From: | Jan Wieck <JanWieck(at)Yahoo(dot)com> |
---|---|
To: | Greg Sabino Mullane <greg(at)turnstep(dot)com> |
Cc: | pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: Exposing the Xact commit order to the user |
Date: | 2010-05-25 19:58:14 |
Message-ID: | 4BFC2BD6.704@Yahoo.com |
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Thread: | |
Lists: | pgsql-hackers |
On 5/24/2010 9:30 AM, Greg Sabino Mullane wrote:
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: RIPEMD160
>
>
>> In light of the proposed purging scheme, how would it be able to distinguish
>> between those two cases (nothing there yet vs. was there but purged)?
>
>> There is a difference between an empty result set and an exception.
>
> No, I meant how will the *function* know, if a superuser and/or some
> background process can purge records at any time?
The data contains timestamps which are supposedly taken in commit order.
Checking the age of the last entry in the file should be simple enough
to determine if the segment matches the "max age" configuration (if
set). In the case of a superuser telling what to purge he would just
call a function with a serial number (telling the obsolete segments).
Jan
--
Anyone who trades liberty for security deserves neither
liberty nor security. -- Benjamin Franklin
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