index selection by query planner

Hi,

 

I have a table with two indices on the same column, one of which is a partial index. I would like the query planner to use the partial index whenever the query condition lies in the range of the partial index as it would yield better performance. Is there any way to enforce the ordering for the indices? How does the query planner decide which index to use when a particular query is fired?  'Explain Analyze' showed the total index being used in a situation that could be fulfiled by the partial index.

 

Thanks,

Rohit