| From: | Robert Haas <robertmhaas(at)gmail(dot)com> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>, Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>, Noah Misch <noah(at)leadboat(dot)com>, 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 15:33:35 |
| Message-ID: | AANLkTik1Y1vc3QoW0mnA-fHbnL11p7hWAsx4cKa5oPkq@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Tue, Jan 25, 2011 at 10:03 AM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com> writes:
>> 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.
>
> The arguments that were made against this were about maintenance costs
> and code footprint. Claims about performance are not really relevant,
> especially when they're entirely unsupported by evidence.
How much evidence do you need to the effect that detoasting a value
that's never used will hurt performance?
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
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