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

From: Robert Haas <robertmhaas(at)gmail(dot)com>
To: Josh Berkus <josh(at)agliodbs(dot)com>
Cc: pgsql-hackers(at)postgresql(dot)org
Subject: Re: patch submission: truncate trailing nulls from heap rows to reduce the size of the null bitmap
Date: 2012-06-26 21:04:42
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Lists: pgsql-hackers
On Wed, May 2, 2012 at 9:01 PM, Josh Berkus <josh(at)agliodbs(dot)com> wrote:
> On 5/2/12 10:20 AM, Jameison Martin wrote:
>> Attached are the following as per various requests:
>>       * test_results.txt: the performance benchmarking results,
>>       * the performance benchmarking code, with a few additional scenarios as per various requests
>>       * hardinfo_report.txt: some information about the hardware and OS of the system on which the benchmarks were run, and
>>       * postgresql.conf: the postgresql.conf used when running benchmarks. Note that the changes made to the vanilla postgresql.conf can be identified by looking for the string 'jamie' in the file I attached (there aren't that many)
> Nice, thanks.  I'll try some of my own tests when I get a chance; I have
> a really good use-case for this optimization.


The CommitFest application lists you as the reviewer for this patch.
Are you (I hope) planning to review it?

I see you posted up a follow-up email asking Tom what he had in mind.
Personally, I don't think this needs incredibly complicated testing.
I think you should just test a workload involving inserting and/or
updating rows with lots of trailing NULL columns, and then another
workload with a table of similar width that... doesn't.  If we can't
find a regression - or, better, we find a win in one or both cases -
then I think we're done here.

Robert Haas
The Enterprise PostgreSQL Company

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