title: variable width index oracle
body: <p>using oracle 11g.</p>
  
  <p>I'm looking for a feature which will allow me to define an index with variable width which depends on the occurrence rate of a given value. this is for non unique indexes with range scans.</p>
  
  <p>i.e.</p>
  
  <p>table T is </p>
  
  <p>column J,column K, column L, ...</p>
  
  <p>index I is </p>
  
  <p>non-unique index on T (J (, - if more than 1% -   K (, - if more than 10% -   L ) ))</p>
  
  <p>this way the index will be narrow for values with low occurrence rate (long tail) and wider for values with high occurrence rate.</p>
  
  <p>now when i select from the table using (J,K,L) it will use the index and get a narrow pretty much ordered result set always.</p>
  
  <p>any ideas? does such a thing exist?
  i thought of partitioning but it might be cumbersome. </p>
  
  <p>P.S. will also be OK with fixed numbers instead of percentages.</p>