| From: | Robert Haas <robertmhaas(at)gmail(dot)com> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | Michael Paquier <michael(dot)paquier(at)gmail(dot)com>, Kyotaro HORIGUCHI <horiguchi(dot)kyotaro(at)lab(dot)ntt(dot)co(dot)jp>, Sawada Masahiko <sawada(dot)mshk(at)gmail(dot)com>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: [HACKERS] More stats about skipped vacuums |
| Date: | 2017-11-26 20:05:27 |
| Message-ID: | CA+TgmoZH9LFhxX9r0hqrMN7eBySNabb5jkV4H9hcxyAcj2gnkA@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Sat, Nov 25, 2017 at 12:09 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Robert Haas <robertmhaas(at)gmail(dot)com> writes:
>> Of course, the other obvious question is whether we really need a
>> consistent snapshot, because that's bound to be pretty expensive even
>> if you eliminate the I/O cost. Taking a consistent snapshot across
>> all 100,000 tables in the database even if we're only ever going to
>> access 5 of those tables doesn't seem like a good or scalable design.
>
> Mumble. It's a property I'm pretty hesitant to give up, especially
> since the stats views have worked like that since day one. It's
> inevitable that weakening that guarantee would break peoples' queries,
> probably subtly.
You mean, queries against the stats views, or queries in general? If
the latter, by what mechanism would the breakage happen?
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
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