title: Pandas HDFStore of MultiIndex DataFrames: how to efficiently get all indexes
body: <p>In Pandas, is there a way to efficiently pull out all the MultiIndex indexes present in an HDFStore in table format?</p>
  
  <p>I can <code>select()</code> efficiently using <code>where=</code>, but I want all indexes, and none of the columns.  I can also <code>select()</code> using <code>iterator=True</code> to save RAM, but that still means reading pretty much all the table from disk, so it's still slow.</p>
  
  <p>I have been hunting in the store.root..table.* stuff, hoping that I can get a list of index values.  Am I on the right track?</p>
  
  <p>Plan B would be to keep a shorter MultiIndex DataFrame that just contains empty DataFrames appended every time I append the main one.  I can retrieve that and get the index much more cheaply than the main one.  Inelegant though.</p>