Quesiton on optimization ratio in DBD results

Hi,

When I ran DBD for incremental design, there were following two messages thrown as part of the optimization results. Query 4 is a simple single column select query on a view whereas Query 5 is a query which has three columns selected, of which one is as is column from, a second column using extract function on a timestamp column and the third column is simply count(1). What does Optimization ratio 1 mean? What query types does DBD fail  to optimize the query for? 

    Query optimization results...ent script...
         Query 1 optimization ratio or status is 1
         Query 4 optimization ratio or status is CANNOT BE OPTIMIZED DUE TO QUERY TYPE
         Query 5 optimization ratio or status is CANNOT BE OPTIMIZED DUE TO QUERY TYPE

Thanks, Kharvi