Re: PATCH: adaptive ndistinct estimator v4

On 05/15/2015 11:30 AM, Robert Haas wrote:
> Once we enter beta (or even feature freeze), it's too late to whack
> around the algorithm heavily. We're pretty much committed to
> releasing and supporting whatever we have got at that point. I guess
> we could revert it if it doesn't work out, but that's about the only
> option at that point. We have more flexibility during the main part
> of the development cycle. But your point is certainly valid and I
> don't mean to dispute it.

I will finally have a customer workload available to test this on this
weekend. That's been rather delayed by the availability of customer
hardware,because I'm not allowed to copy out the database. However,
this is a database which suffers from multiple ndistinct estimation
issues in production, so I should be able to get a set of stats back by
Monday which would show how much of a general improvement it is.

I realize that's after the deadline, but there wasn't much I could do
about it. I've tried to simulate the kind of estimation issues I've
seen, but they don't simulate well.

--
Josh Berkus
PostgreSQL Experts Inc.
http://pgexperts.com