更新Rails 4和PostgreSQL json列中的单个键/值对？

Question

我有一个相当大的json文档,我必须存储在我的应用程序中的每个Evaluation实例的字段中.随着时间的推移,应用程序上的某些操作将要求我更改文档中的各种键/值对.Rails 4和PostgreSQL json数据类型似乎是这个问题的理想选择,但我无法对数据库进行更改.

这是一个缩写的工作流程:

我有一个json文件,我导入每个评估记录的字段:

// example.json
{ "question_1":"no" }

我创建一个记录并导入json:

>> evaluation = Evaluation.create assessments: File.read("example.json")
>> evaluation.assessments = File.read("#{Rails.root}/example.json")
=> "{ \"question_1\":\"no\" }"

调用评估字段似乎工作正常:

>> evaluation.assessments
=> {"question_1"=>"no"}

OR

>> evaluation.assessments["question_1"]
=> "no"

例1

改变json不是很好.这实际上没有提交任何东西:

>> evaluation.assessments["question_1"] = "yes"
=> "yes"

>> evaluation.assessments["question_1"]
=> "yes"

>> evaluation.save
   (0.3ms)  BEGIN
   (0.2ms)  COMMIT
=> true

例#2

替换为一个全新的对象确实提交:

>> evaluation.assessments = {"question_1"=>"yes"}
=> {"question_1"=>"yes"}

>> evaluation.save
(0.3ms)  BEGIN
SQL (0.7ms)  UPDATE "evaluations" SET "assessments" = $1, "updated_at" = $2 WHERE "evaluations"."id" = 1  [["assessments", "{\"question_1\":\"yes\"}"], ["updated_at", "2014-08-21 00:52:03.581817"]]
(3.8ms)  COMMIT
=> true

• 我在示例#1中做错了什么？
• evaluation.assessment当我调用它时,为什么数据库不会提交我对列所做的更改,更改值,并在实例上调用save？

Answer 1

由于与ActiveRecord相关的已知错误不知道更改的属性是脏的,因此最终成为一个简单的修复:

https://github.com/rails/rails/issues/6127

这是解决方案:

>> evaluation.assessments["question_1"] = "yes"
=> "yes"

>> evaluation.assessments_will_change!
>> evaluation.save
(1.1ms)  BEGIN
SQL (1.6ms)  UPDATE "evaluations" SET "assessments" = $1, "updated_at" = $2 WHERE "evaluations"."id" = 4  [["assessments", "{\"question_1\":\"yes\"}"], ["updated_at", "2014-08-21 01:59:47.331216"]]
(2.5ms)  COMMIT
=> true