Rails migration to change column type from text to json (Postgresql)
<p>I've been trying unsuccessfully to change a column type in my Postgres database from text to json. Here's what I've tried...</p>

<pre><code>class ChangeNotesTypeInPlaces &lt; ActiveRecord::Migration[5.0]
  def up
    execute 'ALTER TABLE places ALTER COLUMN notes TYPE json USING (notes::json)'
  end

  def down
    execute 'ALTER TABLE places ALTER COLUMN notes TYPE text USING (notes::text)'
  end
end
</code></pre>

<p>Also...</p>

<pre><code>class ChangeNotesTypeInPlaces &lt; ActiveRecord::Migration[5.0]
  def up
    change_column :places, :notes, 'json USING CAST(notes AS json)'
  end

  def down
    change_column :places, :notes, 'text USING CAST(notes AS text)'
  end
end
</code></pre>

<p>Both of these return the same error...</p>

<pre><code>PG::InvalidTextRepresentation: ERROR:  invalid input syntax for type json
</code></pre>