From: | Hannu Krosing <hannu(at)tm(dot)ee> |
---|---|
To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: Further open item (Was: Status of 7.2) |
Date: | 2001-11-23 09:58:19 |
Message-ID: | 3BFE1DBB.9090105@tm.ee |
Views: | Raw Message | Whole Thread | Download mbox | Resend email |
Thread: | |
Lists: | pgsql-hackers |
Tom Lane wrote:
>Hannu Krosing <hannu(at)tm(dot)ee> writes:
>
>>But could we not make it so that rollback will also reset xmax and cmax
>>to 0.
>>
>
>We never have done that and I don't see why we should start.
>(And no, I'm not sure that it'd be entirely safe; there are
>concurrency/atomicity issues involved, because we do not
>insist on getting exclusive lock to set the it's-dead-Jim
>flag bit.)
>
>We could make the user readout of xmax/cmax be zeroes if the flag
>bits show they are invalid.
>
If there is a cheap way to get a list of pending transactions, then we
could make them
read out as 0 if they are about to be deleted (ie xmax in
pending_transactions()) and
else show the value of the transaction that is about to delete them.
>But this really just begs the question
>of what use they are to users in the first place. I can't see any;
>and if we make them read as zeroes then they for sure won't have any.
>
I can see some use for xmax user-visible only while being deleted.
At least this would be more useful than themeaning
last-trx-that-was-about-to-delete.
Another way for getting equivalent functionality would be to make the
pending_transactions() function available to users.
---------------
Hannu
From | Date | Subject | |
---|---|---|---|
Next Message | Kovacs Zoltan | 2001-11-23 10:24:45 | hu.po |
Previous Message | Tatsuo Ishii | 2001-11-23 07:34:39 | Re: OCTET_LENGTH is wrong |