Parse.com：本地缓存有多大？

Question

Parse.com handles local caching, which is great.

How large may the local cache become on an iOS device? In the online doc , Parse states:

Parse takes care of automatically flushing the cache when it takes up too much space.

If I store thousands of objects in Parse,and would like to cache them all locally, would that work? What is the cache limit?

Also is there a limit per entity or a global limit for all entities?

Thank you!

Answer 1

It sounds like you are looking to be able to use your Parse data offline. I'm not certain of the size of the Parse cache or the details of how it works. I have some experience using Parse and ran into some issues with this very topic. I think it's important to note that in Parse's documentation they describe that they "cache the result of a query on disk." This is very different from caching all of your PFObjects on disk.

Essentially the cache allows you to re-run a query that has already been run and get the same results as the first time. For example, you can't cache the results of a query that returns all of a certain object type and then later run another query that gets a subset of those objects from the cache. You have to run the exact same query to get the cached result. This can be very limiting.

I gave up on relying on Parse's cache before testing any of this, but I believe using it heavily can be dangerous. For example, if you retrieve a cached query result, edit one of the PFObjects, and then retrieve the same cached query result again I am pretty sure the PFObject you edited will not reflect your edits. I could be wrong about this, but you could test it easily enough.

As I said, I gave up on relying on the Parse API for offline use. I ended up using Core Data as the local store for my data and syncing my NSManagedObjects with Parse. In my case I needed everything to work when offline. There may be a better way to handle this, but I haven't seen one.