From: | Fujii Masao <masao(dot)fujii(at)gmail(dot)com> |
---|---|
To: | Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com> |
Cc: | Erik Rijkers <er(at)xs4all(dot)nl>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: Streaming replication and pg_xlogfile_name() |
Date: | 2010-03-02 13:52:16 |
Message-ID: | 3f0b79eb1003020552q3135bb0ey616dae796f00ab87@mail.gmail.com |
Views: | Raw Message | Whole Thread | Download mbox | Resend email |
Thread: | |
Lists: | pgsql-hackers |
On Tue, Mar 2, 2010 at 8:54 PM, Heikki Linnakangas
<heikki(dot)linnakangas(at)enterprisedb(dot)com> wrote:
> This still suffers from ambiguity around a shutdown checkpoint that
> changes the TLI. On the page the shutdown checkpoint is on, what is the
> TLI in the page header? The TLI before the checkpoint record, I presume.
> Now consider a record on the same page after the checkpoint record. It's
> on the new timeline, but pg_last_xlog_replay_location() will return the
> old TLI, because that's on the page header.
Oh, I see. You are right.
> It's not clear what it should return, a TLI corresponding the filename
> of the WAL segment the record was replayed from, so that you can use
> pg_xlogfile_name() to find out the filename of the WAL segment being
> replayed, or the accurate TLI of the record being replayed. I'm leaning
> towards the latter, it feels more correct and accurate, but you could
> argue for the former too. In any case, it needs to be well-defined.
I agree with you that the latter is more correct and accurate. The simple
fix is updating the lastPageTLI with the CheckPoint->ThisTimeLineID when
replaying the shutdown checkpoint record. Though we might need to use new
variable to keep the last applied timeline instead of the lastPageTLI.
Regards,
--
Fujii Masao
NIPPON TELEGRAPH AND TELEPHONE CORPORATION
NTT Open Source Software Center
From | Date | Subject | |
---|---|---|---|
Next Message | Theo Schlossnagle | 2010-03-02 14:37:12 | Re: double and numeric conversion |
Previous Message | Greg Smith | 2010-03-02 13:36:56 | Re: building postgres-A4.tex-pdf crushed |