| From: | Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com> |
|---|---|
| To: | Noah Misch <noah(at)leadboat(dot)com> |
| Cc: | Robert Haas <robertmhaas(at)gmail(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(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: | 2011-02-08 07:00:42 |
| Message-ID: | AANLkTi=JiYqAmxP5cpe7og3KZQgCes0rt+vY2PH2rPD1@mail.gmail.com |
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| Lists: | pgsql-hackers |
2011/2/8 Noah Misch <noah(at)leadboat(dot)com>:
> On Mon, Feb 07, 2011 at 11:16:18PM -0500, Robert Haas wrote:
>> So
>> can we just get rid of should_be_detoasted, and have exec_eval_datum()
>> or its callers instead test:
>>
>> !var->isnull && var->datatype->typbyval && var->datatype->typlen == -1
>> && VARATT_IS_EXTENDED(var->value)
>
> FWIW, this is what I meant by option 2 in my summary.
>
>> I haven't tested this, but it's not clear that'd be measurably slower
>> than checking a single Boolean.
>
> Pavel benchmarked this or something close, measuring a performance loss:
> http://archives.postgresql.org/message-id/AANLkTikDHekc9r38w2ttzoMDr8vDaVAnr3LhqfJkEuL9@mail.gmail.com
I tested this in situation when Datum is detoasted on usage, not in
assignment. So impact will be less.
Regards
Pavel Stehule
>
> Tom also expressed concern over performance:
> http://archives.postgresql.org/message-id/24266.1295462892@sss.pgh.pa.us
>
> Not sure what's next.
>
> nm
>
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