title: MongoDB command `compact` is not working
body: <p>I have a collection of documents in which I store an array of numbers. This collection is replenished with new documents about every 10 seconds. Every day I run a script which handles this arrays and leaves in documents only one number. After 3 month of data collecting I want to release disk space. Here is stat info of the collection from Robomongo:</p>
  <pre><code>{
      &quot;ns&quot; : &quot;orderbook&quot;,
      &quot;count&quot; : 5363208,
      &quot;size&quot; : 844457120,
      &quot;avgObjSize&quot; : 157,
      &quot;storageSize&quot; : 2795139072.0,
      &quot;capped&quot; : false,
      &quot;wiredTiger&quot; : {
          &quot;metadata&quot; : {
              &quot;formatVersion&quot; : 1
          }
      }
      &quot;nindexes&quot; : 2,
      &quot;totalIndexSize&quot; : 144482304,
      &quot;indexSizes&quot; : {
          &quot;_id_&quot; : 90615808,
          &quot;date_1&quot; : 53866496
      }
  }
  </code></pre>
  <p>As you can see the storageSize is much larger than the size. I expect that command <code>compact</code> will release disc space.</p>
  <p>What I do in mongo shell:</p>
  <pre><code>use trading
  db.runCommand({compact:'orderbook', force: true})
  </code></pre>
  <p>The answer is</p>
  <blockquote>
  <p>{ &quot;ok&quot; : 1 }</p>
  </blockquote>
  <p>Logs from /var/log/mongodb/mongod.log:</p>
  <blockquote>
  <p>2016-12-26T11:19:55.468+0300 I COMMAND  [conn7] compact trading.orderbook begin, options: paddingMode: NONE validateDocuments: 1</p>
  <p>2016-12-26T11:19:55.562+0300 I COMMAND  [conn7] compact trading.orderbook end</p>
  </blockquote>
  <p>Nothing happens. storageSize has the same value.</p>
  <p>Any ideas? What am I doing wrong?</p>