Django reset auto-increment pk/id field for production

Question:

(I’m new to Django, Python, and Postgresql) I’ve been adding and deleting data in my development and noticed that the pk keeps adding up and never reset to 1 even if I delete all the models. Is it possible to reset the pk to start from 1 before I push this up to the production? Is it a good idea to do that?

Asked By: Vicky Leong

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Answers:

You can reset model id sequence using sqlsequencereset command

python manage.py sqlsequencereset myapp1 myapp2 myapp3| psql

If you want to read the generated sql command, just execute that command without pipe it to psql.

python manage.py sqlsequencereset myapp1 myapp2 myapp3

You need use this command over your production database. But, as @knbk mentioned, if your production database is new, you don’t need to reset id sequences.

Answered By: levi

You could generate a command that gathers all of the applications in your system and runs a dynamically generated reset statement for each table, while also dynamically gathering the PK column names for each table you loop over in the event you didn’t name them all the same value.

To run: python manage.py reset_sequences

import psycopg2
from django.conf import settings
from django.core.management.base import BaseCommand
from django.db import connections


def dictfetchall(cursor):
    """Return all rows from a cursor as a dict"""
    columns = [col[0] for col in cursor.description]
    return [
        dict(zip(columns, row))
        for row in cursor.fetchall()
    ]


class Command(BaseCommand):
    help = "Resets sequencing errors in Postgres which normally occur due to importing/restoring a DB"

    def handle(self, *args, **options):
        # loop over all databases in system to figure out the tables that need to be reset
        for name_to_use_for_connection, connection_settings in settings.DATABASES.items():
            db_name = connection_settings['NAME']
            host = connection_settings['HOST']
            user = connection_settings['USER']
            port = connection_settings['PORT']
            password = connection_settings['PASSWORD']

            # connect to this specific DB
            conn_str = f"host={host} port={port} user={user} password={password}"

            conn = psycopg2.connect(conn_str)
            conn.autocommit = True

            select_all_table_statement = f"""SELECT *
                                    FROM information_schema.tables
                                    WHERE table_schema = 'public'
                                    ORDER BY table_name;
                                """
            # just a visual representation of where we are
            print('-' * 20, db_name)
            try:
                not_reset_tables = list()
                # use the specific name for the DB
                with connections[name_to_use_for_connection].cursor() as cursor:
                    # using the current db as the cursor connection
                    cursor.execute(select_all_table_statement)
                    rows = dictfetchall(cursor)
                    # will loop over table names in the connected DB
                    for row in rows:
                        find_pk_statement = f"""
                            SELECT k.COLUMN_NAME
                            FROM information_schema.table_constraints t
                            LEFT JOIN information_schema.key_column_usage k
                            USING(constraint_name,table_schema,table_name)
                            WHERE t.constraint_type='PRIMARY KEY'
                                AND t.table_name='{row['table_name']}';
                        """
                        cursor.execute(find_pk_statement)
                        pk_column_names = dictfetchall(cursor)
                        for pk_dict in pk_column_names:
                            column_name = pk_dict['column_name']

                        # time to build the reset sequence command for each table
                        # taken from django: https://docs.djangoproject.com/en/3.0/ref/django-admin/#sqlsequencereset
                        # example: SELECT setval(pg_get_serial_sequence('"[TABLE]"','id'), coalesce(max("id"), 1), max("id") IS NOT null) FROM "[TABLE]";
                        try:
                            reset_statement = f"""SELECT setval(pg_get_serial_sequence('"{row['table_name']}"','{column_name}'), 
                                                    coalesce(max("{column_name}"), 1), max("{column_name}") IS NOT null) FROM "{row['table_name']}" """
                            cursor.execute(reset_statement)
                            return_values = dictfetchall(cursor)
                            # will be 1 row
                            for value in return_values:
                                print(f"Sequence reset to {value['setval']} for {row['table_name']}")
                        except Exception as ex:
                            # will only fail if PK is not an integer...
                            # currently in my system this is from django.contrib.sessions
                            not_reset_tables.append(f"{row['table_name']} not reset")

            except psycopg2.Error as ex:
                raise SystemExit(f'Error: {ex}')

            conn.close()
            print('-' * 5, ' ALL ERRORS ', '-' * 5)
            for item_statement in not_reset_tables:
                # shows which tables produced errors, so far I have only
                # seen this with PK's that are not integers because of the MAX() method
                print(item_statement)

            # just a visual representation of where we are
            print('-' * 20, db_name)



Answered By: ViaTech

Alternative to sqlsequencereset: Update directly with SQLite

Development Environnement with the default db.sqlite3 database

I was struggling for some time trying the answers given here and I kept receiving :

python manage.py sqlsequencereset AppName
>> No sequences found.

The easiest workaround for me was to directly update my SQLite database (i run my app locally):

# Open your database
sqlite3 db.sqlite3

And, in the SQLite prompt:

UPDATE sqlite_sequence SET seq = 0 WHERE sqlite_sequence.name = "<AppName_ModelName>";

I set the value to zero so it starts with id = 1.

EDIT : This is my very first post, please let me know if I should improve the format!

Answered By: Michael Debétaz

i know its very old post but you can make an id reseter in django (just an idea in my mind) lets say i have a model called (Records):

def index_reset(request):
    records = Records.objects.all()
    index = 1
    for record in records:
        old_record = Records.objects.get(id=record.id)
        record.id = index
        record.save()
        old_record.delete()
        index = index + 1
    return redirect("/")

the problem is you have to take all the records ….the more you have the slower and more resource

Answered By: abdullah