Re: Join splits

[Mike Kienenberger <mk...@gmail.com>]

Aliases seem like a good idea.   I know that when I implemented all of
this, internally I had to set up an alias table, so it's a natural
fit.

On 4/30/08, Andrus Adamchik <an...@objectstyle.org> wrote:
> Now looking to add splits to SelectQueries, I am wondering if the approach
> we discussed before is too "special case". To reiterate, the idea of a "join
> split" (CAY-802), was to allow users to override the default behavior of
> Cayenne which is to reuse all joins. Here is some in-depth discussion of
> useful split scenarios:
>
>
> http://objectstyle.org/cayenne/lists/cayenne-devel/2003/09/0096.html
>
>  I am wading through archives trying to find the pipe ("|") semantics that
> Giulio Cesare used for the splits, but IIRC it was something like this:
>
>     rel1.rel2|rel3.rel4
>
>  That's fine except that it is targeting a special case of matching a single
> path against a collection of values. A more generic case would be  multiple
> overlapping but different expression paths. E.g.:
>
>     rel1.rel2.rel3.rel4
>     rel1.rel2.rel3.rel5
>
>  Split semantics, while rather concise and clear for its intended use,
> doesn't help us in dealing with multiple overlapping paths... So how do we
> handle those? One possible solution is to follow EJBQL idea and define
> aliases for join paths. This way each alias for the same path generates a
> separate chain of joins that can be reused if needed. E.g.:
>
>  SelectQuery query = ...
>  query.addQualifierAlias("rel1.rel2", "a");
>  query.addQualifierAlias("rel1.rel2", "b");
>
>  Then the following can be used as qualifier:
>
>    a.x
>    a.rel4
>    b.y
>    b.rel5
>
>  Any thoughts on that? Would that be better than the pipe sign? (and did we
> discuss that before, and I am simply missing it)
>
>  Andrus
>
>