Offline-only Usage
Some use cases require data persistence before the user has registered / signed in. In some of those cases, the user may want to register and start syncing data with other devices or users at a later point, while other users may keep on using the app without ever registering or going online.
PowerSync fully supports these scenarios. By default, all local changes will be stored in the upload queue, and will be uploaded to the backend server if the user registers at a later point.
A caveat is that if the user never registers, this queue will keep on growing in size indefinitely. For many applications this should be small enough to not be significant, but some data-intensive applications may want to avoid the indefinite queue growth.
There are two general approaches we recommend for this:
1. Local-only tables
Use local-only tables until the user has registered or signed in. This would not store any data in the upload queue, avoiding any overhead or growth in database size.
Once the user registers, move the data over to synced tables, at which point the data would be placed in the upload queue.
An example implementation is coming soon.
2. Clearing the upload queue
The upload queue can be cleared periodically (for example on every app start-up), avoiding the growth in database size over time. This can be done using:
It is up to the application to then re-create the queue when the user registers, or upload data directly from the existing tables instead.
A small amount of metadata per row is also stored in the ps_oplog table. We do not recommend deleting this data, as it can cause or hide consistency issues when later uploading the data. If the overhead in ps_oplog is too much, rather use the local-only tables approach.
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