Swift Couchbase Lite General Questions

Mobile Couchbase Lite
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We have a few questions about CBL and hope someone can provide some clarity

  1. Are Couchbase Swift objects lazy-loaded. We are migrating from MongoDB Atlas Realm and that’s a feature which became important to our use case. To provide context, here is how an object is defined in Realm

Realm uses lazy loading and memory mapping with each object reference pointing directly to the location on disk where the state is stored. This exponentially increases lookup and query speed as it eliminates the loading of state pages of disk space into memory to perform calculations. It also reduces the amount of memory pressure on the device while working with the data layer.

Apple implements lazy-loading with LazyVStack as an example and here’s a pretty accurate overview of the technology

  1. How are notifications presented? Suppose we are observing a collection of Users. A user changes his favorite food from Taco to Pizza. How does the app receive that? Is the object that change presented, or possibly a row # in the dataset so specific UI elements can be updated?

  2. With Realm, we could use Partition Sync or Flex Sync. Flex sync would enable the app to subscribe to certain objects only. Does Couchbase have that functionality or is it all or none. e.g. is everything sync’d?

Thank you - please let me know if anything needs clarity

Jay

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  1. Yes and no. We don’t use memory mapping, so getting a document reads its body from the database file into a heap block. However, it’s a single heap block (not an object tree) and is in an efficient binary format, significantly smaller than JSON. The Swift values returned from accessor methods are created lazily, so only as much of the JSON object tree is allocated as you use. (The same is true for query results: the Result object contains the results as a single compact binary block.)
  2. CBL has database/collection observers that will notify you when documents change. You can also observe specific documents by ID. A query observer will tell you when the result set of a query changes.
  3. You can pull specific channels of a server database. The Sync Gateway documentation explains channels.
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