I'm sorry if I'm being dense here then:
In my game class - do I just do something like this?
class Game(Base):
id = Column('id') # UUID PRIMARY KEY, etc.....
# Stuff
def _get_leaderboard(self, SessionObj):
SessionObj.query(.....# blah blah blah
leaderboard = _get_leaderboard
Or what am I missing here?
I wouldn't flood the thread if I knew what to google to flesh this out,
sorry. I've seen thousands of examples and nothing seems to match up with
what I want to do.
On Thu, May 23, 2019 at 12:07 PM Simon King <[email protected]> wrote:
> On Thu, May 23, 2019 at 10:47 AM Michael P. McDonnell
> <[email protected]> wrote:
> >
> > So if I understand what I'm reading correctly: if I do the
> object-session, I can do the query - but I can only get 1 "column"'s worth
> of information or SA tends to be unhappy with the result.
>
> I don't know what you mean by this. Once you've got the session, you
> can perform any query you like and return whatever information you
> like, including multiple columns and multiple rows.
>
> >
> > That kind of actually puts me on the second link - which then if I am to
> understand correctly: I create a "select" which is then the "_table_" for
> the Leaderboard class?
> > How would I "pass in" the game id to match against? (I don't need a
> group_by for game if there's only 1 game)
> >
> > Effectively - my game class should eventually look like this?
> >
> > class Game(Base):
> > id = Column('id') # UUID PRIMARY KEY, etc.....
> > # Stuff
> > leaderboard = relationship("Leaderboard")
> >
> > and my Leaderboard class like this:
> > lb_select = select( Person.display_name, func.count(Result.task_id),
> func.sum(Result.finish_dttm - Result.start_dttm -
> Result.validation_time).join(Play).join(Person).join(Game).where(Game.id ==
> #PASSED IN ID).group_by(Person.display_name)
> >
> > class Leaderboard(Base):
> > _table_ = lb_select
> >
> > Is this remotely correct? Or am I missing something really obvious?
> >
>
> To go down this road, you would write your query so that it returns
> the leaderboard for *all* games. You wouldn't filter on Game.id at
> all. When you make the relationship between Game and Leaderboard,
> SQLAlchemy will join the Game table to the Leaderboard as a subquery
> and add the game ID as the join criterion. I don't know if your
> database's query planner will be intelligent enough to realise that
> the game ID restriction can be pushed down into the subquery as well.
> If it *is*, the performance should be pretty good. If it *isn't*,
> performance will degrade as the number of plays increases.
>
> Simon
>
> --
> SQLAlchemy -
> The Python SQL Toolkit and Object Relational Mapper
>
> http://www.sqlalchemy.org/
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