[Sqlalchemy-tickets] Issue #3963: aliased vs. non-aliased specificity in loader options on lazy load (zzzeek/sqlalchemy)

[Michael B. <iss...@bi...>]

New issue 3963: aliased vs. non-aliased specificity in loader options on lazy load
https://bitbucket.org/zzzeek/sqlalchemy/issues/3963/aliased-vs-non-aliased-specificity-in

Michael Bayer:

all of these cases emit eager load for B.cs when they are specified as lazyload:


```
#!python

from sqlalchemy import *
from sqlalchemy.orm import *
from sqlalchemy.ext.declarative import declarative_base

Base = declarative_base()


class A(Base):
    __tablename__ = 'a'
    id = Column(Integer, primary_key=True)
    bs = relationship("B")

class B(Base):
    __tablename__ = 'b'
    id = Column(Integer, primary_key=True)
    a_id = Column(ForeignKey('a.id'))
    cs = relationship("C")

class C(Base):
    __tablename__ = 'c'
    id = Column(Integer, primary_key=True)
    b_id = Column(ForeignKey('b.id'))

e = create_engine("sqlite://", echo=True)
Base.metadata.create_all(e)

s = Session(e)
s.add(A(bs=[B(cs=[C()])]))
s.add(A())
s.commit()
s.close()

aa = aliased(A)
q = s.query(aa, A).filter(aa.id == 1).filter(A.id == 2).options(joinedload(A.bs).joinedload(B.cs))
for a, real_a in q:
    for b in a.bs:
        # was eager loaded, when should lazy load
        for c in b.cs:
            print c


s.close()

print "--------------------------------"

aa = aliased(A)
q = s.query(aa, A).filter(aa.id == 1).filter(A.id == 2).options(defaultload(A.bs).joinedload(B.cs))
for a, real_a in q:
    for b in a.bs:
        # was eager loaded, when should lazy load
        for c in b.cs:
            print c


s.close()

print "--------------------------------"

aa = aliased(A)
q = s.query(A, aa).filter(A.id == 1).filter(aa.id == 2).options(defaultload(aa.bs).joinedload(B.cs))
for a, real_a in q:
    for b in a.bs:
        # was eager loaded, when should lazy load
        for c in b.cs:
            print c
```


_chop_path is important here, this fixes:

```
#!diff


diff --git a/lib/sqlalchemy/orm/strategy_options.py b/lib/sqlalchemy/orm/strategy_options.py
index bae2b73..60ed2be 100644
--- a/lib/sqlalchemy/orm/strategy_options.py
+++ b/lib/sqlalchemy/orm/strategy_options.py
@@ -376,7 +376,8 @@ class _UnboundLoad(Load):
                         _WILDCARD_TOKEN,) and c_token != p_prop.key:
                     return None
             elif isinstance(c_token, PropComparator):
-                if c_token.property is not p_prop:
+                if c_token.property is not p_prop or \
+                        c_token._parententity is not p_mapper:
                     return None
         else:
             i += 1

```