Has the repair mechanism changed for Photos libraries that are synced with iCloud?
It appears to me that perhaps the Photos library repair mechanism has changed, although I have no inside knowledge related to how Apple has implemented this. I have, unfortunately, been forced to repair my library several times over the years. In the past, there seemed to be a long period where all the items in my library were uploaded back to iCloud. My library is approximately 650 GB and contains approximately 62000 items. This upload process took many days and I could monitor the high network traffic with Activity Monitor.
This time, however, with macOS Catalina 10.15.5 the repair was performed much more quickly. It took only about two days and there was never a huge amount of network traffic. There was, however, a great deal of CPU activity and a relatively small amount of network activity throughout this repair process. If I had to guess, it might be that Photos is generating hashes (a type of checksum) of all of the items in my library, which Photos uploads to iCloud instead of the images and videos themselves. This is a perfectly valid way for Apple to confirm if the items in your Photos library on your Mac are identical with the same items stored in your iCloud Photos library.
At any rate, the important point to note is that the library repair completed much faster that it used to take and I never observed high network traffic. It would be interesting to know if anyone else has noticed a similar change.
iMac 27″, macOS 10.15
