Re: How to manage a separate data file while saving an NSPersistentDocument or during schema migration
Re: How to manage a separate data file while saving an NSPersistentDocument or during schema migration
- Subject: Re: How to manage a separate data file while saving an NSPersistentDocument or during schema migration
- From: Quincey Morris <email@hidden>
- Date: Fri, 16 Jan 2009 18:58:42 -0800
On Jan 16, 2009, at 17:26, Barry Wark wrote:
In fact, that's how I started. It works fine (using a separate entity
for the data), and performance was fine. Unfortunately, the backup
system at the deployment site backs up entire changed files (rather
than binary diffs), so the continuous changes to flags and metadata in
the data model during analysis force a back up of all the original
BLOB data as well... order 100GB/day. Thus, we've decided to go with
the separate file solution. Since this is, in fact, the Apple
recommended approach, I was surprised it wasn't easier to implement.
If the BLOBs themselves are not being changed (at least by this
application on a per-document basis), then you could keep a "library"
of BLOB sets in the Application Support folder or somewhere shared.
Or, even if the BLOBs are changed sometimes, you could try putting
them in a separate persistent store that you add to your managed
object context, and use cross-store links. It's *possible* that a
simple Save will not touch the BLOB store if the BLOBs haven't changed
(though I have no idea if that's so or not). In that case, your backup
system won't try to backup the unchanged store. You'd have to try this
out for feasibility, and it means messing with cross-store links, but
the big win is of course that you don't have to get your hands dirty
in the save process at all (I think).
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