Matt Clark <matt(at)ymogen(dot)net> writes:
> Well, 74000/76000000 ~= 0.1%, way less than 1/26, so no surprise that an
> indexscan is better, and also no surprise that the planner can't know
> that I is such an uncommon initial char.
But it *can* know that, at least given adequate ANALYZE statistics.
I'm pretty convinced that the basic answer to Allen's problem is to
increase the histogram size. How large he needs to make it is not
clear --- obviously his data distribution is not uniform, but I don't
have a fix on how badly non-uniform.
regards, tom lane