Re: Online verification of checksums - Mailing list pgsql-hackers

From Stephen Frost
Subject Re: Online verification of checksums
Date
Msg-id 20190318073802.GM6197@tamriel.snowman.net
Whole thread Raw
In response to Re: Online verification of checksums  (Michael Paquier <michael@paquier.xyz>)
List pgsql-hackers
Greetings,

* Michael Paquier (michael@paquier.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..

Thanks!

Stephen

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