From: Ryan Pavlik <rpav@...>
Date: 2004-01-09T19:11:04+09:00
Subject: Re: Query syntax in O-R mapping (was: Database applications and OOness)

On Fri, 9 Jan 2004 13:41:44 +0900
sera@fhwang.net (Francis Hwang) wrote:

<snip bits about Criteria hackage ;-)>
> Here's my concern: Seems to me than when you have a syntax that
> looks _sort of_ like normal Ruby, but is different in all these tiny
> subtle ways, using it might involve a lot of "mental housekeeping"
> about why things work and don't work. In particular, the idea of
> teaching a moderately skilled programmer how to use Criteria is
> pretty daunting.

Well, for me, it comes down to Criteria---albeit not perfect,
especially in the ways you mentioned---being better than embedding SQL
text into Ruby.  Secondly, it's an abstraction, which means primarily
it doesn't necessarily generate SQL, which is useful (at least in
theory).

> Is this not a problem for Criteria users? Am I just worrying too
> much?

Of course "it's less bad" doesn't answer your question.  I'd say you
only need to be especially aware of 2 things to use Criteria:

    1)  Method operators (&, |, etc) vs syntax operators (&&, ||, etc)
    2)  Operator precedence

The latter isn't really so much of an issue either, at least for
me... I tend to explicitly specify parens anyway, just because I like
the way it looks on the screen.

This isn't to say Criteria isn't tricky.  To be honest, because of the
way it wraps back into the language, there are a lot of weird things
that you can do, and a lot of things that happen "magically".  I don't
think anyone has to wrap their head around the whole thing to use it,
though.  (At least, I hope not, because I use it, and I don't always
see all the possibilities. ;)

I can't come up with a better way to integrate abstract query
notation, though.  I've tried other various things and they're all
uglier.  That's not to say someone smarter can't come up with
something simpler and more flexible.  They just need to implement it
for us. ;-)

-- 
Ryan Pavlik <rpav@mephle.com>

"You mean easily pawned valuable crystal orb thingie." - 8BT