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?

Dmitry Shevchenko

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

As suggested by "Dmitry Shevchenko" you can run sqlsequencereset to solve your problem.

You can execute the SQL query generated by sqlsequencereset from within python in this way (using the default database):

from django.core.management.color import no_style
from django.db import connection

from myapps.models import MyModel1, MyModel2


sequence_sql = connection.ops.sequence_reset_sql(no_style(), [MyModel1, MyModel2])
with connection.cursor() as cursor:
    for sql in sequence_sql:
        cursor.execute(sql)

I tested this code with Python3.6, Django 2.0 and PostgreSQL 10.

Here's a short snippet to reset all sequences in Django 1.9+ (based on http://djangosnippets.org/snippets/2774/) and compatible with Python 3:

import os
from io import StringIO

os.environ['DJANGO_COLORS'] = 'nocolor'

from django.core.management import call_command
from django.apps import apps
from django.db import connection

commands = StringIO()
cursor = connection.cursor()

for app in apps.get_app_configs():
    label = app.label
    call_command('sqlsequencereset', label, stdout=commands)

cursor.execute(commands.getvalue())

PostgreSQL Command: ALTER SEQUENCE app_model_id_seq RESTART WITH 1

select setval('django_comments_id_seq', 12345);

This snippet Run sqlsequencereset on all apps reset all IDs of all Empty Models

来源：https://stackoverflow.com/questions/14589634/how-to-reset-the-sequence-for-ids-on-postgresql-tables

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django

postgresql