Re: Exposing the Xact commit order to the user

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
Views: Raw Message | Whole Thread | Download mbox | Resend email
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

In response to

Responses

Browse pgsql-hackers by date

  From Date Subject
Next Message Tom Lane 2010-05-25 20:06:49 mergejoin null handling (was Re: [PERFORM] merge join killing performance)
Previous Message Kevin Grittner 2010-05-25 19:57:29 Re: Exposing the Xact commit order to the user