title: Estimating index creation time in oracle
body: <p>I have some tables in Oracle enviroment which I have found could benefit from new indexes.
  However, they are big tables, ranging from 1M registers to 300M registers, so I would first try to estimate how much time it would take for the index creation take place, so I would know at least the order of magnitude it would take (hours, days, weeks)?</p>
  
  <p>Is there some heuristics/oracle function/rule of thumb that could help me into solving this issue?</p>