Mongoid:通过ID数组查找 [英] Mongoid: find through Array of ids

问题描述

我已经通过MapReduce提取了许多ID.我已经按照某些条件对这些ID进行了排序，现在我需要按照以下特定顺序来获取这些对象:

I've fetched a number of ids through MapReduce. I've sorted those ids by some criteria and now I need to get those objects in this particular order:

MyModel.find(ids)

对吗?但是它返回的对象不是按存储顺序ID的顺序.看起来和

Right? But it returns objects not in the order ids are stored. Looks like this is just the same as

MyModel.where(:_id.in => ids)

不会以与存储的id相同的顺序返回获取的对象.

which won't return fetched objects in just the same order as stored ids.

现在我可以做到

ids.map{|id| MyModel.find(id)}

这可以完成工作，但是会多次破坏数据库.

which will do the job but it will knock the database many many times.

推荐答案

在拥有所有对象之后，您可以手动进行排序.像这样:

You can do the ordering by hand after you have all your objects. Something like this:

ordering = { }
ids.each_with_index { |id, i| ordering[id] = i }
objs = MyModel.find(ids).sort_by { |o| ordering[o.id] }

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