On Tue, Apr 26, 2011 at 09:51:30PM +0200, Arthur Taylor wrote:
> Aaron, all,
>
> Did anyone have any strong feelings about the following feature - is it
> something that it's going to be possible to get included (possibly in a
> prettied up form), or am I better forking / monkey-patching?
> > The idea with the placeholders is that you could have one query which
> > serializes differently to SQL (or through any of the visitors)
> > depending on the dynamic value of the placeholders. The effect I want
> > (and am using in my local repo) is not to have to define the values of
> > all the query terms at query build time:
> >
> > @placeholders = { :username => "bob" }
> >
> > query =
> > @users.project(@users[:id]).where(@users[:name].eq(Arel::Nodes::Placeholder.new(:username,
> > @placeholders)))
> > query.to_sql => "SELECT `users`.`id` FROM `users` WHERE
> > `users`.`name` = 'bob'"
> >
> > @placeholders[:username] = "adam"
> > query.to_sql => "SELECT `users`.`id` FROM `users` WHERE `users`.`name`
> > = 'adam'"
> >
> > Make sense? Sound useful? I'm not sure that's the most elegant API in
> > the world (in fact I'm pretty sure it's not), but I'm open to
> > suggestions as to pretty ways to achieve the same thing.
> >
> The other design I considered would be:
>
> @placeholders = Arel::Placeholders.new(:username => "bob")
>
> query =
> @users.project(@users[:id]).where(@users[:name].eq(@placeholders.for_key(:username)))
> query.to_sql => "SELECT `users`.`id` FROM `users` WHERE `users`.`name`
> = 'bob'"
>
> @placeholders.update(:username => "adam")
> query.to_sql => "SELECT `users`.`id` FROM `users` WHERE `users`.`name` =
> 'adam'"
>
> which seems a little more elegant.No, I don't want to include this in ARel. ARel manages an SQL AST. Since "Placeholder" isn't part of SQL, I don't want to support it. But that doesn't mean you can't subclass the visitor and add it, or monkeypatch the ToSql visitor and add support. I certainly won't break that. -- Aaron Patterson http://tenderlovemaking.com/
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