Snapshots | laravel-event-sourcing | Spatie

 SPATIE

  Laravel Event Sourcing
=========================

spatie.be/open-source

  [Docs](https://spatie.be/docs)  [Laravel-event-sourcing](https://spatie.be/docs/laravel-event-sourcing/v6)  Using-aggregates  Snapshots

 Version   v7   v6   v5   v4   v3   v2   v1

 Other versions for crawler [v7](https://spatie.be/docs/laravel-event-sourcing/v7) [v6](https://spatie.be/docs/laravel-event-sourcing/v6) [v5](https://spatie.be/docs/laravel-event-sourcing/v5) [v4](https://spatie.be/docs/laravel-event-sourcing/v4) [v3](https://spatie.be/docs/laravel-event-sourcing/v3) [v2](https://spatie.be/docs/laravel-event-sourcing/v2) [v1](https://spatie.be/docs/laravel-event-sourcing/v1)

- [ Introduction ](https://spatie.be/docs/laravel-event-sourcing/v6/introduction)
- [ Support us ](https://spatie.be/docs/laravel-event-sourcing/v6/support-us)
- [ Requirements ](https://spatie.be/docs/laravel-event-sourcing/v6/requirements)
- [ Installation & setup ](https://spatie.be/docs/laravel-event-sourcing/v6/installation-setup)
- [ Questions and issues ](https://spatie.be/docs/laravel-event-sourcing/v6/questions-issues)
- [ Changelog ](https://spatie.be/docs/laravel-event-sourcing/v6/changelog)
- [ Upgrading ](https://spatie.be/docs/laravel-event-sourcing/v6/upgrading)
- [ Resources and alternatives ](https://spatie.be/docs/laravel-event-sourcing/v6/resources-and-alternatives)
- [ About us ](https://spatie.be/docs/laravel-event-sourcing/v6/about-us)

Getting familiar with event sourcing
------------------------------------

- [ Introduction ](https://spatie.be/docs/laravel-event-sourcing/v6/getting-familiar-with-event-sourcing/introduction)
- [ The traditional application ](https://spatie.be/docs/laravel-event-sourcing/v6/getting-familiar-with-event-sourcing/the-traditional-application)
- [ Using projectors to transform events ](https://spatie.be/docs/laravel-event-sourcing/v6/getting-familiar-with-event-sourcing/using-projectors-to-transform-events)
- [ Using aggregates to make decisions based on the past ](https://spatie.be/docs/laravel-event-sourcing/v6/getting-familiar-with-event-sourcing/using-aggregates-to-make-decisions-based-on-the-past)

Using projectors
----------------

- [ Writing your first projector ](https://spatie.be/docs/laravel-event-sourcing/v6/using-projectors/writing-your-first-projector)
- [ Creating and registering projectors ](https://spatie.be/docs/laravel-event-sourcing/v6/using-projectors/creating-and-configuring-projectors)
- [ Making sure events get handled in the right order ](https://spatie.be/docs/laravel-event-sourcing/v6/using-projectors/making-sure-events-get-handled-in-the-right-order)
- [ Thinking in events ](https://spatie.be/docs/laravel-event-sourcing/v6/using-projectors/thinking-in-events)

Using reactors
--------------

- [ Writing your first reactor ](https://spatie.be/docs/laravel-event-sourcing/v6/using-reactors/writing-your-first-reactor)
- [ Creating and configuring reactors ](https://spatie.be/docs/laravel-event-sourcing/v6/using-reactors/creating-and-configuring-reactors)

Using aggregates
----------------

- [ Writing your first aggregate ](https://spatie.be/docs/laravel-event-sourcing/v6/using-aggregates/writing-your-first-aggregate)
- [ Creating and configuring aggregates ](https://spatie.be/docs/laravel-event-sourcing/v6/using-aggregates/creating-and-configuring-aggregates)
- [ Testing aggregates ](https://spatie.be/docs/laravel-event-sourcing/v6/using-aggregates/testing-aggregates)
- [ Snapshots ](https://spatie.be/docs/laravel-event-sourcing/v6/using-aggregates/snapshots)

Advanced usage
--------------

- [ Preparing events ](https://spatie.be/docs/laravel-event-sourcing/v6/advanced-usage/preparing-events)
- [ Replaying events ](https://spatie.be/docs/laravel-event-sourcing/v6/advanced-usage/replaying-events)
- [ Storing metadata ](https://spatie.be/docs/laravel-event-sourcing/v6/advanced-usage/storing-metadata)
- [ Handling exceptions ](https://spatie.be/docs/laravel-event-sourcing/v6/advanced-usage/handling-exceptions)
- [ Discovering projectors and reactors ](https://spatie.be/docs/laravel-event-sourcing/v6/advanced-usage/discovering-projectors-and-reactors)
- [ Using your own event storage model ](https://spatie.be/docs/laravel-event-sourcing/v6/advanced-usage/using-your-own-event-storage-model)
- [ Using your own event storage repository ](https://spatie.be/docs/laravel-event-sourcing/v6/advanced-usage/using-your-own-event-storage-repository)
- [ Using your own event serializer ](https://spatie.be/docs/laravel-event-sourcing/v6/advanced-usage/using-your-own-event-serializer)
- [ Using aliases for stored event classes ](https://spatie.be/docs/laravel-event-sourcing/v6/advanced-usage/using-aliases-for-stored-event-classes)
- [ Adding and Removing Projectors and Reactors ](https://spatie.be/docs/laravel-event-sourcing/v6/advanced-usage/adding-and-removing-projectors-and-reactors)
- [ Aggregate Partials ](https://spatie.be/docs/laravel-event-sourcing/v6/advanced-usage/aggregate-partials)
- [ Event Queries ](https://spatie.be/docs/laravel-event-sourcing/v6/advanced-usage/event-queries)
- [ Commands ](https://spatie.be/docs/laravel-event-sourcing/v6/advanced-usage/commands)

      You are viewing the documentation for **an older version** of this package. You can check the version you are using with the following command:

 `                                    composer show spatie/laravel-event-sourcing                                                                                                                                                                                                                                    `

Snapshots
=========

###  On this page

1. [ Creating a snapshot ](#content-creating-a-snapshot)
2. [ Customizing the stored snapshot state ](#content-customizing-the-stored-snapshot-state)
3. [ Want to know more? ](#content-want-to-know-more)

Snapshots are a way to reduce the amount of events you need to fetch and apply when instantiating your aggregate. When you have a large number of events per aggregate root, it might be something to consider to improve performance.

Creating a snapshot
-----------------------------------------------------------------------------------------------------------------

You can create a new snapshot by calling the `->snapshot()` method on your Aggregate.

```
$myAggregate = MyAggregate::retrieve($uuid);
$myAggregate->snapshot();
```

This will create a new snapshot in the `snapshots` table. By default we store the values of the public properties on the aggregate at that point in time.

When you retrieve the aggregate the next time, it will find the snapshot, set its internal properties back to what they were at the time of the snapshot, and apply any new events starting from the snapshot.

This uses the snapshots `aggregateVersion`, this version number is incremented each time an event is applied by the aggregate and stored in the snapshot.

Customizing the stored snapshot state
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------

If you want to customize the state that the snapshot stores of your aggregate, you can override the `getState()` and `useState()` methods on the aggregate.

### getState

The default implementation uses the Reflection api to get all properties and values of the aggregate and stores them as a serialized array in the database.

The only requirement here is that you return an array to be stored.

```
protected function getState(): array
{
    $class = new ReflectionClass($this);

    return collect($class->getProperties(ReflectionProperty::IS_PUBLIC))
        ->reject(fn (ReflectionProperty $reflectionProperty) => $reflectionProperty->isStatic())
        ->mapWithKeys(function (ReflectionProperty $property) {
            return [$property->getName() => $this->{$property->getName()}];
        })->toArray();
}
```

### useState

The default implementation gets every property from the array and sets them on the instance.

```
protected function useState(array $state): void
{
    foreach ($state as $key => $value) {
        $this->$key = $value;
    }
}
```

Want to know more?
------------------------------------------------------------------------------------------------------------

Aggregate roots are a crucial part in large applications. Our course, [Event Sourcing in Laravel](https://event-sourcing-laravel.com/) covers them in depth:

- 9. Aggregate Roots
- 16. Event Versioning
- 17. Snapshotting