Thank you, I'll check this out. On Thursday, January 14, 2016 at 1:13:36 AM UTC+8, Jim wrote: > > On Wednesday, January 13, 2016 at 2:22:51 AM UTC-5, Lei Zhang wrote: >> >> I am going to implement a small and simple search feature in my project. >> But got a question about the scenario I have right now. So hope to get some >> tips from here. >> >> First of all, this is a rails app. >> >> There are two models, A and C. >> >> A has_many C. >> >> That's to say, it might have some situation like this: >> >> A1 related to C1, C2, C3, C4 >> A2 related to C2, C3, C4, C5 >> A3 related to C2, C3, C4, C8 >> A4 related to C3, C4, C8, C9 >> A5 related to C4, C8, C9, C20 >> >> Use C2, C3, C4 as keyword, I can get A1, A2, A3 >> Use C4, C8, C9 as keyword, I can get A4, A5 >> >> I consider that this can be done by using something straightforward like >> A.Cs.includes?(C2,C3,C4). >> >> But that requires an iteration of A. And I concern that it would have >> some performance issue. >> > > If you want to load matching As without instantiating the Cs, you could do > something like: > > A.where(id: C.where(code: params[:codes]).pluck(:a_id)) > > If you are going to instantiate all As and Cs found anyway, you could just > use eager loading: > > found_c = C.where(code: params[:codes]).includes(:a) > found_a = found_c.collect(&:a).uniq > > Jim >
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