Re: Temporary tables under hot standby
От | Robert Haas |
---|---|
Тема | Re: Temporary tables under hot standby |
Дата | |
Msg-id | CA+TgmoZZEvu+MKs4dF2Q9Rz+u_dU_P2p9-GQW10CTQ3rKyQrGQ@mail.gmail.com обсуждение исходный текст |
Ответ на | Re: Temporary tables under hot standby (Simon Riggs <simon@2ndQuadrant.com>) |
Ответы |
Re: Temporary tables under hot standby
(Simon Riggs <simon@2ndQuadrant.com>)
Re: Temporary tables under hot standby (Merlin Moncure <mmoncure@gmail.com>) |
Список | pgsql-hackers |
On Wed, Apr 25, 2012 at 12:30 PM, Simon Riggs <simon@2ndquadrant.com> wrote: > On Wed, Apr 25, 2012 at 5:19 PM, Robert Haas <robertmhaas@gmail.com> wrote: > >> Oh, we're talking about different things, and I'm slightly confused. >> >> Yes, we need to support ANALYZE; what we might not need to support, at >> least initially, is every user of a global temp table having their own >> SEPARATE copy of the table statistics. > > Yes, we are. Global Temp Tables won't solve the "Works on HS" problem, > so we'd better decide fairly quickly which use case we are addressing, > and why. ISTM Global Temp Tables is more an Oracle compatibility issue > than a problem PostgreSQL users have. > > ...I have zero basis for deciding whether what you say about Global > Temp Tables is useful or not. Well, Noah presented a pretty good outline of how to make global temp tables work under Hot Standby. As Noah already said, making regular temporary tables work under Hot Standby is far more difficult. I think he's right. I'd rather see us get global temp tables working under HS than insist we have to have regular temp tables working under HS and ultimately end up with nothing. Even getting global temp tables working under HS is probably going to require an entire development cycle, maybe two. So raising the bar still higher seems rather self-defeating to me. Half a loaf is better than none. In the interest of full disclosure, I freely admit that global temporary tables would also be a neat Oracle compatibility feature, and I do work for a company that sells Oracle compatibility products based on PostgreSQL, so there are surely some reasons for me to like that, but AFAICT they aren't all *that* heavily used by most Oracle users either, which is why I haven't been able to justify doing this project before now. The important point here as I see it is that tables of any flavor require catalog entries, and creating and destroying catalog entries on a standby server does not seem tractable, so if we want to have writable tables of any flavor on Hot Standby sometime in the next year or two, we should pick a design that doesn't require that. What Noah has proposed seems to me to be by far the simplest way of making that happen, so I think his design is spot-on. -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company
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