Add Add A Generated Column To A PostgreSQL Table as a Rails TIL

rails/add-a-generated-column-to-a-postgresql-table.md

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+# Add A Generated Column To A PostgreSQL Table
+
+As of Rails 7, ActiveRecord supports generated columns for app's backed by a
+PostgreSQL database. This is achieved with a `virtual` column.
+
+```ruby
+class CreateTags < ActiveRecord::Migration[8.0]
+  def change
+    create_table :tags, id: :bigint do |t|
+      t.string :value
+      t.virtual :normalized_value, type: :text, as: "lower(value)", stored: true
+
+      t.timestamps
+    end
+  end
+end
+```
+
+With a table like this, any time we add a record with a `value`, PostgreSQL
+computes and stores the `normalized_value` column based on that.
+
+[source](https://blog.saeloun.com/2022/01/25/rails-7-postgres-support-for-generated-columns/)