CODEWITHSUNDEEP
pythonpostgresqlviewormsqlalchemy
Urban48
Urban48

Reputation: 1476

sqlalchemy creating VIEW with ORM

I created the following ORM:

from sqlalchemy import Column, Integer, String, UniqueConstraint
from sqlalchemy.dialects.postgresql import JSONB
from sqlalchemy.ext.declarative import declarative_base
Base = declarative_base()


class TableA(Base):
    __tablename__ = 'table_a'

    id = Column(Integer, primary_key=True, nullable=False)
    identifier = Column(String(320))
    internal_id = Column(Integer)
    type = Column(String(32))
    time = Column(DateTime(timezone=True))
    success = Column(Boolean())
    parameters = Column(JSONB())



class TableB(Base):
    __tablename__ = 'table_b'
    __table_args__ = (UniqueConstraint('generate_action',
                                       'print_action',
                                        name='my_action_key'),)

    id = Column(Integer, primary_key=True, autoincrement=True, nullable=False)
    generate_action = Column(Integer)
    print_action = Column(Integer)
    generate_action = Column(Integer)
    coupon_code = Column(String(300))
    number_of_rebought_items = Column(Integer)
    seconds_between_rebuy = Column(Integer)

I'm trying to figure out how to convert the following raw SQL view to ORM syntax with sqlalchemy.

CREATE VIEW my_view AS
    SELECT table_b.id as table_b_id,
        tb.coupon_code as coupon_code,
        tb.number_of_rebought_items as number_of_rebought_items,
        ta.id as table_a_action_id,
        ta.time as time,
        ta.parameters as parameters,
    FROM table_b tb
    LEFT JOIN table_a ta on
        ta.id = tb.generate_action;

Couldn't find any good examples out there of how to do it with ORM.
So far, my solution is to just run raw sql to create this view.

can anyone point me to the right direction, or give an example of how to create views with sqlalchemy orm?

Is it possible to create the views with metadata.create_all()

Upvotes: 22

Views: 18303

Answers (1)

Haleemur Ali
Haleemur Ali

Reputation: 28243

the library sqlalchemy-utils now includes functionality for creating views, and it associates the view with sqlalchemy's metadata so that it is possible to create the view using Base.metadata.create_all

example:

# installation: pip install sqlalchemy-utils
from sqlalchemy_utils import create_view
from sqlalchemy import select, func

# engine Base & Table declaration elided for brevity

stmt = select([
    TableB.id.label('table_b_id'),
    TableB.coupon_code,
    TableB.number_of_rebought_items,
    TableA.id.label('table_a_action_id'),
    TableA.time,
    TableA.parameters
]).select_from(TableB.__table__.outerjoin(TableA, TableB.generate_action == TableA.id))

# attaches the view to the metadata using the select statement
view = create_view('my_view', stmt, Base.metadata)

# provides an ORM interface to the view
class MyView(Base):
    __table__ = view

# will create all tables & views defined with ``create_view``
Base.metadata.create_all()

# At this point running the following yields 0, as expected,
# indicating that the view has been constructed on the server 
engine.execute(select([func.count('*')], from_obj=MyView)).scalar()

Upvotes: 16

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