re: partition wise aggregate wrong rows cost

> We try fairly hard to ensure that the row count estimate for a given relation
> does not vary across paths, so I concur with the OP that this is a bug.  Having
> said that, I'm not sure that the consequences are significant.  As you say, the
> estimates seem to get a lot closer as soon as the table has some statistics.
> (But nonetheless, they are not identical, so it's still a bug.)

Yes, the estimates seem to get a lot closer as soon as the table has some statistics.

> I'm not sure that the consequences are significant.
At least it doesn't make any difference to me for now.
I noticed this problem while testing aggregation.
It looks a little weird, so I emailed.

Thanks every one.