How to reset the sequence for IDs on PostgreSQL tables

I recently imported a lot of data from an old database into a new Postgresql database as the basis for models in a new Django site.

I used the IDs from the old database (as rows in various tables refer to each other), but they aren't all sequential - there are often large gaps.

I've noticed that when I add a new object via the Django app, then it has been using IDs starting from 1, which hasn't been a problem so far as there were no rows with very low IDs.

But once it reaches the first row of legacy data, then postgres obviously complains:

ERROR:  duplicate key value violates unique constraint "django_comments_pkey"
DETAIL:  Key (id)=(25) already exists.

Looking at the table descriptions I'm guessing I need to reset some kind of sequence on each table:

                                      Table "public.django_comments"
     Column      |           Type           |                          Modifiers                           
-----------------+--------------------------+--------------------------------------------------------------
 id              | integer                  | not null default nextval('django_comments_id_seq'::regclass)
...

What do I need to do to reset that sequence, so that new rows are added with IDs higher than the current maximum ID?

Solution

Run sqlsequencereset and it'll print all the reset commands you need.