Re: FILLFACTOR and increasing index

From: Leonardo Francalanci <m_lists(at)yahoo(dot)it>
To: Simon Riggs <simon(at)2ndQuadrant(dot)com>
Cc: Andrew Sullivan <ajs(at)crankycanuck(dot)ca>, pgsql-general <pgsql-general(at)postgresql(dot)org>
Subject: Re: FILLFACTOR and increasing index
Date: 2011-05-09 15:25:08
Message-ID: 105116.24690.qm@web29006.mail.ird.yahoo.com
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> It will be really useful to see some test results where you alter the
> fillfactor and report various measurables.

It's not that easy... stressing "only" the index insertion
speed won't be simple. I would have liked some "theory"...
The docs seem to imply there are some guidelines, it's
just that it's too cryptic:

"for heavily updated tables a smaller fillfactor is better
to minimize the need for page splits"

"heavily updated" -> does it mean tables that are inserted/updated
or only "updated"???

"leaf pages are filled to this percentage [...] when extending the index
at the right (adding new largest key values)."

Does it mean that since I will (almost) always add new largest key
values, I should have a big or small FILLFACTOR???

I know that theory is one thing and real testing another; but I can't
test everything; if there are some (proved?) guidelines I'd like to
use them (example: I'm not going to test that fillfactor in table creation
in my case won't make any difference in performance; I trust the
docs and the fact that "it makes sense").

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