Re: Logical to physical page mapping

From: Bruce Momjian <bruce(at)momjian(dot)us>
To: Robert Haas <robertmhaas(at)gmail(dot)com>
Cc: Jan Wieck <JanWieck(at)yahoo(dot)com>, PostgreSQL Development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Logical to physical page mapping
Date: 2012-11-06 03:11:56
Message-ID: 20121106031156.GL19099@momjian.us
Views: Raw Message | Whole Thread | Download mbox | Resend email
Thread:
Lists: pgsql-hackers

On Mon, Oct 29, 2012 at 07:05:39AM -0400, Robert Haas wrote:
> Yet another idea we've tossed around is to make only vacuum records
> include FPWs, and have the more common heap insert/update/delete
> operations include enough information that they can still be applied
> correctly even if the page has been "torn" by the previous replay of
> such a record. This would involve modifying the recovery algorithm so
> that, until consistency is reached, we replay all records, regardless
> of LSN, which would cost some extra I/O, but maybe not too much to
> live with? It would also require that, for example, a heap-insert
> record mention the line pointer index used for the insertion;
> currently, we count on the previous state of the page to tell us that.
> For checkpoint cycles of reasonable length, the cost of storing the
> line pointer in every WAL record seems like it'll be less than the
> cost needing to write an FPI for the page once per checkpoint cycle,
> but this isn't certain to be the case for all workloads.

This last idea has the most promise for me. Vacuum is far less common
than row modification writes.

--
Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us
EnterpriseDB http://enterprisedb.com

+ It's impossible for everything to be true. +

In response to

Browse pgsql-hackers by date

  From Date Subject
Next Message Karl O. Pinc 2012-11-06 03:41:13 Re: Doc patch, distinguish sections with an empty row in error code table
Previous Message Andrew Dunstan 2012-11-06 02:37:30 Re: Pg_upgrade speed for many tables