Re: PATCH: adaptive ndistinct estimator v4

On Fri, May 15, 2015 at 3:35 PM, Josh Berkus <josh(at)agliodbs(dot)com> wrote:
> 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.

This is clearly 9.6 material at this point, and has been for a while.
The patch - at least the last version I looked at - didn't store
anything different in pg_statistic. It just logged what it would have
stored. So testing is good, but there's not a question of pushing
this into 9.5.

--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company