title: Postgres cascade delete doesn't work
body: <p>I have two tables:</p>
  
  <pre><code>CREATE TABLE cars(
      id SERIAL PRIMARY KEY,
      brand VARCHAR(100),
      model VARCHAR(100),
      transmission VARCHAR(50),
      engine REAL,
      year INTEGER
  );
  </code></pre>
  
  <p>and</p>
  
  <pre><code>CREATE TABLE ads(
  id SERIAL PRIMARY KEY,
  description VARCHAR(500),
  price INTEGER,
  sold BOOLEAN,
  create_date TIMESTAMP,
  car_id INTEGER REFERENCES cars(id) ON DELETE CASCADE
  );
  </code></pre>
  
  <p>When I delete some ad like</p>
  
  <pre><code>delete from ads where id=1;
  </code></pre>
  
  <p>it works fine - and deletes, but the appropriate car doesn't delete. Why? 
  I didn't find proper answer in the web. Thanks for expected help.</p>