Horton

Re: Re: patch: fix performance problems with repated decomprimation of varlena values in plpgsql

Noah Misch <noah@leadboat.com>

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From: Noah Misch <noah@leadboat.com>
To: Robert Haas <robertmhaas@gmail.com>
Cc: Pavel Stehule <pavel.stehule@gmail.com>, Tom Lane <tgl@sss.pgh.pa.us>, Heikki Linnakangas <heikki.linnakangas@enterprisedb.com>, Kevin Grittner <Kevin.Grittner@wicourts.gov>, PostgreSQL Hackers <pgsql-hackers@postgresql.org>
Date: 2011-02-08T04:52:01Z
Lists: pgsql-hackers 
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

Tom also expressed concern over performance:
http://archives.postgresql.org/message-id/24266.1295462892@sss.pgh.pa.us

Not sure what's next.

nm