title: Find hash attribute value on active record rails
body: <p>I am developing the application with Ruby on Rail. As in my current project I have an active record model as an example below :</p>
  
  <pre><code>&lt;Site id: 6241, collection_id: 7, name: "ABC", properties: {"31"=&gt;20}&gt;
  &lt;Site id: 6242, collection_id: 7, name: "ABC", properties: {"10"=&gt;20}&gt;
  &lt;Site id: 6243, collection_id: 7, name: "ABC", properties: {"11"=&gt;30}&gt;
  </code></pre>
  
  <p>However, I want to find the site which has the properties with the key '31' and value 20, but I cannot find the way to compare this hash attribute. So is there any way you could suggest me?</p>