Re: HOT patch - version 15

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 an open question is whether defragmentation should happen _only_
when we are trying to add something to the page and it doesn't fit.
Another open question is whether pruning should happen only when the
chain gets to a certain length.

The larger question is how are we going to get these answers?

--
  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. +