On 02/13/2015 02:12 PM, thilo.fes...@googlemail.com wrote:
...
{
from => [
{ 'me' => 'artist' },
[
{ 'tracklíst' => $track_list_rs->as_query },
{ 'me.artistid' => { -ident => 'tracklíst.artistid'
} },
]
],
(comment unrelated to your original question): Note that the above usage
is unsupported (specifying a from structure by hand may or may not work
this way). I literally can not tell if there are corner cases with the
above or not without studying the source code for good 5 minutes. I
understand there is no easy way to specify this stuff on the fly
currently, read on for details why there is yet no defined API for that.
In any case - make sure you test and comment this part of your code
heavily - this *will* stop working in the distant future.
Here I simply want to build a list of tracks per artist and connect it
to the artist directly.
For prefetching the tracklist, I use '+columns' and 'collapse', because
I expected those two not to check for the accessor "tracklist" (but this
seemed to be a wrong assumption).
The issue here isn't the accessors, but the relationship between "left
and right side". collapse => 1 needs to know a lot of metadata about the
'tracklist' to determine how to properly "fold" it when it sees
repetitions of the same data (is it a duplication as a result of another
join, or is it just multiple identical titles?). Currently this metadata
can only be gleaned via
$schema->source('Artist')->related_source('tracklist'). Since there is
no such thing you get an exception (I need to improve the text of that).
In essence your best bet is to define a real relationship to "tracklist"
with the correct subquery and everything, like in this example:
https://github.com/dbsrgits/dbix-class/blob/current/for_cpan_index/t/lib/DBICTest/Schema/CD.pm#L120-L154
If you are interested in the inner logic that collapse => 1 triggers, it
can be found in this "double-recursion" function:
https://github.com/dbsrgits/dbix-class/blob/current/for_cpan_index/lib/DBIx/Class/ResultSource/RowParser.pm#L149-L398
If this reply isn't sufficient to answer your question - please ask further.
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