| From: | Noah Misch <noah(at)leadboat(dot)com> |
|---|---|
| To: | Pavel Stehule <pavel(dot)stehule(at)gmail(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 15:28:52 |
| Message-ID: | 20110208152852.GA31830@tornado.gateway.2wire.net |
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| Lists: | pgsql-hackers |
On Tue, Feb 08, 2011 at 08:00:42AM +0100, Pavel Stehule wrote:
> 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.
Robert spoke of doing it on usage (exec_eval_datum()) too, though.
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