title: What index should be created for low cardinality high updating columns in oracle?
body: <p>In Oracle 11g, say, I have a table <code>Task</code> which has a column <code>ProcessState</code>. The values of this column can be <code>Queued</code>, <code>Running</code> and <code>Complete</code> (can have couple more states in future). The table will have 50M+ data with 99.9% of rows having <code>Complete</code> as that column value. Only a few thousand rows will have value <code>Queued</code>/<code>Running</code>. </p>
  
  <p>I read that although <code>bitmap</code> index is good for low cardinality column, but that is used largely for static tables.</p>
  
  <p>So, what index can improve the query for <code>Queued</code>/<code>Running</code> tasks? <code>bitmap</code> or normal non-unique <code>b-tree</code> index?</p>
  
  <p>Also, what index can improve the query for a binary column (<code>NUMBER(1,0)</code> with just <code>yes</code>/<code>no</code> values) ?</p>
  
  <p>Disclaimer: I am an accidental dba.</p>