Re: PATCH: adaptive ndistinct estimator v4 - Mailing list pgsql-hackers

From Josh Berkus
Subject Re: PATCH: adaptive ndistinct estimator v4
Date
Msg-id 55564A96.7040506@agliodbs.com
Whole thread Raw
In response to PATCH: adaptive ndistinct estimator v3 (WAS: Re: [PERFORM] Yet another abort-early plan disaster on 9.3)  (Tomas Vondra <tv@fuzzy.cz>)
Responses Re: PATCH: adaptive ndistinct estimator v4  (Robert Haas <robertmhaas@gmail.com>)
List pgsql-hackers
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



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