Re: same query different execution plan (hash join vs. semi-hash join)

"Huang, Suya" <Suya.Huang@au.experian.com> writes:
> Thank you Tom. But the time spent on scanning table test1 is less than 1 second (91.738 compares to 87.869), so I
guessthis shouldn't be the issue? 

No, the point is that the bad rowcount estimate (and, possibly, lack of
stats about join column contents) causes the planner to pick a join method
that's not ideal for this query.

            regards, tom lane