Limitation for number of changes per one change request in CloudKit extension

[SofteqDG]

Ability to set the limit for number of changes per one change request in YapDatabaseCloudKitOptions. This can be used to fix "Invalid Arguments" (12/1020); "Your request contains more than the maximum number of items in a single request (400)" error. Discussion in #212.

[triplef]

We were running into the same issue and have been using this patch for several years in production. Would be great to get this merged. 👍

[gcox]

@robbiehanson Can you weigh in on this, please? Maybe I'm misunderstanding #212, but it sounds like if this issue is encountered when registering the extension there is no way around the problem and CloudKit syncing is effectively broken without a change like the one in this PR. Is that correct?

[robbiehanson]

The "max of 400" problem can be encountered in multiple scenarios:

• when registering the extension, and populating it with a large number of items
• when importing a large number of items within a single transaction

This PR limits the maximum number of changes that can be pushed to the cloud in a single request. This would seem to solve the issue. However, I haven't merged this pull request because, as I understand it, the PR does its limitation in an "arbitrary" manner. Whereby "arbitrary", I mean that it doesn't take into account CKReferences.

I suggested in #212 :

Fix the internals of YapDatabaseCloudKit to automatically split a ChangeSet into a maximum of 400 items. And do so in a safe way that allows us to take into consideration CKReferences.

So if A has a CKReference to B, and the ChangeSet is split like so: [..., A] [B, ...], we're going to get an error from the server. Its been awhile since I've worked with CloudKit, so let me know if I'm off on this.

[gcox]

@robbiehanson Thanks for your input. Your description is correct. I have an idea for addressing that problem so I'll look into it soon.