Python SQLAlchemy在测试期间自动恢复增量（pytest）

我在

conftest.py

@pytest.fixture(scope='function')
def db_session(db, request):
    """Creates a new database session for a test."""
    engine = create_engine(DefaultConfig.SQLALCHEMY_DATABASE_URI, connect_args={"options": "-c timezone=utc"})
    DbSession = sessionmaker(bind=engine)
    session = DbSession()

    connection = engine.connect()
    transaction = connection.begin()

    options = dict(bind=connection, binds={})
    session = db.create_scoped_session(options=options)

    db.session = session

    yield session

    transaction.rollback()
    connection.close()
    session.remove()

import pytest
from package.model import Project

def test_create_project(db_session):
    project = Project(project_name="Test_Project")

    db_session.add(project)
    db_session.commit()

    assert project.project_id > 0
    assert project.project_id == 65 # supposed to be the next auto-increment value
    assert db_session.query(Project).filter_by(project_name="Test_Project").first() != None

在我的测试脚本中

test\u project.py

@pytest.fixture(scope='function')
def db_session(db, request):
    """Creates a new database session for a test."""
    engine = create_engine(DefaultConfig.SQLALCHEMY_DATABASE_URI, connect_args={"options": "-c timezone=utc"})
    DbSession = sessionmaker(bind=engine)
    session = DbSession()

    connection = engine.connect()
    transaction = connection.begin()

    options = dict(bind=connection, binds={})
    session = db.create_scoped_session(options=options)

    db.session = session

    yield session

    transaction.rollback()
    connection.close()
    session.remove()

import pytest
from package.model import Project

def test_create_project(db_session):
    project = Project(project_name="Test_Project")

    db_session.add(project)
    db_session.commit()

    assert project.project_id > 0
    assert project.project_id == 65 # supposed to be the next auto-increment value
    assert db_session.query(Project).filter_by(project_name="Test_Project").first() != None

每次运行测试时，自动递增的主键都会增加。即使我使用了

db_session

fixture，主键序列也不会回滚

我还尝试在测试之间调用

db\u session.begin\u nested（）

和

db\u session.rollback（）

，但主键仍然会递增

def test_create_project(db_session):
    db_session.begin_nested()
    project = Project(project_name="Test_Project")

    db_session.add(project)
    db_session.commit()

    assert project.project_id > 0
    assert project.project_id == 65
    assert db_session.query(Project).filter_by(project_name="Test_Project").first() != None
    db_session.rollback()

测试后如何恢复自动增量值

环境

• 数据库：PostgreSQL 9.6.5
• 烧瓶0.12.2
• SQLAlchemy 1.1.12

---

使用sqlalchemy是不可能的。但是，您可以在所需的起点更改并重新启动序列。默认情况下，postgresql将序列命名为

\uu seq

。检查您的模式以找出序列名称。这是改变序列所必需的
下面是一个小脚本来说明这一点：

CREATE TABLE test(col1 SERIAL PRIMARY KEY, val TEXT);
INSERT INTO test (val) VALUES ('abc'), ('def'), ('ghi');
SELECT * FROM test;
-- output
1   abc
2   def
3   ghi

DELETE FROM test WHERE col1 = 3;
SELECT * FROM test;
-- output
1   abc
2   def

-- now alter the sequence so that the next insert gets value 3 in col1
ALTER SEQUENCE test_col1_seq START 3 RESTART;
INSERT INTO test (val) VALUES ('xyz');
SELECT * FROM test;
-- output
1   abc
2   def
3   xyz