| From: | Robert Haas <robertmhaas(at)gmail(dot)com> |
|---|---|
| To: | Petr Jelinek <petr(at)2ndquadrant(dot)com> |
| Cc: | Dilip Kumar <dilipbalaut(at)gmail(dot)com>, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>, Andres Freund <andres(at)anarazel(dot)de>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Andres Freund <andres(at)2ndquadrant(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Relation extension scalability |
| Date: | 2016-03-11 21:29:39 |
| Message-ID: | CA+TgmoY0BqcYJLUuBkoFE9S_ztR=12FpXmPZ-p9WnFE8AQuT3w@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Thu, Mar 10, 2016 at 8:54 PM, Petr Jelinek <petr(at)2ndquadrant(dot)com> wrote:
> I am not talking about extension locks, the lock queue can be long because
> there is concurrent DDL for example and then once DDL finishes suddenly 100
> connections that tried to insert into table will try to get extension lock
> and this will add 2000 new pages when much fewer was actually needed. I
> guess that's fine as it's corner case and it's only 16MB even in such
> extreme case.
I don't really understand this part about concurrent DDL. If there
were concurrent DDL going on, presumably other backends would be
blocked on the relation lock, not the relation extension lock - and it
doesn't seem likely that you'd often have a huge pile-up of inserters
waiting on concurrent DDL. But I guess it could happen.
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
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