我一直在 Django 中开发一个应用程序。首先，为简单起见，我一直使用 sqlite3 作为数据库。
但是，一旦我迁移到 PostgreSQL，我就遇到了一个问题：一旦我清除了一个表，主键就不会重置。
这个应用程序是一个长时间（几周）玩的游戏。因此，每次新游戏开始时，都会从数据库中清除所有数据，然后添加新的随机数据。
我希望能够在1每次清理/重建游戏时使用主键“重新开始”。
代码仍然按原样工作，但整数是描述游戏中对象的一种非常自然的方式。我希望每场新游戏都从 1 开始，而不是从上一场比赛结束的地方开始。
如何重置 PostgreSQL 中的主键计数器？请记住，我不需要保留表中的数据，因为无论如何我都会将其清除。
在您的应用程序目录中尝试以下操作：
python manage.py help sqlsequencereset
像这样将它通过管道传输到 psql 中以实际运行重置：
python manage.py sqlsequencereset myapp1 myapp2 | psql
编辑：这是我的一张表上此命令的输出示例：
BEGIN;
SELECT setval('"project_row_id_seq"', coalesce(max("id"), 1), max("id") IS NOT null) FROM "project_row";
COMMIT;
正如“Van Gale”所建议的那样，您可以获得解决问题的命令sqlsequencereset。
或者
sqlsequencereset您可以通过这种方式执行从 python 中生成的 SQL 查询（使用默认数据库）：
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)
我用Python3.6、Django 2.0和PostgreSQL 10测试了这段代码。
如果您执行原始 sql，可以这样做：
ALTER SEQUENCE youApp_id_seq RESTART WITH 1;
文档： http ://www.postgresql.org/docs/8.2/static/sql-altersequence.html
我将自动增量主键视为数据库记录的纯粹内部标识符，我不喜欢将它们暴露给用户。诚然，将它们用作 URL 的一部分是一种常见的设计，但即使存在 slug 或其他标识符也感觉更合适。
如果您不想手动抓取您需要的应用程序，或者如果您有一系列不同的数据库，此命令将从settings.py动态收集所有连接并重置序列。
要运行使用：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)