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: Jeffrey Oleander <email@hidden>
- Date: Sun, 7 Mar 2010 10:58:08 -0800 (PST)
> On Sat, 2010/03/06, Joanna Carter <email@hidden> wrote:
> This quote from the Core Data Programming Guide:
> ////////////////////
> There are some interactions between fetching and
> the type of store. In the XML, binary, and
> in-memory stores, evaluation of the predicate and
> sort descriptors is performed in Objective-C with
> access to all Cocoa's functionality, including
> the comparison methods on NSString.
> The SQL store, on the other hand, compiles the
> predicate and sort descriptors to SQL and
> evaluates the result in the database itself.
> This is done primarily for performance, but
> it means that evaluation happens in a non-Cocoa
> environment, and so sort descriptors (or
> predicates) that rely on Cocoa cannot work.
> ////////////////////
>
> To my mind, this does state exactly what you have found.
? Sounds like 10% information and 90% hand-waving
with no "exactly" about it.
The reasonable thing to have in the doc after this
is more precise descriptions of the differences,
with several examples to show how it would work
with and without SQL.
But... after several tries searching from the doc
home page, fighting the Evil Fremd Javascript,
finally finding the right doc, reading through the
page, I filed feed-back against the doc page.
You should probably file your own, because the
likelihood that we'd say things the same way,
expressing exactly the same concern, including
the same things and leaving out the same things,
is tiny.
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