Add Add A Reference Column With An Index as a rails til

Author: jbranchaud

README.md

@@ -9,7 +9,7 @@ and pairing with smart people at Hashrocket.
 
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@@ -515,6 +515,7 @@ _901 TILs and counting..._
 
 - [Add A Check Constraint To A Table](rails/add-a-check-constraint-to-a-table.md)
 - [Add A Foreign Key Reference To A Table](rails/add-a-foreign-key-reference-to-a-table.md)
+- [Add A Reference Column With An Index](rails/add-a-reference-column-with-an-index.md)
 - [Add React With Webpacker To A New Rails App](rails/add-react-with-webpacker-to-a-new-rails-app.md)
 - [Access Secrets In A Rails 5.2 App](rails/access-secrets-in-a-rails-5-2-app.md)
 - [ActiveRecord Query For This Or That](rails/active-record-query-for-this-or-that.md)

rails/add-a-reference-column-with-an-index.md

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+# Add A Reference Column With An Index
+
+Though I prefer to always back my reference columns with a [foreign
+key](add-a-foreign-key-reference-to-a-table.md), sometimes you may just want to
+add the reference column on its own. Though this could be done manually with
+the `add_column` directive, you can be more explicit with `add_reference` --
+which allows you to specify whether or not an index is to be added.
+
+```ruby
+def up
+  add_reference :books, :authors, index: true
+end
+```
+
+This will add `authors_id` and an index to the `books` table.
+
+You can additionally specify the type of the column. This is handy if you are
+using `uuid`s for all your primary keys.
+
+```ruby
+def up
+  add_reference :books, :authors, type: :uuid, index: true
+end
+```
+
+[source](https://nandovieira.com/using-uuid-with-postgresql-and-activerecord)