Re: benchmarking the query planner

Gregory Stark <stark@enterprisedb.com> writes:
> For that matter, if we do consider sampling 5% of the table we may as well
> just go ahead and scan the whole table. It wouldn't take much longer and it
> would actually produce good estimates.

Yeah.  Anything over a small fraction of a percent is going to imply
fetching every page anyway, for typical row widths.  If you want ANALYZE
to be cheap then you simply don't get to have a trustworthy value of
ndistinct.

Perhaps a better plan is to try to de-emphasize use of ndistinct,
though I concede I have no idea how to do that.
        regards, tom lane