我有以下代码,我想补充一下:
def add_electricity_reading(
*, period_usage, period_started_at, is_estimated, customer_pk
):
from sqlalchemy.dialects.postgresql import insert
values = dict(
customer_pk=customer_pk,
period_usage=period_usage,
period_started_at=period_started_at,
is_estimated=is_estimated,
)
insert_stmt = insert(ElectricityMeterReading).values(**values)
do_update_stmt = insert_stmt.on_conflict_do_update(
constraint=ElectricityMeterReading.__table_args__[0].name,
set_=dict(
period_usage=period_usage,
period_started_at=period_started_at,
is_estimated=is_estimated,
)
)
conn = DBSession.connection()
conn.execute(do_update_stmt)
return DBSession.query(ElectricityMeterReading).filter_by(**dict(
period_usage=period_usage,
period_started_at=period_started_at,
customer_pk=customer_pk,
is_estimated=is_estimated,
)).one()
def test_updates_existing_record_for_started_at_if_already_exists():
started_at = datetime.now(timezone.utc)
existing = add_electricity_reading(
period_usage=0.102,
customer_pk=customer.pk,
period_started_at=started_at,
is_estimated=True,
)
started_at = existing.period_started_at
reading = add_electricity_reading(
period_usage=0.200,
customer_pk=customer.pk,
period_started_at=started_at,
is_estimated=True,
)
# existing record was updated
assert reading.period_usage == 0.200
assert reading.id == existing.id
在我的测试中,我添加了一个带有cc*>的现有记录,然后再次执行查询,但是改为
period_usage=0.102
。当底部的最终查询返回记录时,period_usage仍然是0.102。知道为什么会这样吗?
最佳答案
这种行为在"What does the Session do?"下的“会话基础”中解释,会话包含对它在一个名为identity map的结构中加载的对象的引用,因此确保每个会话期间的每个主键值只有1个唯一的对象存在。您可以在自己的代码中使用以下断言来验证这一点:
assert existing is reading
您正在执行的Coreinsert(或update)语句不会像
Query.update()
那样使会话与数据库中发生的更改保持同步。为了获取新值,您可以expire唯一对象的ORM加载状态:DBSession.expire(existing) # or reading, does not matter
# existing record was updated
assert reading.period_usage == 0.200
assert reading.id == existing.id
关于python - SQLAlchemy'on_conflict_do_update'不更新,我们在Stack Overflow上找到一个类似的问题:https://stackoverflow.com/questions/52947219/