External storage for images

[gianpispi]

Looking ad SwiftData, it would be great to have some externalStorage attribute for image fields, that automatically and atomically move the image to the documents folder and insert the path to the db.
This could be an even bigger impact for this to work with CloudKit out of the box - I saw it works already with blob fields.

I just don't like to store big images inside the database itself

[mbrandonw]

Hi @gianpispi, we have plans to look into this, but can't commit on a timeline. Referencing files on disk from the database brings extra complications, and I'm not sure even SwiftData handles it correctly. For example, do you know what SwiftData does if one deletes the file from disk directly? Does SwiftData observe that and clean up the data in the database?

[aehlke]

The pattern I like from prior Realm<->CloudKit libraries is to store Data blobs on disk and use CKAsset for them automatically. The files are stored somewhere inaccessible to the user alongside the DB files so they can be expected to exist, with some kind of edge case error handling.

[mbrandonw]

That all sounds good in theory, but still comes with many complications.

For example, SwiftData works how you are describing, where you can use .externalStorage to say that some data should be stored on disk instead of in the DB. But then you can write a reasonable looking query, like #Predicate { $0.image.count > 1_000 } and it will actually crash at runtime because the data isn't really stored in the db, it's on disk. Even worse, small blobs of data are stored in the DB, and so that query could sometimes work and sometimes crash, giving you a false sense that you know how the system works.

All of this to say, we'd love to do something about this, but it really is not as easy as it seems at first. We think it is a better model to hold onto actual file URL's in the model rather than pretending that the data is held in the database.

[aehlke]

I see. As a Realm refugee I'm still learning about this tool.

An incremental improvement you can do is to use CKAsset for Data/blobs even if SQLite still stores the data

[mbrandonw]

An incremental improvement you can do is to use CKAsset for Data/blobs even if SQLite still stores the data

That is already supported: https://github.com/pointfreeco/sharing-grdb/blob/05c78647b5fdf5ae8b274da6f7f2934708963f00/Sources/SharingGRDBCore/Documentation.docc/Articles/CloudKit.md#Assets