Optional: Local caching

To guarantee quick and continuous access for customers, Amplify DataStore employs a local cached version of remote data. During your transition from Amplify DataStore, you should choose a local storage solution that aligns with your models to avoid unnecessary complexity.

See the helpful resources page for third-party package suggestions.

Local models

You will need to create a separate model for local storage that corresponds to your Amplify GraphQL generated model. To exclusively use your Amplify models, you must develop functions for mapping between your Amplify and local models, ensuring the local model remains concealed from the rest of your implementation.

static LocalModel _toLocalModel(RemoteModel remote) {
  return LocalModel(
    id: remote.id,
    someString: remote.someString,
    createdAt: remote.createdAt?.getDateTimeInUtc(),
    updatedAt: remote.updatedAt?.getDateTimeInUtc(),
  );
}

static RemoteModel _toRemoteModel(LocalModel local) {
  return RemoteModel(
    id: local.id,
    someString: local.someString,
  );
}

Certain database libraries lack or offer limited support for custom primary keys. You have the option to use the libraries' limited primary keys alongside your model's primary keys, but it is advisable to choose a database that accommodates the structure of your models. When changing your schema version, DataStore will discard your data to prevent any model incompatibilities.

CRUD

The standard practice in local store operations involves the implementation of interfaces for creating, reading, updating, and deleting. However, it is crucial to consider the relationships between your models. In SQL, when handling 1:1 or 1:many relationships with models, it becomes necessary to create multiple tables and corresponding joins for CRUD operations. When dealing with NoSQL, a basic query for models with a many-to-many relationship may require the use of multiple sub-queries to link the relational data.

Queries

Amplify DataStore uses query predicates, pagination, and sort by parameters to generate queries for Amplify API and its local store solution. Storing all data locally simplifies implementation by only requiring handling of local store queries. Otherwise, you have to generate matching queries for Amplify API and your local store.

Observability

To support a responsive app, pick a local store that supports observing data changes. Alternatively, you can create your own observe Stream that you trigger after every create, update, or delete.

Stream<void> observe() {
  return localRepository.observe();
}