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1. hitman-gdg

   added

   featureNew feature or requestNew feature or request

   on Sep 14, 2021
2. hitman-gdg

   changed the title [-]Add support for diferred column loading[/-] [+]Add support for deferred column loading[/+] on Sep 14, 2021
3. eddcorts commented on Mar 25, 2022

   

   eddcorts

   on Mar 25, 2022

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   Having same issue, did you find any alternative with base SQLAlchemy or something?
4. FilipeMarch commented on May 13, 2023

   

   FilipeMarch

   on May 13, 2023

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   Did you find a solution?
5. lucas-labs commented on Nov 9, 2023

   

   lucas-labs

   on Nov 9, 2023

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   I think that we can use the new sa_type now, in order to achieve this behaviour.
6. ngi commented on Mar 28, 2024

   

   ngi

   on Mar 28, 2024

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   any news how to use sa_type for deferred loading?
7. MarkusDressel commented on Nov 14, 2024

   

   MarkusDressel

   on Nov 14, 2024

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   @tiangolo can you provide some information if / how it possible to leverage SQLalchemy's deferred loading mechanism in SQLModel ?

   I also could not find a way to make deferred loading on column level (not on query level) work. sa_column setting is not recognized by SQLModel and still loads the deferred column

   blob: bytes | None = Field(default=None, sa_column=deferred(Column(LargeBinary)))

   Reacted by chentt, Vinicius Abade, Kalel L. Martinho, matan-prime, Fatem From DailyDoses, Ridwan Mulyadi and Lars Alexander Blumberg
8. Fatem-Mq commented on Feb 28, 2025

   

   Fatem-Mq

   on Feb 28, 2025

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   Any updates? =(
9. shawnmartin-py commented on Feb 28, 2025

   

   shawnmartin-py

   on Feb 28, 2025

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   Why anyone would even consider sqlmodel these days is beyond me.
   Been fine managing Pydantic and SQLA models independently for the past 3 years.
10. shawnmartin-py commented on Feb 28, 2025

    

    shawnmartin-py

    on Feb 28, 2025

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    It's a lib that get's hardly any updates, and only 1 person is allowed to merge PR's. 🤦‍♂️
11. alessiamarcolini commented on Jul 25, 2025

    

    alessiamarcolini

    on Jul 25, 2025

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    Hi! Is there an update on how to make this work? :) Thanks.
12. YuriiMotov commented on Aug 13, 2025

    

    YuriiMotov

    on Aug 13, 2025

    Member

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    It seems that for now there is no way to declare model with the deferred field, and we can only defer column loading by specifying the option for query:

    session.get(User, 1, options=[defer(User.data)])

    or

    u = session.exec(
        select(User).where(col(User.id) == 1).options(defer(User.data))
    ).one()

    Reacted by Ilia Burakov
13. justanotherbody commented on Jan 16, 2026

    

    justanotherbody

    on Jan 16, 2026

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    Came looking for support, found this issue, determined a workaround...

    from typing import List
    
    import sqlalchemy
    import sqlalchemy.orm
    
    import sqlmodel
    
    
    def defer_columns(*columns: List[str]):
        def defer_columns_for_sqlmodel_class(cls):
            mapper = sqlalchemy.inspect(cls)
            for column in columns:
                prop = mapper.get_property(column)
                prop.deferred = True
                new_strategy = []
                # we expect strategy_key to be a tuple of (name, value) pairs but we're
                # going to be extra careful here...
                for strategy in prop.strategy_key:
                    if (
                        isinstance(strategy, tuple)
                        and len(strategy) == 2
                        and isinstance(strategy[0], str)
                        and strategy[0] == "deferred"
                    ):
                        new_strategy.append(("deferred", True))
                    else:
                        new_strategy.append(strategy)
                prop.strategy_key = tuple(new_strategy)
    
            # normally invoked automatically, but you might need to do this explicitly if
            # you're up to really unusual things...
            # sqlalchemy.orm.configure_mappers()
    
            return cls
    
        return defer_columns_for_sqlmodel_class
    
    
    @defer_columns("deferred_by_default")
    class Foo(sqlmodel.SQLModel, table=True):
    
        id: int = sqlmodel.Field(primary_key=True)
        always_loaded: str
        deferred_by_default: str
    
    
    def get_attrs(model):
        "Return underling attributes."
        return model._sa_instance_state.dict
    
    
    # test_engine is a pytest fixture with a working test DB connection. YMMV
    def test_deferred(test_engine):
        session = sqlmodel.Session(test_engine)
    
        session.add(Foo(id=1, always_loaded="Happy", deferred_by_default="Sad"))
        session.commit()
        session.expire_all()
    
        select = sqlmodel.select(Foo).where(Foo.id == 1)
    
        explicitly_deferred = session.exec(
            select.options(sqlalchemy.orm.defer(Foo.deferred_by_default))
        ).one()
    
        assert "always_loaded" in get_attrs(explicitly_deferred)
        assert "deferred_by_default" not in get_attrs(explicitly_deferred)
        session.expire_all()
    
        explicitly_loaded = session.exec(
            select.options(sqlalchemy.orm.undefer(Foo.deferred_by_default))
        ).one()
        assert "deferred_by_default" in get_attrs(explicitly_loaded)
        session.expire_all()
    
        foo = session.exec(select).one()
        assert "deferred_by_default" not in get_attrs(foo)

    Reacted by Alessia Marcolini, Hank, Will Blaschko and UncleDrew92
14. natikos commented on Feb 13, 2026

    

    natikos

    on Feb 13, 2026

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    any updates on this issue?
15. fastapi

    locked and limited conversation to collaborators on May 18, 2026
16. tiangolo

    converted this issue into a discussion #1931 on May 18, 2026