如何使用 postgresql 或 activerecord 在 Rails 中更新 json 字段的键名？答案

【问题标题】：How to update json field's key name in rails using postgresql or activerecord?如何使用 postgresql 或 activerecord 在 Rails 中更新 json 字段的键名？
【发布时间】：2020-12-23 03:32:22
【问题描述】：

我有一个名为cart 的表，其中items 属于json 类型。购物车中的值如下 3 个示例：

1. Cart(id: 1, name: 'Test', items: [{'desc'=>'First','names'=>'First'}, {'desc'=>'Second','names'=>'Second'}])
2. Cart(id: 2, name: 'Test', items: [{'desc'=>'First','names'=>'First'}, {'desc'=>'Second','names'=>'Second'}])
3. Cart(id: 3, name: 'Test', items: [{'desc'=>'First','name'=>'First'}, {'desc'=>'Second','name'=>'Second'}])

如何更新所有项目键以在 rails 中使用 name 键而不是 names？这样就变成了：

1. Cart(id: 1, name: 'Test', items: [{'desc'=>'First','name'=>'First'}, {'desc'=>'Second','name'=>'Second'}])
2. Cart(id: 2, name: 'Test', items: [{'desc'=>'First','name'=>'First'}, {'desc'=>'Second','name'=>'Second'}])
3. Cart(id: 3, name: 'Test', items: [{'desc'=>'First','name'=>'First'}, {'desc'=>'Second','name'=>'Second'}])

【问题讨论】：

标签： ruby-on-rails postgresql activerecord

【解决方案1】：

我认为这样的事情应该可行：

ActiveRecord::Base.connection.execute <<-SQL
  UPDATE cart t1
  SET items = (
    SELECT json_agg(
      el :: jsonb - 'names' || jsonb_build_object('name', el -> 'names')
    ) FROM cart t2, jsonb_array_elements(t2.items) as el
    WHERE t1.id = t2.id
  )
SQL

【讨论】：

【解决方案2】：

首先获取所有记录：

all_carts = Cart.all

#<:relation id: name: items:>

然后循环每条记录并更改json键：

all_carts.each do |cart|
  jitems = JSON.parse(cart.items) # ---> [{"desc"=>"First", "names"=>"First"}, {"desc"=>"Second", "names"=>"Second"}] 
  jitems.each { |it| it['name'] = it['names']; it.delete('names') } # ---> [{"desc"=>"First", "name"=>"First"}, {"desc"=>"Second", "name"=>"Second"}] 
  cart.items = jitems.to_json # ---> "[{\"desc\":\"First\",\"name\":\"First\"},{\"desc\":\"Second\",\"name\":\"Second\"}]"
  cart.save
end

【讨论】：