[Sqlalchemy-tickets] Issue #3668: problem in execute query string with error lazy loading (zzzeek/sqlalchemy)

[Ramin F. C. <iss...@bi...>]

New issue 3668: problem in execute query string with error lazy loading
https://bitbucket.org/zzzeek/sqlalchemy/issues/3668/problem-in-execute-query-string-with-error

Ramin Farajpour Cami:

Hi,

when use this query first i get valid result of query but again i refresh page site i get this error:
```
Parent instance is not bound to a Session; lazy load operation of attribute 'City' cannot proceed
```

this is a my query:


```
#!python

SELECT p.ID AS 'persons_ID', p.FirstName AS 'persons_FirstName', p.LastName AS 'persons_LastName',
                            p.NationalCode AS 'persons_NationalCode', p.CityID AS 'persons_CityID', p.Mobile AS 'persons_Mobile',
                            p.Address AS 'persons_Address', cities_1.ID AS 'cities_1_ID', cities_1.Name AS 'cities_1_Name',
                            cities_1.ParentID AS 'cities_1_ParentID', cities_2.ID AS 'cities_2_ID', cities_2.Name AS 'cities_2_Name',
                            cities_2.ParentID AS 'cities_2_ParentID' , cast(@row := @row + 1 as unsigned) as 'persons_row_number'

                    FROM Persons p LEFT OUTER JOIN cities AS cities_2 ON cities_2.ID = p.CityID
                    LEFT OUTER JOIN cities AS cities_1 ON cities_1.ID = cities_2.ParentID , (select @row := 0) as init
```
execute query :

```
#!python

 lst = ses.query(Persons).options(joinedload('City')).from_statement(query).all()
```

model :

```
#!python
class Persons(Base):


        __tablename__ = 'persons'

        ID = Column(Integer, primary_key=True)
        FirstName = Column(String(50))
        LastName = Column(String(100))
        NationalCode = Column(String(10))
        CityID = Column(Integer, ForeignKey('cities.ID'))
        Mobile = Column(String(10))
        Address = Column(String(10))

        City = relationship("Cities",lazy="joined",join_depth=2, uselist=False)

        CitiesModel = Cities()

        ProvinceID = None

        HashID = None
        row_number = None


```



Responsible: zzzeek