| From: | Dimitri Fontaine <dfontaine(at)hi-media(dot)com> |
|---|---|
| To: | Bruce Momjian <bruce(at)momjian(dot)us> |
| Cc: | Robert Haas <robertmhaas(at)gmail(dot)com>, Greg Stark <gsstark(at)mit(dot)edu>, decibel <decibel(at)decibel(dot)org>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Simon Riggs <simon(at)2ndquadrant(dot)com>, Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>, Aidan Van Dyk <aidan(at)highrise(dot)ca>, Alvaro Herrera <alvherre(at)commandprompt(dot)com>, Pg Hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Page-level version upgrade |
| Date: | 2009-12-02 11:26:39 |
| Message-ID: | 87fx7t39cg.fsf@hi-media-techno.com |
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| Lists: | pgsql-hackers |
Hi,
As we're talking about crazy ideas...
Bruce Momjian <bruce(at)momjian(dot)us> writes:
> Well, yea, the idea would be that the 8.5 server would either convert
> the page to the new format on read (assuming there is enough free space,
> perhaps requiring a pre-upgrade script), or have the server write the
> page in the old 8.4 format and not do CRC checks on the page. My guess
> is the former.
We already have had demand for read only tables (some on-disk format
optimisation would then be possible). What about having page level
read-only restriction, thus allowing the newer server version to operate
in read-only mode on the older server version pages, and convert on
write by allocating whole new page(s)?
Then we go even crazier, with a special recovery mode on the new version
able to read older version WAL format, producing older version
pages. That sounds like code maintenance hell, but would allow for a
$new WAL standby to restore from a $old wal steam, and be read
only. Then you sitchover to the slave and it goes out of recovery and
creates new pages on writes.
How about going this crazy?
Regards,
--
dim
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