title: Firebase realtime DB rule based on data.child do not work
body: <p>I like to retrieve the list of items only the ones its delete flag is false. but this setting does not work.</p>
  
  <pre class="lang-js prettyprint-override"><code>{
    &quot;rules&quot;: {
      &quot;items&quot;: {
        &quot;.read&quot;: &quot;data.child('isDelete').val() == false&quot;,
        &quot;$uid&quot;: {
          &quot;.write&quot;: &quot;auth != null &amp;&amp; !data.exists()&quot;
        }
      }
    }
  }
  </code></pre>
  <p>Here's a result from Rules playground request I tried.</p>
  <p>Request details</p>
  <pre class="lang-js prettyprint-override"><code>{
    &quot;auth&quot;: null,
    &quot;resource&quot;: {
      &quot;key&quot;: &quot;value&quot;
    },
    &quot;path&quot;: &quot;/items&quot;,
    &quot;method&quot;: &quot;get&quot;,
    &quot;time&quot;: &quot;2022-07-07T09:24:31.042Z&quot;
  }
  </code></pre>
  <p>Result details</p>
  <pre class="lang-js prettyprint-override"><code>Line 4 (/items)
  read: &quot;data.child('isDelete').val() == false&quot;
  </code></pre>
  <p>The data structure</p>
  <pre class="lang-js prettyprint-override"><code>items
  - 1xxxxxxxxxx
   title:&quot;title text 1&quot;
   createdAt:&quot;2022-06-05T04:21:57.322Z&quot;
   isDelete:false
  - 2xxxxxxxxxxxxx
   title:&quot;title text 2&quot;
   createdAt:&quot;2022-06-05T04:21:50.322Z&quot;
   isDelete:true
  </code></pre>
  <p>What is wrong?</p>