SQLAlchemy join onto an inline table - python-3.x

Question

I have an inline defined table:
select(
Values(column('key', String), column('value', String), column('ordering', Integer), name='subq')
.data([(e.name, e.value, i) for i, e in enumerate(DurationType)])
This produces this SQL:
select key, value, ordering
from (values ("key1", "name1", 1), ("key2", "name2", 2) ...)
Which is a fine table:
Now i need to join this subquery to another one. The other query is:
self.session.query(self.model)
.filter(self.model.duration != None)
.with_entities(
duration_bucket := case((self.model.duration < 60, DurationType.LESS_THAN_1.name),
(and_(60 <= self.model.duration, self.model.duration < 60 * 5),
DurationType.FROM_1_TO_5.name),
(and_(60 * 5 <= self.model.duration,
self.model.duration < 60 * 10), DurationType.FROM_5_TO_10.name),
(and_(60 * 10 <= self.model.duration,
self.model.duration < 60 * 20), DurationType.FROM_10_TO_20.name),
(and_(60 * 20 <= self.model.duration,
self.model.duration < 60 * 30), DurationType.FROM_20_TO_30.name),
(60 * 30 <= self.model.duration, DurationType.MORE_THAN_30.name)
).label('id'))
.group_by(duration_bucket)
.having(count() > 0)
Which is apart from case clause is just a select from aggregation, that leaves me with a result of single column "id"
But for the life of me I can't figure how to join it. My initial attempt looked like this:
inline_enum_table = select(
Values(column('key', String), column('value', String), column('ordering', Integer), name="suqb")
.data([(e.name, e.value, i) for i, e in enumerate(DurationType)])).subquery()
inline_enum_table = self.session.query(inline_enum_table)
return (
self.session.query(self.model)
.filter(self.model.duration != None)
.with_entities(
duration_bucket := case((self.model.duration < 60, DurationType.LESS_THAN_1.name),
(and_(60 <= self.model.duration, self.model.duration < 60 * 5),
DurationType.FROM_1_TO_5.name),
(and_(60 * 5 <= self.model.duration,
self.model.duration < 60 * 10), DurationType.FROM_5_TO_10.name),
(and_(60 * 10 <= self.model.duration,
self.model.duration < 60 * 20), DurationType.FROM_10_TO_20.name),
(and_(60 * 20 <= self.model.duration,
self.model.duration < 60 * 30), DurationType.FROM_20_TO_30.name),
(60 * 30 <= self.model.duration, DurationType.MORE_THAN_30.name)
).label('id'))
.group_by(duration_bucket)
.having(count() > 0)
.join(duration_enum := inline_enum_table.label('qwe'), duration_enum.key == duration_bucket)
This particular attempt results in sqlalchemy.exc.ArgumentError: Expected mapped entity or selectable/table as join target
I've had many more tries with all sorts of errors.

Answer 1

I got the following to work. select().subquery() is what helps SQLAlchemy work with such objects as part of a FROM clause.
from sqlalchemy import Column, column, create_engine, Integer, join, select, String, values
from sqlalchemy.orm import declarative_base, Session
engine = create_engine("postgresql://scott:tiger#192.168.0.199/test")
Base = declarative_base()
class Thing(Base):
__tablename__ = "thing"
id = Column(Integer, primary_key=True, autoincrement=False)
key = Column(String(50))
def __repr__(self):
return f"Thing(id={repr(self.id)}, key={repr(self.key)})"
Base.metadata.drop_all(engine)
Base.metadata.create_all(engine)
with Session(engine) as sess, sess.begin():
sess.add_all(
[
Thing(id=1, key="key1"),
Thing(id=2, key="key2"),
]
)
inline_enum_table = select(
values(
column("key", String),
column("value", String),
column("ordering", Integer),
name="inline_enums",
literal_binds=True,
).data(
[
("key1", "name1", 1),
("key2", "name2", 2),
]
)
).subquery()
with Session(engine) as sess:
query = select(Thing, inline_enum_table.c.value).select_from(
join(Thing, inline_enum_table, Thing.key == inline_enum_table.c.key)
)
print(query)
"""
SELECT thing.id, thing.key, anon_1.value
FROM thing JOIN (SELECT inline_enums.key AS key, inline_enums.value AS value, inline_enums.ordering AS ordering
FROM (VALUES ('key1', 'name1', 1), ('key2', 'name2', 2)) AS inline_enums (key, value, ordering)) AS anon_1 ON thing.key = anon_1.key
"""
results = sess.execute(query).all()
print(results)
# [(Thing(id=1, key='key1'), 'name1'), (Thing(id=2, key='key2'), 'name2')]