John Siracusa <siracusa(at)mindspring(dot)com> writes:
> I think the key is to get the planner to correctly ballpark the number of
> rows in the date range.
I thought it was. What you showed was
-> Index Scan using mytable_date_idx on mytable (cost=0.00..3071.70 rows=52155 width=23) (actual time=2.610..1688.111 rows=49679 loops=1)
which seemed plenty close enough to me.
regards, tom lane