* Decompressing gzip-compressed request bodies.
* Automatically logging all request bodies.

## Handling custom request body encodings

Let's see how to make use of a custom `Request` subclass to decompress gzip requests.

And an `APIRoute` subclass to use that custom request class.

### Create a custom `GzipRequest` class

!!! tip

!!! note "Technical Details"
    Actually, `Query`, `Path` and others you'll see next create objects of subclasses of a common `Param` class, which is itself a subclass of Pydantic's `FieldInfo` class.

    And Pydantic's `Field` returns an instance of `FieldInfo` as well.

    `Body` also returns objects of a subclass of `FieldInfo` directly. And there are others you will see later that are subclasses of the `Body` class.

This simple case is handled automatically by FastAPI because the return type annotation is the class (or a subclass) of `Response`.

And tools will also be happy because both `RedirectResponse` and `JSONResponse` are subclasses of `Response`, so the type annotation is correct.

### Annotate a Response Subclass

You can also use a subclass of `Response` in the type annotation:

```Python hl_lines="8-9"

### `UserInDB` model

Now, let's create a `UserInDB` model.

This will have the data that is actually stored in the database.

We don't create it as a subclass of Pydantic's `BaseModel` but as a subclass of our own `User`, because it will have all the attributes in `User` plus a couple more:

```Python hl_lines="31-33"
{!../../../docs_src/nosql_databases/tutorial001.py!}
```

!!! note

 * The performance of these calls on the underlying network. If the network’s performance isn’t sufficient, you need to either improve the network or use less of it.

### EventListener

avoids/fixes a potential security issue: as the returned object is passed directly to Pydantic, if the returned object was a subclass of the `response_model` (e.g. you return a `UserInDB` that inherits from `User` but contains extra fields, like `hashed_password`, and `User` is used in the `response_model`), it would still pass the validation (because `UserInDB` is a subclass of `User`) and the object would be returned as-is, including the `hashed_password`. To fix this, the declared `response_model`...

        }

        return overriddenDescriptors
    }

    override fun isSubClassOf(subClass: KtClassOrObjectSymbol, superClass: KtClassOrObjectSymbol): Boolean {
        if (subClass == superClass) return false

        val subClassDescriptor = getSymbolDescriptor(subClass) as? ClassDescriptor ?: return false
        val superClassDescriptor = getSymbolDescriptor(superClass) as? ClassDescriptor ?: return false

) : KtSubstitutorProvider(), KtFirAnalysisSessionComponent {
    override fun createSubstitutor(
        subClass: KtClassOrObjectSymbol,
        superClass: KtClassOrObjectSymbol,
    ): KtSubstitutor? {
        if (subClass == superClass) return KtSubstitutor.Empty(token)

        val baseFirSymbol = subClass.firSymbol
        val superFirSymbol = superClass.firSymbol

             * no separate symbol for that case.
             *
             * Java statics present a similar case - they can be imported not only from the declaring class,
             * but also from any subclass.
             */
            private fun FirQualifiedAccessExpression.importableNameForImplicitlyDispatchedCallable(): FqName? {
                val dispatchReceiver = dispatchReceiver
                if (

        require(subClass is KtFirSymbol<*>)
        require(superClass is KtFirSymbol<*>)

        if (subClass == superClass) return false
        return isSubClassOf(
            subClass = subClass.firSymbol.fir as FirClass,
            superClass = superClass.firSymbol.fir as FirClass,
            rootModuleSession,