From: | Josh Berkus <josh(at)agliodbs(dot)com> |
---|---|
To: | Robert Haas <robertmhaas(at)gmail(dot)com> |
Cc: | Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>, pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: Idea for getting rid of VACUUM FREEZE on cold pages |
Date: | 2010-05-26 21:01:24 |
Message-ID: | 4BFD8C24.1020606@agliodbs.com |
Views: | Raw Message | Whole Thread | Download mbox | Resend email |
Thread: | |
Lists: | pgsql-hackers |
> What if we drove it off of the PD_ALL_VISIBLE bit on the page itself,
> rather than the visibility map bit? It would be safe to clear the
> visibility map bit without touching the page, but if you clear the
> PD_ALL_VISIBLE bit on the page itself then you set all the hint bits
> and freeze all the tuples. In the case where the visibility map bit
> gets cleared but the page-level bit is still set, a future vacuum can
> notice and reset the visibility map bit. But whenever the visibility
> map bit is set, you know that the page-level bit MUST be set, so you
> needn't vacuum those pages, even for anti-wraparound: you know they'll
> be frozen when and if they ever get written again.
How does that get us out of reading and writing old pages, though? If
we're going to set a bit on them, we might as well freeze them.
--
-- Josh Berkus
PostgreSQL Experts Inc.
http://www.pgexperts.com
From | Date | Subject | |
---|---|---|---|
Next Message | alvherre | 2010-05-26 21:01:43 | Re: Show schema name on REINDEX DATABASE |
Previous Message | Heikki Linnakangas | 2010-05-26 20:52:35 | Re: Exposing the Xact commit order to the user |