title: warning: use server-side selectize for massively improved performance in RShiny
body: <p>In an RShiny app, I am receiving the warning message <code>Warning message: The select input &quot;the_input_id&quot; contains a large number of options; consider using server-side selectize for massively improved performance. See the Details section of the ?selectizeInput help topic.</code></p>
  <p>I have a named vector <strong>namelist</strong> of length == 3000 that is used for the dropdown choices. I've tried the following two things to get rid of this warning:</p>
  <p><strong>ui</strong></p>
  <pre><code>selectizeInput(
    inputId = 'the_input_id', label = 'Player 1 Search:', choices = namelist, selected = NULL,
    options = list(placeholder = 'Please select an option below', onInitialize = I('function() { this.setValue(&quot;&quot;); }'))
  )
  
  uiOutput(outputId = 'this_id')
  </code></pre>
  <p><strong>server</strong></p>
  <pre><code>updateSelectizeInput(session = session, inputId = 'the_input_id', label = 'Player 1 Search:', choices = namelist, server = TRUE,
                      options = list(placeholder = 'Please select an option below', onInitialize = I('function() { this.setValue(&quot;&quot;); }')),
                             selected = &quot;&quot;
                             )
  
  output$this_id&lt;-renderUI ({
      selectizeInput(inputId = 'this_id', &quot;Player 2 Search:&quot;, namelist,
                     options = list(
                       placeholder = 'Please select an option below',
                       onInitialize = I('function() { this.setValue(&quot;&quot;); }')
                     ))
  })
  </code></pre>
  <p>The approach for <strong>the_input_id</strong> is to use a selectizeInput() in the UI, and an updateSelectizeInput() in the server (I thought this was the correct approach for server-side selectize). The approach for <strong>this_id</strong> is to use an uiOutput() in the UI, and a renderUI + selectizeInput on the server. Both of these approaches give the same warning message that I posted above. How can I resolve the issue / to get rid of this warning message.</p>