Re: Online verification of checksums

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Michael Banck <michael(dot)banck(at)credativ(dot)de>
Cc: Asif Rehman <asifr(dot)rehman(at)gmail(dot)com>, pgsql-hackers(at)lists(dot)postgresql(dot)org
Subject: Re: Online verification of checksums
Date: 2020-04-06 20:45:44
Views: Raw Message | Whole Thread | Download mbox | Resend email
Lists: pgsql-hackers

I wrote:
> Another thing that's bothering me is that the patch compares page LSN
> against GetInsertRecPtr(); but that function says
> ...
> I'm not convinced that an approximation is good enough here. It seems
> like a page that's just now been updated could have an LSN beyond the
> current XLOG page start, potentially leading to a false checksum
> complaint. Maybe we could address that by adding one xlog page to
> the GetInsertRecPtr result? Kind of a hack, but ...

Actually, after thinking about that a bit more: why is there an LSN-based
special condition at all? It seems like it'd be far more useful to
checksum everything, and on failure try to re-read and re-verify the page
once or twice, so as to handle the corner case where we examine a page
that's in process of being overwritten.

regards, tom lane

In response to


Browse pgsql-hackers by date

  From Date Subject
Next Message Grigory Smolkin 2020-04-06 20:46:01 Re: archive recovery fetching wrong segments
Previous Message Tomas Vondra 2020-04-06 20:42:22 Re: [PATCH] Incremental sort (was: PoC: Partial sort)