Hi Jeremy,
There are often situations where you want to do subselects with associated
tables, like getting a count from a has_many association:
Quiz.select_append(Question.where(quiz_id: :quizzes_id).select{count{}.*}.as
(:questions_count))
However, I don't like here that you need to repeat the ID joining. If you
specified `Quiz.has_many :questions`, the Quiz class already knows what is
the associated class, and how are the foreign and primary keys matched. So
it doesn't feel DRY.
I read an answer that you gave to one previous question
<https://groups.google.com/forum/#!topic/sequel-talk/muJ14cXsnpA>, where
you gave 3 different ways how to get a count for a has_many associations.
However, I find it a bit difficult to wrap my head around using joins and
grouping for this task, I would much rather use subselects.
My proposition would be do add something like
Sequel::Model.association_select, so that you can do
class Quiz < Sequel::Model
has_many :questions
dataset_module do
def with_questions_count
select_append(association_select(:questions).select{count{}.*}.as(:
questions_count))
end
end
end
So, `association_select(:questions)` here would be an equivalent of
`Question.where(quiz_id: quizzes_id)`. For the partical case of counts, I
decided that I'm much better of with counter caches (using
sequel_postgresql_triggers), but for other subselects I would love this
feature. I think it really shines when you have more complex associations,
for example with custom datasets, using pg_array_associatons etc.
What do you think about this idea?
--
You received this message because you are subscribed to the Google Groups
"sequel-talk" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to [email protected].
To post to this group, send email to [email protected].
Visit this group at http://groups.google.com/group/sequel-talk.
For more options, visit https://groups.google.com/d/optout.
