That's fine but you should probably use a normal @property for that, unless you are still making use of a separate "expression" portion.
On Fri, Jun 8, 2018, 8:04 PM HP3 <henddher.pedr...@gmail.com> wrote: > I ended up settling for this: > > @hybrid_property > > def ancestors(self): > > session = inspect(self).session > > cte = session.query(P2B) \ > > .filter(P2B.id == self.id) \ > > .cte(name='cte', recursive=True) > > cte = cte.union( > > session.query(P2B) > > .filter(P2B.id == cte.c.parent_id) > > ) > > return session.query(cte).all() > > And each time I call child.ancestors, the SQL CTE RECURSIVE is issued (of > course!?) > > Thanks again for all your help Mike! > > On Friday, June 8, 2018 at 6:39:05 PM UTC-5, HP3 wrote: >> >> BTW, the solution of `.params(child_id=child_id)` you provided worked >> perfectly - forgot to mentioned earlier. >> It issued the recursive CTE I wanted. >> >> I still need to ponder if I can simply live with a plain select().cte() >> within a vanilla method or @hybrid_property or @hybrid_method, all except >> @hybrid_property.expression as in the latter the "caller" would need to >> remember to bind `child_id` explicitly and forfeit the usage of `filter( >> ancs.c.id==child_id)` >> >> Thank you very much again Mike !!!! >> >> On Friday, June 8, 2018 at 6:06:54 PM UTC-5, Mike Bayer wrote: >>> >>> On Fri, Jun 8, 2018 at 6:59 PM, HP3 <henddher...@gmail.com> wrote: >>> > :( >>> > >>> > Basically, I was trying to prevent the SQL Select for each >>> child-to-parent >>> > loop-iteration when navigating the tree from leaf to root because I >>> figured >>> > I could use CTE recursive as @hybrid_property.expression. >>> > >>> > I was trying to take full advantage of @hybrid_property.expression >>> like the >>> > examples in >>> > >>> http://docs.sqlalchemy.org/en/latest/orm/extensions/hybrid.html#join-dependent-relationship-hybrid >>> > and >>> > >>> http://docs.sqlalchemy.org/en/latest/orm/extensions/hybrid.html#module-sqlalchemy.ext.hybrid >>> > The examples show that self/cls is magically chosen depending on the >>> > context. >>> > >>> > Seems like I will end up having *limited* functionality for my >>> > `@hybrid_property.expression` as I would have to pass the extra param >>> > `cls_id` explicitly. >>> > >>> > I was hoping that >>> `dbsession.query(P2B.ancestors).filter(P2B.id==mychildid)` >>> > would automagically bind 'mychildid' to `cls.id` within the >>> > @ancestors.expression. >>> > Perhaps such is possible some other way? >>> >>> a hybrid is just a function to give you a component of SQL. if you >>> want to change the inside of it, then you need to send a parameter on >>> the inside or do a transformation of it. I guess you could run a >>> transform, which is what the lazy loader does, e.g. looks for where >>> something like "cls.id" is and then replaces it but this is very >>> specialized, it wouldn't look any nicer from the calling point of >>> view. >>> >>> >>> >>> >>> > >>> > Another catch is that by issuing the manual CTE, the session would >>> always >>> > issue the SQL and never returned previously loaded ancestors. >>> > >>> > root >>> > / \ >>> > c1 c2 >>> > >>> > c1.ancestors and c2.ancestors will each issue SQL recursive CTE ... >>> right? >>> > >>> > >>> > On Friday, June 8, 2018 at 5:33:08 PM UTC-5, Mike Bayer wrote: >>> >> >>> >> On Fri, Jun 8, 2018 at 5:14 PM, HP3 <henddher...@gmail.com> wrote: >>> >> > Thank you so much Mike >>> >> > >>> >> > >>> >> > I am trying to write @ancestors.expression to produce a SQL like >>> this: >>> >> > >>> >> > WITH RECURSIVE scte(id, parent_id) AS >>> >> > >>> >> > (SELECT p2bases.id AS id, p2bases.parent_id AS parent_id >>> >> > >>> >> > FROM p2bases >>> >> > >>> >> > WHERE p2bases.id = %(id_1)s --- This is the param I need at >>> runtime >>> >> > (cls.id) >>> >> > >>> >> > UNION SELECT p2bases.id AS id, p2bases.parent_id AS parent_id >>> >> > >>> >> > FROM p2bases, scte >>> >> > >>> >> > WHERE p2bases.id = scte.parent_id) >>> >> > >>> >> > SELECT scte.id >>> >> > >>> >> > FROM scte >>> >> >>> >> >>> >> you'd have to put the parameter inside the CTE then, here's one way: >>> >> >>> >> @ancestors.expression >>> >> def ancestors(cls): >>> >> cte = select([P2B.id, P2B.parent_id]) \ >>> >> .where(P2B.id == bindparam("cls_id")) \ >>> >> .cte(name='cte', recursive=True) >>> >> cte = cte.union( >>> >> select([P2B.id, P2B.parent_id]) >>> >> .where(P2B.id == cte.c.parent_id) >>> >> ) >>> >> return cte >>> >> >>> >> >>> >> then you do: >>> >> >>> >> dbsession.query(P2B.ancestors).params(cls_id=child_id).all() >>> >> >>> >> >>> >> but note that you always need to provide params(cls_id=x) in that >>> case. >>> >> >>> >> >>> >> >>> >> > >>> >> > >>> >> > >>> >> > >>> >> > Here is the @hybrid_property.expression >>> >> > >>> >> > @ancestors.expression >>> >> > >>> >> > def ancestors(cls): >>> >> > >>> >> > cte = select([P2B.id, P2B.parent_id]) \ >>> >> > >>> >> > .where(P2B.id == cls.id) \ # <<<<<<< I cannot figure >>> out how >>> >> > make cls.id the param >>> >> > >>> >> > .cte(name='cte', recursive=True) >>> >> > >>> >> > cte = cte.union( >>> >> > >>> >> > select([P2B.id, P2B.parent_id]) >>> >> > >>> >> > .where(P2B.id == cte.c.parent_id) >>> >> > >>> >> > ) >>> >> > >>> >> > return cte >>> >> > >>> >> > >>> >> > I tried alias, aliased and bindparam in multiple ways >>> unsuccessfully. >>> >> > >>> >> > >>> >> > The SQL that is coming out doesn't set the first (cte anchor) WHERE >>> >> > clause >>> >> > with the bound param id_1 (cls.id in the @ancestors.expression). >>> >> > Instead, is the column again? >>> >> > >>> >> > WITH RECURSIVE cte(id, parent_id) AS >>> >> > >>> >> > (SELECT p2bases.id AS id, p2bases.parent_id AS parent_id >>> >> > >>> >> > FROM p2bases >>> >> > >>> >> > WHERE p2bases.id = p2bases.id -- <<<< I can't figure out how to >>> make >>> >> > expr.left 'cls.id' from the @ancestors.expression >>> >> > >>> >> > UNION SELECT p2bases.id AS id, p2bases.parent_id AS parent_id >>> >> > >>> >> > FROM p2bases, cte >>> >> > >>> >> > WHERE p2bases.id = cte.parent_id) >>> >> > >>> >> > SELECT cte.id AS cte_id, cte.parent_id AS cte_parent_id >>> >> > >>> >> > FROM cte >>> >> > >>> >> > WHERE cte.id = %(id_1)s >>> >> > >>> >> > >>> >> > >>> >> > The correct SQL comes out when I do this: >>> >> > >>> >> > scte = select([P2B.id, P2B.parent_id]) \ >>> >> > >>> >> > .where(P2B.id == child_id) \ >>> >> > >>> >> > .cte(name='scte', recursive=True) >>> >> > >>> >> > scte = scte.union( >>> >> > >>> >> > select([P2B.id, P2B.parent_id]).where(P2B.id == >>> >> > scte.c.parent_id)) >>> >> > >>> >> > s = select([scte.c.id]) >>> >> > >>> >> > ancestors = dbsession.execute(s).fetchall() >>> >> > >>> >> > >>> >> > But I don't know how to integrate that into my >>> @ancestors.expression >>> >> > >>> >> > I want `child_id` to get the value of `cls.id` when the >>> @hybrid_property >>> >> > is >>> >> > called for the class. >>> >> > >>> >> > >>> >> > >>> >> > >>> >> > On Friday, June 8, 2018 at 1:48:55 PM UTC-5, Mike Bayer wrote: >>> >> >> >>> >> >> the example is huge can you point out which two queries you'd like >>> to >>> >> >> compare? >>> >> >> >>> >> >> this: >>> >> >> cte = dbsession.query(P2B.id, P2B.parent_id) \ >>> >> >> .filter(P2B.id == child_id) \ >>> >> >> .cte(name='cte', recursive=True) >>> >> >> cte = cte.union( >>> >> >> dbsession.query(P2B.id, P2B.parent_id).filter( >>> >> >> P2B.id == cte.c.parent_id)) >>> >> >> cteids = dbsession.query(cte.c.id) >>> >> >> ancestors = >>> >> >> dbsession.query(P2B).filter(P2B.id.in_(cteids)).all()[1:] >>> >> >> >>> >> >> >>> >> >> and this? >>> >> >> >>> >> >> ancestors = dbsession.query( >>> >> >> P2B.ancestors).filter(P2B.id == child_id).all() # >>> <<<< >>> >> >> child_id IS NEVER USED IN EXPRESSION >>> >> >> >>> >> >> >>> >> >> >>> >> >> it might surprise you to know I barely follow what these queries >>> are >>> >> >> returning for you, I just look very briefly to get the desired >>> syntax >>> >> >> right, so a simple "here's teh code hre's the SQL" is best >>> >> >> >>> >> >> >>> >> >> >>> >> >> On Fri, Jun 8, 2018 at 2:44 PM, HP3 <henddher...@gmail.com> >>> wrote: >>> >> >> > Ahhhh!!! Makes perfect sense! >>> >> >> > >>> >> >> > But there is something still amiss ... >>> >> >> > The last 2 assertions are triggering because the query is >>> returning a >>> >> >> > single >>> >> >> > ancestor (self) instead of the whole recursive list. >>> >> >> > >>> >> >> > See the plain CTE and the @hybrid_property.expression CTE: The >>> where >>> >> >> > clauses >>> >> >> > are still different :( >>> >> >> > (and hence the output) >>> >> >> > >>> >> >> > Are my @hybrid_property.expressions incorrectly declared? >>> >> >> > >>> >> >> > >>> >> >> > CTE ---------------------------------------- >>> >> >> > >>> >> >> > 2018-06-08 13:14:44,144 INFO sqlalchemy.engine.base.Engine BEGIN >>> >> >> > (implicit) >>> >> >> > >>> >> >> > 2018-06-08 13:14:44,145 INFO sqlalchemy.engine.base.Engine WITH >>> >> >> > RECURSIVE >>> >> >> > cte(id, parent_id) AS >>> >> >> > >>> >> >> > (SELECT p2bases.id AS id, p2bases.parent_id AS parent_id >>> >> >> > >>> >> >> > FROM p2bases >>> >> >> > >>> >> >> > WHERE p2bases.id = %(id_1)s UNION SELECT p2bases.id AS >>> p2bases_id, >>> >> >> > p2bases.parent_id AS p2bases_parent_id >>> >> >> > >>> >> >> > FROM p2bases, cte >>> >> >> > >>> >> >> > WHERE p2bases.id = cte.parent_id) >>> >> >> > >>> >> >> > SELECT p2bases.id AS p2bases_id, p2bases.uuid AS p2bases_uuid, >>> >> >> > p2bases.classname AS p2bases_classname, p2bases.position AS >>> >> >> > p2bases_position, p2bases.extras AS p2bases_extras, p2bases.val >>> AS >>> >> >> > p2bases_val, p2bases.time AS p2bases_time, p2bases.parent_id AS >>> >> >> > p2bases_parent_id >>> >> >> > >>> >> >> > FROM p2bases >>> >> >> > >>> >> >> > WHERE p2bases.id IN (SELECT cte.id AS cte_id >>> >> >> > >>> >> >> > FROM cte) >>> >> >> > >>> >> >> > 2018-06-08 13:14:44,146 INFO sqlalchemy.engine.base.Engine >>> {'id_1': >>> >> >> > 20} >>> >> >> > >>> >> >> > CTE ANCESTORS <__main__.P2Pg object at 0x10bf94be0> >>> >> >> > >>> >> >> > CTE ANCESTORS <__main__.P2An object at 0x10bf9a160> >>> >> >> > >>> >> >> > CTE ANCESTORS <__main__.P2KVP object at 0x10bf9a6a0> >>> >> >> > >>> >> >> > >>> >> >> > >>> >> >> > @hybrid_property.expression ANCESTORS CLS >>> >> >> > ---------------------------------------- >>> >> >> > >>> >> >> > 2018-06-08 13:14:44,181 INFO sqlalchemy.engine.base.Engine WITH >>> >> >> > RECURSIVE >>> >> >> > cte(id, parent_id) AS >>> >> >> > >>> >> >> > (SELECT p2bases.id AS id, p2bases.parent_id AS parent_id >>> >> >> > >>> >> >> > FROM p2bases >>> >> >> > >>> >> >> > WHERE p2bases.id = p2bases.id UNION SELECT p2bases.id AS id, >>> >> >> > p2bases.parent_id AS parent_id >>> >> >> > >>> >> >> > FROM p2bases, cte >>> >> >> > >>> >> >> > WHERE p2bases.id = cte.parent_id) >>> >> >> > >>> >> >> > SELECT cte.id AS cte_id, cte.parent_id AS cte_parent_id >>> >> >> > >>> >> >> > FROM cte >>> >> >> > >>> >> >> > WHERE cte.id = %(id_1)s >>> >> >> > >>> >> >> > 2018-06-08 13:14:44,182 INFO sqlalchemy.engine.base.Engine >>> {'id_1': >>> >> >> > 20} >>> >> >> > >>> >> >> > @hybrid_property.expression ANCESTORS CLS (20, 5) >>> >> >> > >>> >> >> > >>> >> >> > >>> >> >> > >>> >> >> > On Friday, June 8, 2018 at 12:27:28 PM UTC-5, Mike Bayer wrote: >>> >> >> >> >>> >> >> >> On Fri, Jun 8, 2018 at 12:16 PM, HP3 <henddher...@gmail.com> >>> wrote: >>> >> >> >> > Attached the whole file >>> >> >> >> >>> >> >> >> OK, removing all the "zope" stuff as well as all the other >>> queries >>> >> >> >> that aren't noted as failing, I am only looking at this query: >>> >> >> >> >>> >> >> >> ancestors = dbsession.query(P2B.ancestors).filter(P2B.id == >>> >> >> >> child_id).all() # <<<< child_id IS NEVER USED IN EXPRESSION >>> >> >> >> >>> >> >> >> the problem is that you are re-introducing P2B a second time, >>> rather >>> >> >> >> than referring to the columns that your CTE returns, it should >>> be: >>> >> >> >> >>> >> >> >> ansc = P2B.ancestors >>> >> >> >> ancestors = dbsession.query(ansc).filter(ansc.c.id == >>> >> >> >> child_id).all() >>> >> >> >> >>> >> >> >> this produces SQL that obeys the same form I see at >>> >> >> >> >>> https://www.postgresql.org/docs/current/static/queries-with.html. >>> >> >> >> >>> >> >> >> Since P2B.ancestors produces a new selectable each time, you >>> need to >>> >> >> >> assign it to a variable in order to refer to its set of columns >>> >> >> >> without re-introducing it. >>> >> >> >> >>> >> >> >> >>> >> >> >> >>> >> >> >> >>> >> >> >> > >>> >> >> >> > >>> >> >> >> > On Thursday, June 7, 2018 at 7:01:21 PM UTC-5, HP3 wrote: >>> >> >> >> >> >>> >> >> >> >> Hello >>> >> >> >> >> >>> >> >> >> >> >>> >> >> >> >> Having difficulty with CTE and @hybrid_property.expression >>> on a >>> >> >> >> >> adjacency >>> >> >> >> >> list model. >>> >> >> >> >> >>> >> >> >> >> >>> >> >> >> >> class P2B(Base): >>> >> >> >> >> __tablename__ = 'p2bases' >>> >> >> >> >> id = Column(Integer, primary_key=True) >>> >> >> >> >> classname = Column(String) >>> >> >> >> >> parent_id = Column( >>> >> >> >> >> Integer, >>> >> >> >> >> ForeignKey('p2bases.id', ondelete='CASCADE'), >>> >> >> >> >> index=True >>> >> >> >> >> ) >>> >> >> >> >> >>> >> >> >> >> parent = relationship( >>> >> >> >> >> 'P2B', >>> >> >> >> >> primaryjoin='P2B.parent_id == P2B.id', >>> >> >> >> >> foreign_keys='P2B.id', >>> >> >> >> >> uselist=False >>> >> >> >> >> ) >>> >> >> >> >> >>> >> >> >> >> __mapper_args__ = { >>> >> >> >> >> 'polymorphic_identity': 'P2B', >>> >> >> >> >> 'polymorphic_on': classname >>> >> >> >> >> } >>> >> >> >> >> >>> >> >> >> >> @hybrid_property >>> >> >> >> >> def ancestors(self): >>> >> >> >> >> _ancestors = [] >>> >> >> >> >> parent = self.parent >>> >> >> >> >> while parent is not None: >>> >> >> >> >> _ancestors.append(parent) >>> >> >> >> >> parent = parent.parent >>> >> >> >> >> return _ancestors >>> >> >> >> >> >>> >> >> >> >> @ancestors.expression >>> >> >> >> >> def ancestors(cls): >>> >> >> >> >> cte = select([P2B.id, P2B.parent_id]) \ >>> >> >> >> >> .where(P2B.id == cls.id) \ # <<<<<< Based on >>> >> >> >> >> Example1 >>> >> >> >> >> .cte(name='cte', recursive=True) >>> >> >> >> >> >>> >> >> >> >> cte = cte.union( >>> >> >> >> >> select([P2B.id, P2B.parent_id]) >>> >> >> >> >> .where(P2B.id == cte.c.parent_id) >>> >> >> >> >> >>> >> >> >> >> ) >>> >> >> >> >> return cte >>> >> >> >> >> >>> >> >> >> >> >>> >> >> >> >> >>> >> >> >> >> >>> >> >> >> >> >>> >> >> >> >> >>> >> >> >> >> The issue I am facing is that the SQL statement for >>> ancestors >>> >> >> >> >> expression >>> >> >> >> >> becomes this >>> >> >> >> >> >>> >> >> >> >> >>> >> >> >> >> >>> >> >> >> >> >>> >> >> >> >> WITH RECURSIVE cte(id, parent_id) AS >>> >> >> >> >> >>> >> >> >> >> (SELECT p2bases.id AS id, p2bases.parent_id AS parent_id >>> >> >> >> >> >>> >> >> >> >> FROM p2bases >>> >> >> >> >> >>> >> >> >> >> WHERE p2bases.id = <a href="http://p2bases.id"; >>> target="_blank" rel="nofollow" onmousedown="this.href=' >>> http://www.google.com/url?q\x3dhttp%3A%2F%2Fp2bases.id\x26sa\x3dD\x26sntz\x3d1\x26usg\x3dAFQjCNFXb6853cCgweqpw68fbajiKFHNJg';return >>> <http://www.google.com/url?q%5Cx3dhttp%3A%2F%2Fp2bases.id%5Cx26sa%5Cx3dD%5Cx26sntz%5Cx3d1%5Cx26usg%5Cx3dAFQjCNFXb6853cCgweqpw68fbajiKFHNJg';return> >>> true;" onclick="this.href=' >>> http://www.google.com/url?q\x3dhttp%3A%2F%2Fp2bases.id\x26sa\x3dD\x26sntz\x3d1\x26usg\x3dAFQj >>> <http://www.google.com/url?q%5Cx3dhttp%3A%2F%2Fp2bases.id%5Cx26sa%5Cx3dD%5Cx26sntz%5Cx3d1%5Cx26usg%5Cx3dAFQj> >> >> -- > SQLAlchemy - > The Python SQL Toolkit and Object Relational Mapper > > http://www.sqlalchemy.org/ > > To post example code, please provide an MCVE: Minimal, Complete, and > Verifiable Example. 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