title: Multi column indexes uuid and created_at is not used
body: <p>With a multi column index, it seems like the indexes are not take into consideration, when i do a WHERE or a ORDER BY.<br />
  On an example table for 100 users</p>
  <pre><code>create table users (
    id uuid default uuid_generate_v4() not null constraint users_pkey primary key,
    created_at timestamp default CURRENT_TIMESTAMP
  );
  create index users_id_created_at_idx on users (id desc, created_at desc);
  </code></pre>
  <p>This is the test:</p>
  <pre><code>EXPLAIN(ANALYZE, VERBOSE, BUFFERS)
  SELECT id, created_at
  FROM users
  ORDER BY id DESC, created_at DESC;
  
  Sort  (cost=10.63..10.68 rows=20 width=24) (actual time=1.821..2.676 rows=100 loops=1)
    Output: id, created_at&quot;
    Sort Key: users.id DESC, users.created_at DESC&quot;
    Sort Method: quicksort  Memory: 32kB
    Buffers: shared hit=3
    -&gt;  Seq Scan on public.users  (cost=0.00..10.20 rows=20 width=24) (actual time=0.018..0.861 rows=100 loops=1)
          Output: id, created_at&quot;
          Buffers: shared hit=3
  Planning Time: 0.059 ms
  Execution Time: 3.476 ms
  
  EXPLAIN(ANALYZE, VERBOSE, BUFFERS)
  SELECT id, created_at
  FROM users
  WHERE (id, created_at) &lt;= ('fddb1fa4-d68a-460f-a19f-d722fdf60971', '2022-01-21 17:41:05.936547')
  ORDER BY id DESC, created_at DESC;
  
  Sort  (cost=7.78..8.03 rows=99 width=24) (actual time=1.883..2.810 rows=99 loops=1)
    Output: id, created_at&quot;
    Sort Key: users.id DESC, users.created_at DESC&quot;
    Sort Method: quicksort  Memory: 32kB
    Buffers: shared hit=3
    -&gt;  Seq Scan on public.users  (cost=0.00..4.50 rows=99 width=24) (actual time=0.009..0.953 rows=99 loops=1)
          Output: id, created_at&quot;
          Filter: (ROW(users.id, users.created_at) &lt;= ROW('fddb1fa4-d68a-460f-a19f-d722fdf60971'::uuid, '2022-01-21 17:41:05.936547'::timestamp without time zone))&quot;
          Rows Removed by Filter: 1
          Buffers: shared hit=3
  Planning Time: 0.114 ms
  Execution Time: 3.783 ms
  </code></pre>
  <p>I don't get why it is not using the index. Is it because of the date ? The index follow another format ? Is it because of the uuid ? Or the multi column index ?</p>