From: | Heikki Linnakangas <heikki(at)enterprisedb(dot)com> |
---|---|
To: | Simon Riggs <simon(at)2ndquadrant(dot)com> |
Cc: | Alvaro Herrera <alvherre(at)commandprompt(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: Free Space Map thoughts |
Date: | 2007-11-09 09:45:36 |
Message-ID: | 47342C40.5090201@enterprisedb.com |
Views: | Raw Message | Whole Thread | Download mbox | Resend email |
Thread: | |
Lists: | pgsql-hackers |
Simon Riggs wrote:
> On Thu, 2007-11-08 at 21:50 -0300, Alvaro Herrera wrote:
>> Simon Riggs wrote:
>>
>>> Presumably we would not store an FSM for small tables? On the basis that
>>> the purpose of the FSM is to save on pointless I/O there must be a size
>>> of table below which an FSM is just overhead.
>> Hmm, do you mean that we would open and verify every page of a small
>> relation until we find one with free space? That doesn't sound very
>> good.
>
> I was trying to guess at Heikki's reason for saying the FSM should be in
> a separate file. If we have one extra file per table that seems like a
> huge number of additional files, with space and fsync implications.
You need the same amount of space either way. Well, I guess additional
files consume some space in the filesystem directory structures. I doubt
that matters.
You do need more fsyncs, and more overhead when creating/dropping
relations, to create/unlink the FSM files. I don't know how significant
that is.
--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com
From | Date | Subject | |
---|---|---|---|
Next Message | Simon Riggs | 2007-11-09 09:50:00 | Re: Free Space Map thoughts |
Previous Message | Heikki Linnakangas | 2007-11-09 09:39:40 | Re: Free Space Map thoughts |