On 22 Apr 2009, at 22:34, Melissa J. Turner wrote:
On Apr 22, 2009, at 02:12, Mike Abdullah wrote:
On 22 Apr 2009, at 08:48, Ben Trumbull wrote:
Of course, why Apple couldn't have then added automatic support
for in-memory matching as the second step I don't know
Probably because nobody ever cared enough to file an enhancement
request, and it didn't occur to us that writing 1 line of code to
call filteredArrayWithPredicate was so troublesome.
Calling -filteredArrayWithPredicate is no hassle, but for a large
predicate, it has the bad performance of comparing a bunch of the
persistent properties all over again, despite already knowing
they'll match the predicate. Since I assume Core Data must do some
kind of internal splitting up of the predicate in order to perform
its fetch, I'd have thought it is in a good position to know what
the remaining transient portion of the predicate is.
You assume incorrectly.
CoreData simply translates the predicate to SQL and passes it down
to SQLite as a WHERE clause. Hence the lack of support for transient
properties: SQLite has no idea what to do when you ask it to qualify
by a column that doesn't exist in its schema.
OK, so I'm trying to wrap my head around this. Let's say I build a
predicate along the lines of:
fooPersistent == 123 && fooTransient == 456
And then use it in a fetch request. Does Core Data:
A) Pass that predicate straight to SQLite which fails because it can't
find a fooTransient column.
B) Pass that predicate straight to SQLite which ignores fooTransient
(presumably treating it as always evaluating to true).
C) Create a "fooPersistent == 123" predicate and pass that to SQLite.
Or of course D) something I've failed to conceive of which seems quite
probable!
Regards,
Mike.
_______________________________________________
Cocoa-dev mailing list (Cocoa-dev@lists.apple.com)
Please do not post admin requests or moderator comments to the list.
Contact the moderators at cocoa-dev-admins(at)lists.apple.com
Help/Unsubscribe/Update your Subscription:
http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com
This email sent to arch...@mail-archive.com
