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Re: SSI non-serializable UPDATE performance

From: Simon Riggs <simon(at)2ndQuadrant(dot)com>
To: Dan Ports <drkp(at)csail(dot)mit(dot)edu>
Cc: pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: SSI non-serializable UPDATE performance
Date: 2011-04-27 17:26:52
Message-ID: BANLkTi=DVO4MV1pa8==e2ka1Bgwg-vN+qw@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-hackers
On Mon, Apr 25, 2011 at 4:33 AM, Dan Ports <drkp(at)csail(dot)mit(dot)edu> wrote:
> On Sat, Apr 23, 2011 at 08:54:31AM -0500, Kevin Grittner wrote:
>> Even though this didn't show any difference in Dan's performance
>> tests, it seems like reasonable insurance against creating a new
>> bottleneck in very high concurrency situations.
>>
>> Dan, do you have a patch for this, or should I create one?
>
> Sure, patch is attached.


Reading the code, IIUC, we check for RW conflicts after each write but
only if the writer is running a serializable transaction.

Am I correct in thinking that there is zero impact of SSI if nobody is
running a serializable transaction?


-- 
 Simon Riggs                   http://www.2ndQuadrant.com/
 PostgreSQL Development, 24x7 Support, Training & Services

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