Wow, the COUNT approach is *really* inefficient compared to the IN subquery, it totally makes sense never to use it :P
Would you perhaps be open to adding a `Sequel::Model.association_dataset` method some time in the future that would retrieve the `eager_loading_dataset` (called with `.association_dataset(:association)`)? I think it would be nice alternative, as it would allow one to avoid duplicating any conditions and ordering configured for the association. I don't think we'd have any real use for it at the moment, because we only have max of one condition on our associations, so it's not a problem to duplicate them. But I was just wondering, should ever want to have this feature in the future, would you accept a PR for that. Thanks for your help! Kind regards, Janko On Thu, Sep 13, 2018 at 4:00 PM Jeremy Evans <[email protected]> wrote: > On Thursday, September 13, 2018 at 2:53:23 AM UTC-7, Janko Marohnić wrote: >> >> Hi Jeremy, >> >> Is there a way to fetch the association dataset from the model/dataset >> level, which can then be used for making subqueries? To illustrate, let's >> assume the following association declarations: >> >> class Album < Sequel::Model >> end >> >> class Artist < Sequel::Model >> one_to_many :released_albums, class: Album, conditions: { released: >> true } >> end >> >> And let's say that I would like to fetch all artists that have at least >> one released album. Currently I would do it like this: >> >> released_album_count = Album >> .where{albums[:artist_id] =~ artists[:id]} >> .where(released: true) >> .select{count.function} >> >> Artist.where(released_album_count > 0).to_a >> >> However, I feel like here I'm repeating many things (album class, foreign >> key matching, released condition) that are already declared in the >> :released_albums association. Is there any way that I can use the >> :released_albums association to create such a dataset? So that I can do >> just something like: >> >> # here I'm using an imaginary "association_dataset" method >> released_album_count = >> Artist.association_dataset(:released_albums).select{count.function} >> >> Artist.where(released_album_count > 0).to_a >> > > I'm guessing this may work in terms of returning an associated dataset: > > > Artist.association_reflection(:release_albums).send(:eager_loading_dataset) > > As you can guess, eager_loading_dataset is a private method. > > For what you are doing, I would use a IN subquery, since you don't care > about how many there are, just that at least one matches: > > Artist.where(:id=>Album.where(:released).select(:artist_id)) > > Thanks, > Jeremy > > -- > You received this message because you are subscribed to a topic in the > Google Groups "sequel-talk" group. > To unsubscribe from this topic, visit > https://groups.google.com/d/topic/sequel-talk/Na7HQji-Y_k/unsubscribe. > To unsubscribe from this group and all its topics, send an email to > [email protected]. > To post to this group, send email to [email protected]. > Visit this group at https://groups.google.com/group/sequel-talk. > For more options, visit https://groups.google.com/d/optout. > -- 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 https://groups.google.com/group/sequel-talk. For more options, visit https://groups.google.com/d/optout.
