从数据库记录添加一个新的字段到每个现有的哈希散列更新的数组 [英] Update an array of hashes with records from the database adding a new field into each existing hash

问题描述

我有一个名为记录与哈希千阵列（见第一阵列，​​显示如下）。目前，每个哈希包含两个字段 ID 和 PARENT_ID 。我想补充的updated_at 一个新字段存储在数据库中（请参阅下面的第二个阵列）。

I have an array called records with thousand of hashes (see the first array showed below). Every hash contains currently two fields id and parent_id. I want to add a new field called updated_at which is stored in the database (see the second array below).

records = [{"id"=>3, "parent_id"=>2}, 
           {"id"=>4, "parent_id"=>2}]

records = [{"id"=>3, "parent_id"=>2, "updated_at"=>"2014-03-21 20:44:35 UTC"}, 
           {"id"=>4, "parent_id"=>2, "updated_at"=>"2014-03-21 20:44:34 UTC"}] 

我的第一种方法是以下步骤之一，但它执行查询的数据库，每一个哈希，所以如果我有1K哈希数组中，它要执行1K疑问，我认为这是不是从很好性能上来看。

My first approach is the following one, but it executes a query to the database for every hash, so if I have 1K hashes in the array, it is going to execute 1K queries, which I think is not very good from the performance point of view.

records.each do |record|
  record['updated_at'] = Record.find(record['id']).updated_at.utc.to_s
end

您能否提供我一个更好的解决方案？

Can you suggest me a better solution?

推荐答案

怎么这样呢？散了查询，通过聚合的IDS片的时间。调整 each_sli​​ce 量的东西，表现良好......

How about something like this? Bulk up the queries by aggregating the ids a slice at a time. Adjust each_slice amount to something that performs well...

records.each_slice(250) do |records|
  ids = records.map { |r| r['id'] }
  results = Record.select([:id, :updated_at]).find(ids)
  records.each do |rec|
    result = results.find { |res| res.id == rec.id }
    rec['updated_at'] = result.updated_at.utc.to_s
  end
end

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