From: | "Heikki Linnakangas" <heikki(at)enterprisedb(dot)com> |
---|---|
To: | "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | "Pavan Deolasee" <pavan(dot)deolasee(at)gmail(dot)com>, "Gavin M(dot) Roy" <gmr(at)myyearbook(dot)com>, "Alvaro Herrera" <alvherre(at)commandprompt(dot)com>, "PostgreSQL-development" <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: 8.3.0 Core with concurrent vacuum fulls |
Date: | 2008-03-05 15:44:15 |
Message-ID: | 47CEBFCF.5080108@enterprisedb.com |
Views: | Raw Message | Whole Thread | Download mbox | Resend email |
Thread: | |
Lists: | pgsql-hackers |
Tom Lane wrote:
> The reason the critical section is so large is that we're manipulating
> the contents of a shared buffer, and we don't want a failure to leave a
> partially-modified page in the buffer. We could fix that if we were to
> memcpy the page into local storage and do all the pruning work there.
> Then the critical section would only surround copying the page back to
> the buffer and writing the WAL record. Copying the page is a tad
> annoying but heap_page_prune is an expensive operation anyway, and
> I think we really are at too much risk of PANIC the way it's being done
> now. Has anyone got a better idea?
We could do the pruning in two phases: first figure out what to do
without modifyng anything, outside critical-section, and then actually
do it, inside critical section.
Looking at heap_page_prune, we already collect information of what we
did in the redirected/nowdead/nowunused arrays for WAL logging purposes.
We could use that, but we would also have to teach heap_prune_chain to
not step into tuples that we've already decided to remove.
--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com
From | Date | Subject | |
---|---|---|---|
Next Message | Tom Lane | 2008-03-05 15:45:58 | Re: 8.3.0 Core with concurrent vacuum fulls |
Previous Message | Gavin M. Roy | 2008-03-05 15:40:39 | Re: 8.3.0 Core with concurrent vacuum fulls |