How to use query time calculations in model?

[20-buck-spin]

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Example Code

import sqlmodel
import sqlalchemy.sql.functions as sql_funcs

class StoreItem(sqlmodel.SQLModel, table=True)
    id: int | None = sqlmodel.Field(primary_key=True)
    price_a: int
    price_b: int 
    min_price: ???

Description

As the title suggests, I am trying to implement query time computed values for a model (the real example is complex with subqueries, etc. so i am presenting a simplified example)

Given the StoreItem class above, how can I create a query that does something like

select(StoreItem).options(with_expression(StoreItem.min_price, sql_func.func.least(StoreItem.price_a, StoreItem.price_b))

I found the SqlAlchemy docs in query_expression() and with_expression(). But when trying to use them, I get the error 'asyncpg.exceptions.UndefinedColumnError' because the query_expression column does not exist in the database.

I am assuming I may need to somehow approach this problem differently in the context of SqlModel. Any help would be much appreciated.

Operating System

Linux

Operating System Details

No response

SQLModel Version

0.0.21

Python Version

3.12

Additional Context

No response

[20-buck-spin]

So after a huge bunch of testing, this works only if the column does indeed exist in the table (I created a column that will always be null)

from sqlalchemy.orm import query_expression, with_expression
import sqlalchemy.sql.functions as sql_funcs


class StoreItem(sqlmodel.SQLModel, table=True)
    id: int | None = sqlmodel.Field(primary_key=True)
    price_a: int
    price_b: int 
    min_price: int | None = query_expression()


# Query
stmt = select(StoreItem).options(with_expression(StoreItem.min_price, sql_funcs.func.least(StoreItem.price_a, StoreItem.price_b)))

As I understand, this isn't the desired behaviour? Should I create an issue on it? I could try looking for a solution if someone can give me hints on where to start.