title: In Rails, Ransack search gives the error `PG::UndefinedFunction: ERROR: operator does not exist` when trying to filter by ID
body: <p>Im trying to filter the records by the <code>ID</code>. Here's my search form :</p>
  
  <pre><code>&lt;%= search_form_for @search, url: dash_orders_path, id: 'searchForm' do |f| %&gt;
      &lt;div class="col-md-4 margin-top-15"&gt;
          &lt;%= f.search_field :id_cont, class: 'form-control', placeholder: 'Order id' %&gt;
      &lt;/div&gt;
      &lt;span class="button-sec pull-left width-wide center-text searchBtn"&gt;
          &lt;%= f.submit "Search", class: "button-big blue" %&gt;
          &lt;%= f.submit "Clear", class: "button-big red", onclick: "$('#searchForm')[0].reset();" %&gt;
      &lt;/span&gt;
  &lt;% end %&gt;
  </code></pre>
  
  <p>When trying to do the search, it gives an error like this :</p>
  
  <pre><code>PG::UndefinedFunction: ERROR:  operator does not exist: integer ~~* integer
  LINE 1: ...CT  "orders".* FROM "orders" WHERE ("orders"."id" ILIKE 0)  ...
                                                               ^
  HINT:  No operator matches the given name and argument type(s). You might need to add explicit type casts.
  : SELECT  "orders".* FROM "orders" WHERE ("orders"."id" ILIKE 0)  ORDER BY "orders"."updated_at" DESC LIMIT 2 OFFSET 0
  </code></pre>
  
  <p>What might be the issue?</p>