2009/8/31 Tony <[email protected]>: > > Maybe I'm missing something but I don't see any way to get eager > loading with the named scopes. I have many Event models each with > many Stat models. If I have to query each event to get the summary, I > still have the n+1 query problem.
Don't follow you here, it should be just one query for each event to get the stat summary for that event. Colin > Maybe the best solution is to > define a second model referencing the same table but with a different > default scope? That doesn't seem like it is the most concise solution > but it may be the cleanest and easiest to read. > > I think the ideal solution would be the ability to reference a named > scope of a joined model. E.g: > > Event: > has_one :summary, :class_name => 'Stat', :scope => :summary > > Does that make sense? Is there some other way that I'm overlooking? > Thanks again! > > tony > > On Aug 30, 2:36 pm, Tony <[email protected]> wrote: >> Thanks for the quick response! I'm not familiar with the named >> scopes. Will these work with preloading the records (I assume by >> using (:include => [:stats])? I could end up with a ton of Events on >> one page and I'd prefer not to have to fetch the summary for every >> one. I also assume I'd reference it by doing event.stats.summary? >> That seems a lot cleaner. I'll go dig into this a bit. Thanks! >> >> tony >> >> On Aug 30, 2:24 pm, Colin Law <[email protected]> wrote: >> >> > 2009/8/30 Tony <[email protected]>: >> >> > > So I'd like to set up the below associations. An Event is a normal AR >> > > model. Stat is a normal AR model. I want a special stat on Event >> > > that is a DB computation (mostly just sums of each column) and a >> > > summary of all the Stats for that Event. The Summary isn't persisted >> > > and is marked as readonly. Unfortunately, preloading is important in >> > > this case (and thus why I went off on the group_by tangent, sorry if >> > > that wasn't clear). >> >> > > I guess I could make a new model for Summary referencing the stats >> > > table which uses a special select and always adds the group by clause, >> > > however, that seemed like overkill. I really didn't want to run a >> > > loop over the returned stats since the DB can give me exactly what I'm >> > > looking for on the initial query. >> >> > > Ok, here's a slightly abridged version of what I thought might work: >> >> > > Event: >> > > has_many :stats >> > > has_one :summary_stat, :select => "sum(people) as >> > > people, ...", :class_name => 'Stat', :foreign_key => >> > > 'event_id', :readonly => true >> >> > > Stat: >> > > belongs_to :event >> >> > > Adding "group" to the has_one solves the issue, but am I going about >> > > this in the "right" way? Thanks for the input! >> >> > > tony >> >> > I don't think I would go about it this way. Using Event has_one >> > summary_stat suggests that somewhere there is a model SummaryStat that >> > belongs_to event. >> > An alternative would be to define an appropriate named scope in Stat >> > that provides the summed stats using the single query and provide a >> > read only attribute of Event that calls it and provides the answer. >> >> > Colin > > > --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en -~----------~----~----~----~------~----~------~--~---
