From: | "Zeugswetter Andreas ADI SD" <ZeugswetterA(at)spardat(dot)at> |
---|---|
To: | "Galy Lee" <lee(dot)galy(at)oss(dot)ntt(dot)co(dot)jp>, "Simon Riggs" <simon(at)2ndquadrant(dot)com> |
Cc: | "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us>, "Jim C(dot) Nasby" <jim(at)nasby(dot)net>, <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: Resumable vacuum proposal and design overview |
Date: | 2007-02-28 10:34:14 |
Message-ID: | E1539E0ED7043848906A8FF995BDA57901CAFD36@m0143.s-mxs.net |
Views: | Raw Message | Whole Thread | Download mbox | Resend email |
Thread: | |
Lists: | pgsql-hackers |
> > You haven't explained how saving the dead-tuple-list could be done
in
> > a safe mannner and it seems risky to me.
>
> The files are placed in a new directory $PGDATA/pg_vacuum
> with the name: spcNode.dbNode.relNode for each relations
> which have been interrupted during vacuum.
>
> It has the format likes:
>
> 1. VacStateFileHeader
> 2. VacStateData
> 3. Dead Tuple list
> 4. CRC32
>
> The files are removed
> - when original physical heap files are removed,
> - when vacuum full have been issued,
> - or after the content has been read in memory.
> - etc.
>
> Is there any potential big risk there? Correct me if I am wrong.
The main risc is not a corrupt file or broken list. The risc is, that a
ctid in the list points at a tuple that is not dead anymore. To avoid
that risc you would need to:
1. keep the vacuum lock open
2. leave the vacuum tx open
(or reevaluate visibility of list members upon resume)
Andreas
From | Date | Subject | |
---|---|---|---|
Next Message | Zeugswetter Andreas ADI SD | 2007-02-28 10:40:29 | Re: COMMIT NOWAIT Performance Option |
Previous Message | Zeugswetter Andreas ADI SD | 2007-02-28 10:19:44 | Re: Resumable vacuum proposal and design overview |