Store images in sqlite or just a reference to it?

Question

I have made couple of apps using coredata and I was storing images in sqlite, but somewhere i found that it is bad. I've searched the net but all I've found is this suggestion:

• image size < 100kb store in the same table as the relevant data
• image size < 1mb store in a separate table attached via a relationship to avoid loading unnecessarily
• image size > 1mb store on disk and reference it inside of Core Data

So my question is: what are pros and cons of saving an image in sqlite db as NSData, and storing just a reference to the image while image is saved in the file system?

Answer 1

Apple provide some guidance on this topic in their guide on Core Data Performance. In general, although SQLite scales pretty well and can handle databases that are many gigabytes in size with ease, large binary blobs are not queryable or indexable, and inflate the size of the database with little return.

If you're targeting iOS 4 and above, you can set the "Allows External Binary Data Storage" flag on your attributes that contain such data, and Core Data will automatically store them separately on the file system (if it deems appropriate), and automatically manage the link to that data in your data store.