Add support for deferred column loading

[hitman-gdg]

First Check

• I added a very descriptive title to this issue.
• I used the GitHub search to find a similar issue and didn't find it.
• I searched the SQLModel documentation, with the integrated search.
• I already searched in Google "How to X in SQLModel" and didn't find any information.
• I already read and followed all the tutorial in the docs and didn't find an answer.
• I already checked if it is not related to SQLModel but to Pydantic.
• I already checked if it is not related to SQLModel but to SQLAlchemy.

Commit to Help

• I commit to help with one of those options 👆

Example Code

from sqlmodel import deferred

class User(sqlmodel, table=True):
    id: Optional[int] = Field(primary_key=True, default=None)
    name: str
    data: Optional[bytes] = Field(deferred=True)

Description

The ability to be able to included deferred sql columns

Wanted Solution

I would like to be able to work with sqlalchemy deferred columns, so that certain columns are not loaded by default as part of a model

Wanted Code

from sqlmodel import deferred

Alternatives

No response

Operating System

macOS

Operating System Details

No response

SQLModel Version

0.0.4

Python Version

3.9.6

Additional Context

No response

[eddcorts]

Having same issue, did you find any alternative with base SQLAlchemy or something?

[FilipeMarch]

Did you find a solution?

[lucas-labs]

I think that we can use the new sa_type now, in order to achieve this behaviour.

[ngi]

any news how to use sa_type for deferred loading?

[MarkusDressel]

@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)))