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Re: Re: patch submission: truncate trailing nulls from heap rows to reduce the size of the null bitmap [Review]

From: Simon Riggs <simon(at)2ndQuadrant(dot)com>
To: Amit Kapila <amit(dot)kapila(at)huawei(dot)com>
Cc: Kevin Grittner <kgrittn(at)mail(dot)com>, robertmhaas(at)gmail(dot)com, josh(at)agliodbs(dot)com, pgsql-hackers(at)postgresql(dot)org
Subject: Re: Re: patch submission: truncate trailing nulls from heap rows to reduce the size of the null bitmap [Review]
Date: 2013-01-09 12:14:34
Message-ID: CA+U5nMJgHY9=ZA88cH41bYaiH1DOcmF5SymYEe6+HrFEXCy_iw@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-hackers
On 9 January 2013 12:06, Amit Kapila <amit(dot)kapila(at)huawei(dot)com> wrote:
> On Wednesday, January 09, 2013 4:52 PM Simon Riggs wrote:
>> On 24 December 2012 16:57, Amit Kapila <amit(dot)kapila(at)huawei(dot)com> wrote:
>>
>> > Performance: Average of 3 runs of pgbench in tps
>> > 9.3devel  |  with trailing null patch
>> > ----------+--------------------------
>> > 578.9872  |   573.4980
>>
>> On balance, it would seem optimizing for this special case would
>> affect everybody negatively; not much, but enough. Which means we
>> should rekect this patch.
>>
>> Do you have a reason why a different view might be taken?
>
> I have tried to dig why this gap is coming. I have observed that there is
> very less change in normal path.
> I wanted to give it some more time to exactly find if something can be done
> to avoid performance dip in normal execution.
>
> Right now I am busy in certain other work. But definitely in coming week or
> so, I shall spare time to work on it again.

Perhaps. Not every idea produces useful outcomes. Even after your
excellent research, it appears we haven't made this work yet. It's a
shame. Should we invest more time? It's considered rude to advise
others how to spend their time, but let me say this: we simply don't
have enough time to do everything and we need to be selective,
prioritising our time on to the things that look to give the best
benefit.

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


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Subject: Re: Extra XLOG in Checkpoint for StandbySnapshot
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