:( 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? 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 <javascript:>> > 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 = p2bases.id UNION SELECT p2bases.id AS id, > >> >> >> p2bases.parent_id AS parent_id > >> >> >> > >> >> >> FROM p2bases, cte > >> >> >> > >> >> >> WHERE p2bases.id = cte.parent_id) > >> >> >> > >> >> >> SELECT p2bases.id AS p2bases_id, p2bases.classname AS > >> >> >> p2bases_classname, > >> >> >> p2bases.position AS p2bases_position, p2bases.parent_id AS > >> >> >> p2bases_parent_id, > >> >> >> cte.id AS cte_id, cte.parent_id AS cte_parent_id > >> >> >> > >> >> >> FROM p2bases, cte > >> >> >> > >> >> >> WHERE p2bases.id = %(id_1)s > >> >> >> > >> >> >> {'id_1': 1} > >> >> >> > >> >> >> > >> >> >> > >> >> >> Notice that `P2B.id == cls.id` in the cte becomes `p2bases.id = > >> >> >> p2bases.id`. > >> >> >> > >> >> >> > >> >> >> What am I missing in my @hypbrid_property.expression declaration? > >> >> >> > >> >> >> > >> >> >> How do I use my ancestors @hybrid_property.expression using > >> >> >> session.query(...)? > >> >> >> > >> >> >> ancestors = session.query(P2B.ancestors).get(a_child_id) > >> >> >> > >> >> >> > >> >> >> Example1: > >> >> >> > >> >> >> > >> >> >> > http://docs.sqlalchemy.org/en/latest/orm/extensions/hybrid.html#correlated-subquery-relationship-hybrid > > >> >> > > >> >> > -- > >> >> > 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. See http://stackoverflow.com/help/mcve for a > full > >> >> > description. > >> >> > --- > >> >> > You received this message because you are subscribed to the Google > >> >> > Groups > >> >> > "sqlalchemy" group. > >> >> > To unsubscribe from this group and stop receiving emails from it, > >> >> > send > >> >> > an > >> >> > email to sqlalchemy+...@googlegroups.com. > >> >> > To post to this group, send email to sqlal...@googlegroups.com. > >> >> > Visit this group at https://groups.google.com/group/sqlalchemy. > >> >> > For more options, visit https://groups.google.com/d/optout. > >> > > >> > -- > >> > 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. See http://stackoverflow.com/help/mcve for a > full > >> > description. > >> > --- > >> > You received this message because you are subscribed to the Google > >> > Groups > >> > "sqlalchemy" group. > >> > To unsubscribe from this group and stop receiving emails from it, > send > >> > an > >> > email to sqlalchemy+...@googlegroups.com. > >> > To post to this group, send email to sqlal...@googlegroups.com. > >> > Visit this group at https://groups.google.com/group/sqlalchemy. > >> > For more options, visit https://groups.google.com/d/optout. > > > > -- > > 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. See http://stackoverflow.com/help/mcve for a full > > description. > > --- > > You received this message because you are subscribed to the Google > Groups > > "sqlalchemy" group. > > To unsubscribe from this group and stop receiving emails from it, send > an > > email to sqlalchemy+...@googlegroups.com <javascript:>. > > To post to this group, send email to sqlal...@googlegroups.com > <javascript:>. > > Visit this group at https://groups.google.com/group/sqlalchemy. > > For more options, visit https://groups.google.com/d/optout. > -- 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. See http://stackoverflow.com/help/mcve for a full description. --- You received this message because you are subscribed to the Google Groups "sqlalchemy" group. To unsubscribe from this group and stop receiving emails from it, send an email to sqlalchemy+unsubscr...@googlegroups.com. To post to this group, send email to sqlalchemy@googlegroups.com. Visit this group at https://groups.google.com/group/sqlalchemy. For more options, visit https://groups.google.com/d/optout.
