✨ Add new method `sqlmodel_update()` to update models in place, including an `update` parameter for extra data by tiangolo · Pull Request #804 · fastapi/sqlmodel · GitHub
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# Update with Extra Data (Hashed Passwords) with FastAPI
In the previous chapter I explained to you how to update data in the database from input data coming from a **FastAPI** *path operation*.
Now I'll explain to you how to add **extra data**, additional to the input data, when updating or creating a model object.
This is particularly useful when you need to **generate some data** in your code that is **not coming from the client**, but you need to store it in the database. For example, to store a **hashed password**.
## Password Hashing
Let's imagine that each hero in our system also has a **password**.
We should never store the password in plain text in the database, we should only stored a **hashed version** of it.
"**Hashing**" means converting some content (a password in this case) into a sequence of bytes (just a string) that looks like gibberish.
Whenever you pass exactly the same content (exactly the same password) you get exactly the same gibberish.
But you **cannot convert** from the gibberish **back to the password**.
### Why use Password Hashing
If your database is stolen, the thief won't have your users' **plaintext passwords**, only the hashes.
So, the thief won't be able to try to use that password in another system (as many users use the same password everywhere, this would be dangerous).
/// tip
You could use <a href="https://passlib.readthedocs.io/en/stable/" class="external-link" target="_blank">passlib</a> to hash passwords.
In this example we will use a fake hashing function to focus on the data changes. 🤡
///
## Update Models with Extra Data
The `Hero` table model will now store a new field `hashed_password`.
And the data models for `HeroCreate` and `HeroUpdate` will also have a new field `password` that will contain the plain text password sent by clients.
In previous examples, we have used something like:
```Python
db_hero = Hero.model_validate(hero)
```
This creates a `Hero` (which is a *table model*) object from the `HeroCreate` (which is a *data model*) object that we received in the request.
And this is all good... but as `Hero` doesn't have a field `password`, it won't be extracted from the object `HeroCreate` that has it.
`Hero` actually has a `hashed_password`, but we are not providing it. We need a way to provide it...
### Dictionary Update
Let's pause for a second to check this, when working with dictionaries, there's a way to `update` a dictionary with extra data from another dictionary, something like this:
```Python hl_lines="14"
db_user_dict = {
"name": "Deadpond",
"secret_name": "Dive Wilson",
"age": None,
}
hashed_password = "fakehashedpassword"
extra_data = {
"hashed_password": hashed_password,
"age": 32,
}
db_user_dict.update(extra_data)
print(db_user_dict)
# {
# "name": "Deadpond",
# "secret_name": "Dive Wilson",
# "age": 32,
# "hashed_password": "fakehashedpassword",
# }
```
This `update` method allows us to add and override things in the original dictionary with the data from another dictionary.
So now, `db_user_dict` has the updated `age` field with `32` instead of `None` and more importantly, **it has the new `hashed_password` field**.
### Create a Model Object with Extra Data
Similar to how dictionaries have an `update` method, **SQLModel** models have a parameter `update` in `Hero.model_validate()` that takes a dictionary with extra data, or data that should take precedence:
Now, `db_hero` (which is a *table model* `Hero`) will extract its values from `hero` (which is a *data model* `HeroCreate`), and then it will **`update`** its values with the extra data from the dictionary `extra_data`.
It will only take the fields defined in `Hero`, so **it will not take the `password`** from `HeroCreate`. And it will also **take its values** from the **dictionary passed to the `update`** parameter, in this case, the `hashed_password`.
If there's a field in both `hero` and the `extra_data`, **the value from the `extra_data` passed to `update` will take precedence**.
## Update with Extra Data
Now let's say we want to **update a hero** that already exists in the database.
The same way as before, to avoid removing existing data, we will use `exclude_unset=True` when calling `hero.model_dump()`, to get a dictionary with only the data sent by the client.
The method `db_hero.sqlmodel_update()` was added in SQLModel 0.0.16. 😎
///
## Recap
You can use the `update` parameter in `Hero.model_validate()` to provide extra data when creating a new object and `Hero.sqlmodel_update()` to provide extra data when updating an existing object. 🤓
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@@ -154,12 +154,13 @@ Then we use that to get the data that was actually sent by the client:
/// tip
Before SQLModel 0.0.14, the method was called `hero.dict(exclude_unset=True)`, but it was renamed to `hero.model_dump(exclude_unset=True)` to be consistent with Pydantic v2.
///
## Update the Hero in the Database
Now that we have a **dictionary with the data sent by the client**, we can iterate for each one of the keys and the values, and then we set them in the database hero model `db_hero` using `setattr()`.
Now that we have a **dictionary with the data sent by the client**, we can use the method `db_hero.sqlmodel_update()` to update the object `db_hero`.
@@ -175,19 +176,17 @@ Now that we have a **dictionary with the data sent by the client**, we can itera
///
If you are not familiar with that `setattr()`, it takes an object, like the `db_hero`, then an attribute name (`key`), that in our case could be `"name"`, and a value (`value`). And then it **sets the attribute with that name to the value**.
/// tip
So, if `key` was `"name"` and `value` was `"Deadpuddle"`, then this code:
The method `db_hero.sqlmodel_update()` was added in SQLModel 0.0.16. 🤓
```Python
setattr(db_hero, key, value)
```
Before that, you would need to manually get the values and set them using `setattr()`.
...would be more or less equivalent to:
///
```Python
db_hero.name = "Deadpuddle"
```
The method `db_hero.sqlmodel_update()` takes an argument with another model object or a dictionary.
For each of the fields in the **original** model object (`db_hero` in this example), it checks if the field is available in the **argument** (`hero_data` in this example) and then updates it with the provided value.
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✨ Add new method sqlmodel_update() to update models in place, including an update parameter for extra data #804
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✨ Add new method sqlmodel_update() to update models in place, including an update parameter for extra data #804
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