"Joshua D. Drake" <jd(at)commandprompt(dot)com> writes:
> Tom Lane wrote:
>> That statement seems perfectly accurate to me.
> Considering an index of a,b if I search for b I would expect that the
> planner could use the index.
It can. Whether it will think that's a good idea is another question
entirely, and one that seems a bit beyond the scope of the discussion
you're mentioning.
Try forcing the issue with enable_seqscan, and see what sort of
estimated and actual costs you get ...
regards, tom lane