Re: Searching for the cause of a bad plan

Simon Riggs <simon@2ndquadrant.com> writes:
> On Fri, 2007-09-21 at 12:08 -0400, Tom Lane wrote:
>> The reason you get a bad plan is that this rowcount estimate is so far
>> off:

> That's true, but its not relevant,

Yes it is --- the reason it wants to use a hashjoin instead of a
nestloop is exactly that it thinks the loop would iterate too many
times.  (Ten is already too many in this case --- if it had estimated
five rows out of the join, it'd have gone with the nestloop, since
the cost estimate difference at the top level is less than 2x.)

            regards, tom lane