Partition-Based Sync - Java SDK

Open a Synced Realm While Online

To open a synced realm, call getInstanceAsync(), passing in a SyncConfiguration object. The following code demonstrates how to create a realm with specific sync settings created using a SyncConfiguration object:

SyncConfiguration config = new SyncConfiguration.Builder(app.currentUser(), PARTITION)
        .allowQueriesOnUiThread(true)
        .allowWritesOnUiThread(true)
        .build();
Realm.getInstanceAsync(config, new Realm.Callback() {
    @Override
    public void onSuccess(Realm realm) {
        Log.v(
                "EXAMPLE",
                "Successfully opened a realm with reads and writes allowed on the UI thread."
        );
    }
});

val config = SyncConfiguration.Builder(app.currentUser(), PARTITION)
    .allowQueriesOnUiThread(true)
    .allowWritesOnUiThread(true)
    .build()
Realm.getInstanceAsync(config, object : Realm.Callback() {
    override fun onSuccess(realm: Realm) {
        Log.v("EXAMPLE", "Successfully opened a realm with reads and writes allowed on the UI thread.")
    }
})

The code above shows how to open the realm asynchronously by using getInstanceAsync(). You can also open a realm synchronously by using getInstance(), which returns an open realm before synchronizing all data from the backend. However, this may lead to temporary data inconsistencies while the remote data is downloaded, and is generally not recommended. You can use the waitForInitialRemoteData() configuration option to force the SDK to fetch remote data before opening the realm to avoid these inconsistencies.

The partition value specifies which subset of your data to sync. This is typically a user ID, project ID, store ID, or some other category identifier in your app that has particular relevance to the current user.

Open a Synced Realm While Offline

You can open a synced realm when offline with the exact same syntax that you use to open a synced realm while online. Not all SDKs follow this pattern, so cross-platform developers should consult the documentation for each SDK to learn more.

Updating Client Code After Migration

The automatic migration from Partition-Based Sync to Flexible Sync does not require any changes to your client code. However, to support this functionality, Realm automatically handles the differences between the two Sync Modes by:

• Automatically creating Flexible Sync subscriptions for each object type where partitionKey == partitionValue.

• Injecting a partitionKey field into every object if one does not already exist. This is required for the automatic Flexible Sync subscription.

If you need to make updates to your client code after migration, consider updating your client codebase to remove hidden migration functionality. You might want update your client codebase when:

• You add a new model or change a model in your client codebase

• You add or change functionality that involves reading or writing Realm objects

• You want to implement more fine-grained control over what data you sync

Make these changes to convert your Partition-Based Sync client code to use Flexible Sync:

• Update your SyncConfiguration.Builder to use Flexible Sync. This involves removing the partitionValue and adding a set of initial subscriptions, if needed.

• Add relevant properties to your object models to use in your Flexible Sync subscriptions. For example, you might add an ownerId property to enable a user to sync only their own data.

• Remove automatic Flexible Sync subscriptions. If you did not add initial subscriptions in the SyncConfiguration.Builder, manually create the relevant subscriptions.

For examples of Flexible Sync permissions strategies, including examples of how to model data for these strategies, refer to Device Sync Permissions Guide.