Fastest way to insert object if it doesn't exist with SQLAlchemy

Question

So I\'m quite new to SQLAlchemy.

I have a model Showing which has about 10,000 rows in the table. Here is the class:

class Showing(Base):
    __tab         


        

Answer 1

If any such object is unique based on a combination of columns, you need to mark these as a composite primary key. Add the primary_key=True keyword parameter to each of these columns, dropping your id column altogether:

class Showing(Base):
    __tablename__   = "showings"

    time            = Column(DateTime, primary_key=True)
    link            = Column(String)
    film_id         = Column(Integer, ForeignKey('films.id'), primary_key=True)
    cinema_id       = Column(Integer, ForeignKey('cinemas.id'), primary_key=True)

That way your database can handle these rows more efficiently (no need for an incrementing column), and SQLAlchemy now automatically knows if two instances of Showing are the same thing.

I believe you can then just merge your new Showing back into the session:

def AddShowings(self, showing_times, cinema, film):
    for showing_time in showing_times:
        self.session.merge(
            Showing(time=showing_time[0], link=showing_time[1],
                    film=film, cinema=cinema)
        )