title: Reduction Factor of an Index Scanned Relation
body: <p>Say I have a relational schema as follows </p>
  
  <pre><code>Emp(eid: integer, did: integer, sal: integer, hobby: char(20))
  </code></pre>
  
  <p>It has <code>50000</code> distinct records, and a page can fit in <code>100</code> Tuples (which means there are <code>500</code> Pages).</p>
  
  <p>It has a clustered <code>B+</code> tree index on <code>(Emp.did)</code> of size <code>50</code> pages.</p>
  
  <p>If I were to do an Index Scan of EMP, and calculate the cost for it, I am confused as to what Reduction Factor should I utilize to calculate the cost of it? </p>
  
  <p>Should it be <code>1/50000</code> or <code>1/50</code>? </p>