| From: | Simon Riggs <simon(at)2ndquadrant(dot)com> |
|---|---|
| To: | Bruce Momjian <bruce(at)momjian(dot)us> |
| Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Heikki Linnakangas <heikki(at)enterprisedb(dot)com>, Florian Pflug <fgp(dot)phlo(dot)org(at)gmail(dot)com>, Pavan Deolasee <pavan(dot)deolasee(at)gmail(dot)com>, Gregory Stark <stark(at)enterprisedb(dot)com>, PostgreSQL-patches <pgsql-patches(at)postgresql(dot)org> |
| Subject: | Re: HOT patch - version 15 |
| Date: | 2007-09-09 12:25:44 |
| Message-ID: | 1189340744.4281.75.camel@ebony.site |
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| Lists: | pgsql-patches |
On Sun, 2007-09-09 at 07:55 -0400, Bruce Momjian wrote:
> Simon Riggs wrote:
> > On Sat, 2007-09-08 at 23:13 -0400, Bruce Momjian wrote:
> > > In summary, I feel we have the HOT mechanics down well, but the open
> > > issue is _when_ to activate each operation.
> >
> > That has been the only open issue for months. The interplay of behaviour
> > is where HOT succeeds and fails. Some behaviours sound like they will be
> > good, but aren't.
>
> Looking at the patch, it seems defragmentation is checked every time a
> heap page is pinned in heapam.c by calling heap_page_prune_defrag(). If
> page free space < 1.2 * average_tuple_size the page is defragmented. It
> would seem defragmentation is checked as much as possible. Seems
> pruning is also as aggressive as possible.
I think the factor should be 1.0. A Setting of 1.2 will lead to twice as
many defragmentation attempts when we have a fixed row length.
--
Simon Riggs
2ndQuadrant http://www.2ndQuadrant.com
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