What does ExtJS ComboBox triggerAction: "all” really do?

I tried to create a simple ComboBox:

var combo1 = new Ext.form.ComboBox({

  store: [1,2,3],

  renderTo: document.body

});

But written this way it acts strangely:

• When you first time pop open the dropdown, it offers three choices.
  


• You choose one.
  


• But when you after that try to change your selection, the dropdown only offers one choice - the one you previously selected.
  

I compared my code to the samples on Ext homepage and discovered that adding triggerAction: "all" solves my problem:

var combo2 = new Ext.form.ComboBox({

  triggerAction: "all",

  store: [1,2,3],

  renderTo: document.body

});

ExtJS documentation for triggerAction doesn't tell me a lot:

The action to execute when the trigger is clicked. Use 'all' to run the query specified by the allQuery config option (defaults to 'query')

I haven't specified the allQuery option. Actually, I don't want to perform a query to the server at all.

So what does this triggerAction really do?

And is setting it to "all" really what I should do when I just want a simple static combobox?

Source: Tips4all