我在 flask-sqlalchemy 中有一个查询，filter 表现得很奇怪:
q.filter(Transaction.transaction_id == ReconciledTransaction.safe_withdraw_id).all()
它工作正常，但是:
q.filter(Transaction.transaction_id != ReconciledTransaction.safe_withdraw_id).all()
无法正常工作!似乎是什么问题？
UPD
我的模型:
协调交易模型:
class ReconciledTransactionModel(db.Model):
"""Reconciled Transaction model"""
__tablename__ = 'ReconciledTransaction'
id = db.Column('id', db.Integer, primary_key=True, nullable=False)
balance_entry_id = db.Column('BalanceEntry_id', db.Integer, db.ForeignKey("BalanceEntry.id"), nullable=False)
safe_withdraw_id = db.Column('Transaction_id', db.String, nullable=False)
datetime = db.Column('datetime', db.Date(), nullable=False)
balance_entry_amount = db.Column('BalanceEntry_amount', db.Float)
reconciled_amount = db.Column('ReconciledAmount', db.Float)
currency = db.Column('currency', db.String)
reconciliation_status = db.Column('reconciliation_status', db.String, nullable=False)
status_code = db.Column('status_code', db.Integer, nullable=False)
交易模型:
class TransactionModel(db.Model):
"""Transaction SA model."""
__tablename__ = 'Transaction'
id = db.Column('id', db.Integer, primary_key=True)
till_id = db.Column('Till_id', db.Integer, db.ForeignKey("Till.id"),
nullable=False)
till = relationship("Till", foreign_keys=[till_id], backref="transactions", enable_typechecks=False)
establishment_id = db.Column('Establishment_id', db.Integer,
db.ForeignKey("Establishment.id"),
nullable=False)
establishment = relationship("Establishment",
foreign_keys=[establishment_id],
backref="transactions",
enable_typechecks=False)
employee_id = db.Column('Employee_id', db.Integer,
db.ForeignKey("Employee.id"),
nullable=False)
employee = relationship("Employee",
foreign_keys=[employee_id],
backref="transactions",
enable_typechecks=False)
local_time = db.Column('local_time', db.DateTime, nullable=False)
create_time = db.Column('create_time', db.TIMESTAMP(timezone=True),
nullable=False)
send_time = db.Column('send_time', db.TIMESTAMP(timezone=True),
nullable=False)
receive_time = db.Column('receive_time', db.TIMESTAMP(timezone=True),
nullable=False)
total_value = db.Column('total_value', db.Integer, nullable=False)
amount = db.Column('amount', db.Float, nullable=False)
discrepancy = db.Column('discrepancy', db.Float, nullable=False)
type = db.Column('type', db.Enum('shift',
'payment',
'skimming',
'withdraw',
'refund',
'till',
'till_deposit',
'safe_deposit',
'safe_withdraw',
'till_reset',
name='transaction_type'),
nullable=False)
status = db.Column('status',
db.Enum('start', 'end', name='transaction_status'),
nullable=False)
receipt_id = db.Column('receipt_id', db.String(32), server_default=None)
transaction_id = db.Column('transaction_id', db.String(32),
server_default=None)
parent_transaction = db.Column('parent_transaction', db.String(32),
server_default=None)
discrepancy_reason = db.Column('discrepancy_reason', db.String(1024))
resolve_discrepancy_reason = db.Column('resolve_discrepancy_reason',
db.String(1024))
accounted = db.Column('accounted', db.Boolean, default=False)
这是我的查询:
_transactions = db.session.query(Transaction,
status_sq.c.count,
end_transaction_sq.c.discrepancy,
end_transaction_sq.c.discrepancy_reason,
end_transaction_sq.c.resolve_discrepancy_reason,
end_transaction_sq.c.amount,
). \
filter(Transaction.establishment_id.in_(store_ids)). \
filter(Transaction.amount != 0). \
filter_by(status='start')
transactions = _transactions. \
filter(Transaction.type.in_(transaction_types)). \
outerjoin(status_sq,
Transaction.transaction_id == status_sq.c.transaction_id). \
outerjoin(end_transaction_sq,
Transaction.transaction_id == end_transaction_sq.c.transaction_id)
# check possible values for sorting and pages
if sort_field not in allowed_sort_fields:
sort_field = Transaction.default_sort_field
if sort_dir not in (ASCENDING, DESCENDING):
sort_dir = Transaction.default_sort_dir
if per_page > 100: # hard limit
per_page = Transaction.default_per_page
if sort_dir == ASCENDING:
order = allowed_sort_fields[sort_field].desc()
else:
order = allowed_sort_fields[sort_field].desc()
q = transactions.\
join(Establishment).\
join(Employee, Transaction.employee_id == Employee.id). \
outerjoin(Currency). \
group_by(Transaction,
status_sq.c.count,
end_transaction_sq.c.discrepancy,
end_transaction_sq.c.discrepancy_reason,
end_transaction_sq.c.resolve_discrepancy_reason,
end_transaction_sq.c.amount,
allowed_sort_fields[sort_field]).\
order_by(order)
items = q.filter(Transaction.transaction_id == ReconciledTransaction.safe_withdraw_id).limit(per_page).offset((page - 1) * per_page).all()
“无法正常工作”意味着在第二种情况下(当我放置 != 时，并且只想进行不在 ReconciledTransaction 表中的交易)过滤器被忽略，但是当过滤器包含==，一切正常(我只有匹配的交易)。
最佳答案
当您使用这样的查询时:
q = db.session.query(Transaction). \
filter(Transaction.transaction_id != ReconciledTransaction.safe_withdraw_id)
它转换成 SQL 查询:
SELECT Transaction.* FROM Transaction, ReconciledTransaction
WHERE Transaction.transaction_id != ReconciledTransaction.safe_withdraw_id
这意味着您将获得所有 Transaction 行以及所有 ReconciledTransaction 行，但具有匹配 ID 的行除外。
如果您需要获取不在 ReconciledTransaction 表中的所有 Transaction 对象，您可以先获取所有 ReconciledTransaction id:
r_query = db.session.query(ReconciledTransaction.safe_withdraw_id). \
group_by(ReconciledTransaction.safe_withdraw_id)
r_ids = [x[0] for x in r_query]
然后在您的交易查询中使用 NOT IN 过滤器:
q = q.filter(Transaction.transaction_id.notin_(r_ids))
或者您可以使用子查询:
q = q.filter(Transaction.transaction_id.notin_(
db.session.query(ReconciledTransaction.safe_withdraw_id)
))
编辑:正如 Ilja Everilä 所说，不存在运算符性能 might be better比不在。 SQLAlchemy 查询将如下所示:
q = q.filter(~session.query(ReconciledTransaction). \
filter(ReconciledTransaction.safe_withdraw_id == Transaction.id).exists())
关于python - flask-sqlalchemy 中的奇怪过滤器行为，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/46440663/