I’ve had at least two readers reporting a problem a thumbnail rebuild issue. If this sounds like something you’re running into, please try the solution below and let us know in the comments if it did or didn’t help — or if you have any kind of related problem.
On every launch, Aperture starts rebuilding thumbnails (even though it doesn’t appear to need to). If you stop the rebuild, all is fine, but it will start up again on next launch. Odds are it’s always starting with the same number of images to rebuild; i.e. you see 78,415 thumbnails rebuilding, and you have 120,000 image in your library. So it’s likely not all of them, but most of them. Or more accurately, a single bad apple that’s ruining the batch.
You may have tried repairing permissions, repairing and rebuilding the database… trashing preferences… repairing hard drive… reinstalling Aperture… and more, all to no avail. You’ve tried manually rebuilding the thumbs, letting it complete, but it still starts over on next launch. Ugh!
Well, this worked for one customer — hopefully it will work for you, too.
What ultimately worked for one customer was to Consolidate Originals on the entire library — this means copying all referenced photos into the library, making it managed. At that point, the problem disappeared. In the process of consolidating, a small handful of images turned out not to be found, even though prior to this Aperture was reporting no offline or missing photos. Fortunately those few missing originals were not of importance, and the customer deleted them from his library.
Side note: I’ve noticed before that when you Consolidate or Relocate Originals, sometimes Aperture will identify missing Originals that it otherwise hadn’t noticed. It seems that this is the most thorough method to analyze the connection to your Originals, which makes sense — Aperture can’t move them if it can’t find them — and so is a sure-fire way to identify any missing or broken connections.
Once this consolidation was complete, the customer was able to Relocate Originals again to another location, and the problem stayed gone.
Therefore, I’m of the mind that simply Relocating Originals will have the same effect, and would certainly be easier and faster to perform. You could probably even do it to the same drive — just relocate from one folder to another, which would be very fast. You will still need sufficient free space for this though; I believe Aperture won’t even start unless it sees more than the space it needs for the entire relocate, even though it ultimately won’t need any more space than it started with.
If you do need to Consolidate to make the problem go away, you may be needing a very big disk with lots of free space. Fortunately external hard drives are cheap right now so hopefully this won’t be too painful if that’s the route you have to take.
Again, let us know if you have this problem, and if this fixes it, in the comments!