan-changes-automatically-using-postgres-phoenix-pubsub-e67d061b04bc).

Things to look at:

  * `priv/repo/migrations/20180408032823_broadcast_people_table_changes.exs`
  * `lib/faces/gallery/event_listener.ex`

[Demo](http://localhost:4000)

Let's try manually inserting a row (via `psql faces_dev`):
```sql
INSERT INTO "people" ("username", "name", "location", "avatar_url", "inserted_at", "updated_at") VALUES ('pupper', 'pupper', 'the bath', 'https://media.giphy.com/media/3o6Zt9ved5rCuidNlK/giphy.gif', NOW(), NOW());
```

I want to point out that this is a really bad idea, mostly for the same reasons that [Rails ActiveRecord callbacks are a bad idea](http://samuelmullen.com/2013/05/the-problem-with-rails-callbacks/).

Next, move on to `step-7`.