Posts tagged: sqlmodel

💭 Proper handling of None in WHERE condition · Issue #109 · fast...

2024-11-08T13:36:30Z

Proper handling of None in WHERE condition · Issue #109 · fastapi/sqlmodel

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...

GitHub · github.com

SQLModel models ship with an is_, and is_not that you can use to compare to None without pesky linters complaining.

This comment summed it up quite well.

I believe this is concerned entirely with SQLAlchemy, not with SQLModel, and has to do with the required semantics to construct a BinaryExpression object. Hero.age == None evaluates to a BinaryExpression object which is eventually used to construct the SQL query that the SQLAlchemy engine issues to your DBMS. Hero.age is None evaluates to False immediately, and not a BinaryExpression, which short-circuits the query no matter the value of age in a row. From a cursory search, it does not seem that the is operator can be overridden in Python. This could help explain why the only possibility is by using the == operator, which can be overridden.

so rather than using Team.heros == None we can use Team.seros.is_(None) which checks for itentity not equality.

Note

This post is a thought. It’s a short note that I make about someone else’s content online #thoughts

💭 Read a Range of Data - LIMIT and OFFSET - SQLModel

2024-01-12T02:18:35Z

Read a Range of Data - LIMIT and OFFSET - SQLModel

SQLModel, SQL databases in Python, designed for simplicity, compatibility, and robustness.

sqlmodel.tiangolo.com

Today I was running some sqlmodel queries through the sqlalchemy orm. Admittedly I’ve not done enough orm queries before, and I’ve done quite a bit of raw sql. I was trying to get objects from two separate models that had relationships setup.

session.query(User, Images).where(User.id == 3).all()

It is incredibly slow, and gives me the following warning.

SELECT statement has a cartesian product between FROM element(s)

What I learned from the SQLModel docs is that you should give it a join to correct this and go much faster.

session.query(User, Images).join(Images).where(User.id == 3).all()

Note

This post is a thought. It’s a short note that I make about someone else’s content online #thoughts

💭 Filter Data - WHERE - SQLModel

2023-07-28T14:59:37Z

Filter Data - WHERE - SQLModel

SQLModel, SQL databases in Python, designed for simplicity, compatibility, and robustness.

sqlmodel.tiangolo.com

When fetching pydantic models from the database with sqlmodel, and you cannot select your item by id, you probably need to use a where clause. This is the sqlmodel way of doing it.

Here is a snippet of how I am using sqlmodel select and where to find a post by link in my thoughts database.

@post_router.get("/link/")
async def get_post_by_link(
    *,
    session: Session = Depends(get_session),
    link: str,
) -> PostRead:
    "get one post by link"
    link = urllib.parse.unquote(link)
    print(f'link: {link}')
    post = session.exec(select(Post).where(Post.link==link)).first()
    if not post:
        raise HTTPException(status_code=404, detail=f"Post not found for link: {link}")

    return post

Note

This post is a thought. It’s a short note that I make about someone else’s content online #thoughts