Re: predicate for a Core Data fetch request rejected by SQL
Re: predicate for a Core Data fetch request rejected by SQL
- Subject: Re: predicate for a Core Data fetch request rejected by SQL
- From: "Sean McBride" <email@hidden>
- Date: Sat, 6 Mar 2010 21:17:32 -0500
- Organization: Rogue Research Inc.
On 3/5/10 5:52 PM, Mark Sanvitale said:
>However, my experience seems to demonstrates that the statement "We (the
>system) cannot necessarily translate "arbitrary" predicates into SQL
>queries" is also true,
It definitely is.
>and I believe this concept should be expanded to
>spell out exactly what generally legal predicates end up being illegal
>when applying them to a Core Data context that is backed by SQL. The
>only expanded discussion I can find on this subject in the official docs
>is, "predicates that rely on Cocoa cannot work", which, for me, does not
>shed enough light on the subject.
I agree the docs are weak here. I haven't looked in a while, but I
don't recall seeing a list of which types of predicate don't with the
SQL store. I've found this frustrating as I, like you, know nothing of SQL.
The tools are also weak here. I don't know of any way for the compiler
or static analysis tool to warn when a predicate will not work. But
you'll find out at run time. :) In my case, it was painful because we
switched from the XML store to the SQL store and it took a while to
shake out all the 'bad' predicates.
--
____________________________________________________________
Sean McBride, B. Eng email@hidden
Rogue Research www.rogue-research.com
Mac Software Developer Montréal, Québec, Canada
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