Hey all, I've been playing around with special relationships (specifying the select, etc) on my models and trying to get Rails to return the results of database computations as part of an association. I've got one model representing an object and another model representing statistics about that object on per day basis. That main Event object has many Stats but it also has one Summary (of those Stats). Unfortunately, Rails won't allow me to have a has one association with computed columns (sums in my case) since it will not allow the use of the group by clause without which Rails can't connect the returned stats to the event since the event_id column is null. I've gotten around this by using a has_many association for the stats even though I'm grouping on the foreign key and will only ever have one record at most. This creates some really "hacky-looking" code since I have to read the first element of the returned array everywhere to read the summary stats. I went digging through the Rails source to take a look at why this might be prevented and I've come up with two thoughts:
1) Rails should allow use of :group for a has_one association for specific use cases such as this one and let the programmer decide how it works. The fix is as simple as adding it to the valid_keys_for_has_one_association in associations.rb. However, this lead me to a second thought... 2) In a has_one association it seems like it would never be detrimental to use a group by clause on the foreign key as this would always return one or fewer results for the parent table. This relates to the comment at association_preload.rb:148 (in 2.3.3) which states that there is no way to ask the database for one row per distinct foo_id (which is what group by would do, at least in MySQL). Am I missing something or is this something that ought to be patched? Thanks for the input and help! tony --~--~---------~--~----~------------~-------~--~----~ 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 -~----------~----~----~----~------~----~------~--~---
