Re: Re: [COMMITTERS] pgsql: Avoid extra locks in GetSnapshotData if old_snapshot_threshold <

From: Andres Freund <andres(at)anarazel(dot)de>
To: Robert Haas <robertmhaas(at)gmail(dot)com>
Cc: Kevin Grittner <kgrittn(at)gmail(dot)com>, 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>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Re: [COMMITTERS] pgsql: Avoid extra locks in GetSnapshotData if old_snapshot_threshold <
Date: 2016-05-02 14:21:21
Message-ID: 20160502142121.fn2y3walpebprccn@alap3.anarazel.de
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On 2016-05-02 09:03:19 -0400, Robert Haas wrote:
> On Fri, Apr 29, 2016 at 6:08 PM, Kevin Grittner <kgrittn(at)gmail(dot)com> wrote:
> > Now to continue with the performance benchmarks. I'm pretty sure
> > we've fixed the problems when the feature is disabled
> > (old_snapshot_threshold = -1), and there are several suggestions
> > for improving performance while it is on that need to be compared
> > and benchmarked.
>
> If anyone thinks that the issue with the feature disabled is NOT
> fixed, please speak up! I'm moving the corresponding open item to
> CLOSE_WAIT status, meaning that it will be closed if nobody shows up
> to say that there is still an issue.

Well, I don't agree that the feature is in a releaseable state. The
datastructure is pretty much non-scalable, and maintained on the wrong
side (every read, instead of once in writing writing xacts). There's no
proposal actually addressing the scalability issues.

Andres

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