Re: demystifying nested loop vs. merge join query plan choice

Sandeep Gupta <gupta.sandeep@gmail.com> writes:
> details regarding buffer usage:
> [ 100% buffer hit rate ]

Your database is evidently fully cached in memory.  If that's the
operating mode you expect, you need to change the planner's cost
parameters, in particular reduce random_page_cost to equal seq_page_cost.
There is plenty of material about this on the PG wiki or in the
pgsql-performance archives.

            regards, tom lane