[Sqlalchemy-tickets] Issue #4363: select from clause change when I update version from 1.2.12 to 1.2.13 (zzzeek/sqlalchemy)

[大易归真 <iss...@bi...>]

New issue 4363: select from clause change when I update version from 1.2.12 to 1.2.13
https://bitbucket.org/zzzeek/sqlalchemy/issues/4363/select-from-clause-change-when-i-update

大易归真:

My query code is:
```
funcs = aliased(Function)
mapping = db.session.query(FunctionMapping).get(1)
foreign_funcs = mapping.peers.join(ForeignFunction.functions).join(funcs)
```
When use version 1.2.12:

The SQL is

```
SELECT ... 
FROM foreign_function_set, foreign_function INNER JOIN foreign_function_map AS foreign_function_map_1 ON foreign_function.id = foreign_function_map_1.foreign_function_id INNER JOIN function ON function.id = foreign_function_map_1.function_id INNER JOIN function AS function_2 ON function.id = function_2.parent_id AND function_2.id = function.parent_id LEFT OUTER JOIN (foreign_function_map AS foreign_function_map_2 INNER JOIN function AS function_1 ON function_1.id = foreign_function_map_2.function_id) ON foreign_function.id = foreign_function_map_2.foreign_function_id
```

When I update sqlalchemy version to 1.2.13, The SQL is:

```
SELECT ...
FROM foreign_function_set INNER JOIN `function` AS function_2 ON function_2.id = `function`.id OR function_2.function_id = `function`.id OR function_2.function_group_id = `function`.id, foreign_function INNER JOIN foreign_function_map AS foreign_function_map_1 ON foreign_function.id = foreign_function_map_1.foreign_function_id INNER JOIN `function` ON `function`.id = foreign_function_map_1.function_id LEFT OUTER JOIN (foreign_function_map AS foreign_function_map_2 INNER JOIN `function` AS function_1 ON function_1.id = foreign_function_map_2.function_id) ON foreign_function.id = foreign_function_map_2.foreign_function_id
```

The program raise error `u"Unknown column 'function.id' in 'on clause'"`

I find 1.2.13 add `_from_obj ` to query, but don't understand how this attribute change SQL?


This is class and secondary defina

```
#!python

class Function(db.Model):
    id = db.Column(db.SmallInteger, autoincrement=True, primary_key=True)

    function_id = db.Column(db.SmallInteger)
    function_group_id = db.Column(db.SmallInteger)

    parent_id = db.Column(db.SmallInteger, db.ForeignKey('function.id'))
    children = db.relationship(
        'Function', lazy='dynamic', backref=db.backref(
             'parent', remote_side=[id]))


foreign_function_map = db.Table('foreign_function_map', db.Column(
    'foreign_function_id', db.SmallInteger, db.ForeignKey(
        'foreign_function.id', ondelete='CASCADE'), primary_key=True
    ), db.Column(
        'function_id', db.SmallInteger, db.ForeignKey('function.id'),
        primary_key=True
    ))


class ForeignFunction(db.Model):
    id = db.Column(db.SmallInteger, autoincrement=True, primary_key=True)
    functions = db.relationship(
        'Function', secondary=foreign_function_map, lazy='joined')


foreign_function_set = db.Table('foreign_function_set', db.Column(
    'function_mapping_id', db.SmallInteger, db.ForeignKey(
        'function_mapping.id'), primary_key=True), db.Column(
    'foreign_function_id', db.SmallInteger, db.ForeignKey(
        'foreign_function.id'), primary_key=True))


class FunctionMapping(db.Model):
    id = db.Column(db.SmallInteger, autoincrement=True, primary_key=True)
    key = db.Column(db.String(20), index=True, unique=True)
    peers = db.relationship(
        'ForeignFunction', secondary=foreign_function_set, lazy='dynamic',
        backref=db.backref('site'))
```