Add Connect To A Database By Color as a Heroku TIL

heroku/connect-to-a-database-by-color.md

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+# Connect To A Database By Color
+
+All of your PostgreSQL databases in Heroku are given attachment names that use
+a random color. This might be _pink_, _brown_, _cobalt_, etc. And the
+attachment names then look like `HEROKU_POSTGRESQL_PINK`,
+`HEROKU_POSTGRESQL_BROWN`, `HEROKU_POSTGRESQL_COBALT`, etc.
+
+We can connect to a Heroku-managed PostgreSQL instance from the command-line
+like so:
+
+```bash
+$ heroku pg:psql --app my-app
+```
+
+This is going to connect to the _default_ database which is the one with the
+`DATABASE_URL` attachment.
+
+There are lots of instances where we may have other databases besides the
+primary (e.g. let's say we have a read replica follower). If we want to connect
+to that one, we can do so by _color_.
+
+If that database's attachment is `HEROKU_POSTGRESQL_IVORY`, then we'd connect
+to it like so:
+
+```bash
+$ heroku pg:psql ivory --app my-app
+```
+
+[source](https://devcenter.heroku.com/articles/managing-heroku-postgres-using-cli#pg-psql)