Re: TOAST usage setting

From: "Zeugswetter Andreas ADI SD" <ZeugswetterA(at)spardat(dot)at>
To: "Bruce Momjian" <bruce(at)momjian(dot)us>, <pgsql-hackers(at)postgresql(dot)org>
Cc: "Gregory Stark" <stark(at)enterprisedb(dot)com>, "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Subject: Re: TOAST usage setting
Date: 2007-05-30 11:04:33
Message-ID: E1539E0ED7043848906A8FF995BDA579021B2AE2@m0143.s-mxs.net
Views: Raw Message | Whole Thread | Download mbox | Resend email
Thread:
Lists: pgsql-hackers


> I reran the tests with hashtext(), and created a SUMMARY.HTML chart:
>
> http://momjian.us/expire/TOAST/
>
> What you will see is that pushing TEXT to a TOAST column
> allows quick access to non-TOAST values and single-row TOAST
> values, but accessing all TOAST columns is slower than
> accessing them in the heap, by a factor of 3-18x.

Um, my understanding for this measurement would be to tweak
TOAST_TUPLE_THRESHOLD, and use a fixed TOAST_MAX_CHUNK_SIZE ?
Why would you want to increase the number of toast tuples required for
one column value ?

My expectation would be, that we want to allow a toast tuple to fill a
whole page (TOAST_TUPLES_PER_PAGE = 1),
but keep or reduce the threshold. Maybe we need other logic to find and
use free space for that, though (8.4 material).

Andreas

In response to

Responses

Browse pgsql-hackers by date

  From Date Subject
Next Message Hannes Eder 2007-05-30 11:56:24 Re: msvc, build and install with cygwin in the PATH
Previous Message Magnus Hagander 2007-05-30 10:28:28 Re: msvc, build and install with cygwin in the PATH