Re: Online verification of checksums

From: Stephen Frost <sfrost(at)snowman(dot)net>
To: Michael Paquier <michael(at)paquier(dot)xyz>
Cc: Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, Michael Banck <michael(dot)banck(at)credativ(dot)de>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>
Subject: Re: Online verification of checksums
Date: 2019-03-18 07:38:02
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* Michael Paquier (michael(at)paquier(dot)xyz) wrote:
> On Mon, Mar 18, 2019 at 02:38:10AM -0400, Stephen Frost wrote:
> > Uh, we are, of course, going to have partial reads- we just need to
> > handle them appropriately, and that's not hard to do in a way that we
> > never have false positives.
> Ere, my apologies here. I meant the read of a torn page, not a

In the case of a torn page, we should be able to check the LSN, as
discussed extensively previously, and if the LSN is from after the
checkpoint we started at then we should be fine to skip the page.

> partial read (when extending the relation file we have locks
> preventing from a partial read as well by the way).

Yes, we do, in the backend... We don't have (nor do we need) to get
involved in those locks for these tools though..



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