| From: | Kevin Grittner <kgrittn(at)gmail(dot)com> |
|---|---|
| To: | Andres Freund <andres(at)anarazel(dot)de> |
| Cc: | Ants Aasma <ants(dot)aasma(at)eesti(dot)ee>, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>, Noah Misch <noah(at)leadboat(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, Kevin Grittner <kgrittn(at)postgresql(dot)org>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org>, "pgsql-committers(at)postgresql(dot)org" <pgsql-committers(at)postgresql(dot)org> |
| Subject: | Re: [HACKERS] Re: pgsql: Avoid extra locks in GetSnapshotData if old_snapshot_threshold < |
| Date: | 2016-05-27 15:18:28 |
| Message-ID: | CACjxUsNQeGMTrMAQjHXRAvdUYDe1nYhA3une0xk_NoMNr+JH1Q@mail.gmail.com |
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| Lists: | pgsql-committers pgsql-hackers |
On Fri, May 27, 2016 at 9:58 AM, Kevin Grittner <kgrittn(at)gmail(dot)com> wrote:
> On Tue, May 24, 2016 at 4:56 PM, Andres Freund <andres(at)anarazel(dot)de> wrote:
>> If an old session with >= repeatable read accesses a clustered
>> table (after the cluster committed), they'll now not see any
>> errors, because all the LSNs look new.
>
> Again, it is new LSNs that trigger errors; if the page has not been
> written recently the LSN is old and there is no error. I think you
> may be seeing problems based on getting the basics of this
> backwards.
I am reviewing the suggestion of a possible bug now, and will make
it my top priority until resolved. By the end of 1 June I will
either have committed a fix or posted an explanation of why the
concern is mistaken, with test results to demonstrate correct
behavior.
--
Kevin Grittner
EDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
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