title: Table sequence id not incrementing after applying alembic migration
body: <p>I am facing a weird problem using alembic migration. I am using Postgres as DB.</p>
  
  <p>I have written an alembic revision where I am inserting some data in a table(There is already some data in the table before migration).</p>
  
  <p>The issue is the migration runs successfully and inserted the data in the table. But after this when I am calling an api and trying to insert a new row I get some error, because table seq_id is not incremented.</p>
  
  <pre><code>ERROR:__name__:Failed to create a duplicate entry: (psycopg2.IntegrityError) duplicate key value violates unique constraint "user_pkey"
  DETAIL:  Key (id)=(9) already exists.
   [SQL: 'INSERT INTO user (id, name, age, number) VALUES (%(id)s, %(name)s, %(age)s, %(number)s) RETURNING id'] [parameters: {'number': None, 'id': 9, 'name': 'something', 'age': 12}]
  </code></pre>
  
  <p>Let's take an example: </p>
  
  <p>I have table "User" which already have 10 rows, now using alembic migration I am inserting two rows so now there are 12 rows. Ideally, it should update the sequence_id too, but seq_id is still at 10.</p>
  
  <p>No using an api I am inserting on more row which it will try to add at id 11 and will give the above error. If I try this api two more times then it will be a success because it will increment the seq_id every time.</p>
  
  <p>This is happening only after applying alembic migration, else it is working fine.</p>
  
  <p>Can anyone tell me what I am doing wrong, did I miss any config, why the sequence id is not incrementing while applying migration?</p>
  
  <p>Thanks in advance!</p>