Re: TOASTing smaller things - Mailing list pgsql-hackers

From Bruce Momjian
Subject Re: TOASTing smaller things
Date
Msg-id 200703212012.l2LKClX14319@momjian.us
Whole thread Raw
In response to Re: TOASTing smaller things  (Jan Wieck <JanWieck@Yahoo.com>)
Responses Re: TOASTing smaller things  ("Luke Lonergan" <llonergan@greenplum.com>)
List pgsql-hackers
Is this a TODO?

---------------------------------------------------------------------------

Jan Wieck wrote:
> On 3/21/2007 2:05 PM, Tom Lane wrote:
> > Chris Browne <cbbrowne@acm.org> writes:
> >> #define TOAST_DENOMINATOR 17  
> >>    /* Use this as the divisor; current default behaviour falls from TOAST_DENOMINATOR = 4 */
> > 
> >> #define TOAST_TUPLE_THRESHOLD^I\
> >> ^IMAXALIGN_DOWN((BLCKSZ - \
> >> ^I^I^I^I   MAXALIGN(sizeof(PageHeaderData) + 3 * sizeof(ItemIdData))) \
> >> ^I^I^I^I  / TOAST_DENOMINATOR)
> > 
> > Given that you are quoting code that was demonstrably broken since the
> > original coding of TOAST up till a month or two back, "it passes
> > regression" is not adequate proof of "it's right".  In fact I think
> > it's not right; you have not got the roundoff condition straight.
> > 
> >> 4.  A different mechanism would be to add a fifth storage column
> >> strategy (the present four are PLAIN, EXTENDED, EXTERNAL, MAIN), let's
> >> say, TOAST.
> 
> FORCE_COMPRESSION, FORCE_EXTERNAL and FORCE_EXTERNAL_UNCOMPRESSED.
> 
> > 
> > Anything along this line would require invoking the toaster on every
> > single tuple, since we'd always have to crawl through all the columns
> > to see if toasting was supposed to happen.  No thanks.
> 
> Not necessarily. A flag in Relation telling if the table has any column 
> marked like that could be set while constructing the relcache entry.
> 
> > 
> >> Which of these sounds preferable?
> > 
> > It's a bit late in the cycle to be proposing any of these for 8.3.
> 
> Certainly.
> 
> 
> Jan
> 
> -- 
> #======================================================================#
> # It's easier to get forgiveness for being wrong than for being right. #
> # Let's break this rule - forgive me.                                  #
> #================================================== JanWieck@Yahoo.com #
> 
> ---------------------------(end of broadcast)---------------------------
> TIP 2: Don't 'kill -9' the postmaster

--  Bruce Momjian  <bruce@momjian.us>          http://momjian.us EnterpriseDB
http://www.enterprisedb.com
 + If your life is a hard drive, Christ can be your backup. +


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