RE: Question regarding nullified relationship objects
RE: Question regarding nullified relationship objects
- Subject: RE: Question regarding nullified relationship objects
- From: "Jon C. Munson II" <email@hidden>
- Date: Mon, 9 Feb 2009 15:31:22 -0500
- Organization: JTA Enterprises LLC
Namaste!
Thanks Ben!
I just wanted to make sure I wasn't left with "orphans" hanging around that
would require later maintenance...
To I.Savant: Actually, I am curious to know from the perspective of either
the XML type or SQLite type. However, Ben's response provided the needed
answer, which is that there isn't anything left hanging around with which to
bother.
Peace, Love, and Light,
/s/ Jon C. Munson II
> -----Original Message-----
> From: Ben Trumbull [mailto:email@hidden]
> Sent: Monday, February 09, 2009 3:15 PM
> To: Jon C. Munson II
> Cc: Cocoa Developers
> Subject: re: Question regarding nullified relationship objects
>
> > If I have two entities, A and B, where A <-->>B, and the delete rule
> > in
> > entity A's relationship to B is cascade, and B's delete rule for the
> > relationship to A is nullify, what happens to the actual "row" that
> > holds
> > the relationship data in A that was once B after B is deleted? Does
> > it get
> > completely deleted, or is it left as garbage that is later cleaned
> > up, or is
> > left and later re-filled?
>
> If you delete B first, it nullifies the inverse, and A remains alive
> and well. A will then have NULL for its column referring to B's
> table. If you delete A first, it cascades the deletion, and
> everything will be deleted.
>
> > what happens to the actual "row" that holds the relationship data in
> > A that was once B after B is deleted?
>
> The stuff is deleted. Often it's not a row. There might be a join
> table, or there might not. "Implementation dependent" For
> educational purposes only, if you want to get a better feel of what's
> going on, you can use -com.apple.CoreData.SQLDebug 1 as a user
> default. I prefer the command line like:
>
> some.app/Contents/MacOS/some -com.apple.CoreData.SQLDebug 1
>
> Unlike .NET, the association tables are not first class objects of
> their own, but rather just a property on the source object.
>
> - Ben
>
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