title: How can I estimate the size of an Oracle index?
body: <p>I'm considering adding an index to an Oracle table, but I'd like to first estimate the size of the index after it has been built (I don't need a precise size - just an estimate.)</p>
  
  <p>Supposing I have access to all of the meta-data about the table (number of rows, columns, column data types, etc) that I can execute any arbitrary Oracle SQL query to get additional data about the current state of the table, and I know what I would want the index definition to be, how can I estimate this size?</p>