Jeremy Harris <jgh(at)wizmail(dot)org> writes:
> On 22/01/14 03:53, Tom Lane wrote:
>> Jon Nelson <jnelson+pgsql(at)jamponi(dot)net> writes:
>>> - in createplan.c, eliding duplicate tuples is enabled if we are
>>> creating a unique plan which involves sorting first
>> [ raised eyebrow ... ] And what happens if the planner drops the
>> unique step and then the sort doesn't actually go to disk?
> I don't think Jon was suggesting that the planner drop the unique step.
Hm, OK, maybe I misread what he said there. Still, if we've told
tuplesort to remove duplicates, why shouldn't we expect it to have
done the job? Passing the data through a useless Unique step is
not especially cheap.
regards, tom lane