| From: | Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com> |
|---|---|
| To: | Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com> |
| Cc: | Noah Misch <noah(at)leadboat(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Kevin Grittner <Kevin(dot)Grittner(at)wicourts(dot)gov>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Re: patch: fix performance problems with repated decomprimation of varlena values in plpgsql |
| Date: | 2011-01-25 07:04:45 |
| Message-ID: | 4D3E760D.9010907@enterprisedb.com |
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| Lists: | pgsql-hackers |
On 25.01.2011 06:29, Pavel Stehule wrote:
> 2011/1/25 Noah Misch<noah(at)leadboat(dot)com>:
>> On Sat, Jan 22, 2011 at 11:32:02AM +0100, Pavel Stehule wrote:
>>> because I am not sure so any complex solution can be done to deadline
>>> for 9.1, I created a patch that is based on Tom ideas - just
>>> explicitly detoast function parameters.
>>
>> I can confirm that, for your original test case, this yields performance
>> comparable to that of your original patch.
>
> I know it :(. I am thinking, so detoasting on usage is better, but I
> am don't know more about Tom or Rober's plans.
Detoasting on first usage, ie. exec_eval_datum(), seems the best to me.
Compared to detoasting on assignment, it avoids the performance
regression if the value is never used, and I don't think checking if the
value is toasted at every exec_eval_datum() call adds too much overhead.
--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com
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