| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Stephen Frost <sfrost(at)snowman(dot)net> |
| Cc: | Jim Nasby <Jim(dot)Nasby(at)bluetreble(dot)com>, Peter Geoghegan <pg(at)heroku(dot)com>, Petr Jelinek <petr(dot)jelinek(at)2ndquadrant(dot)com>, Magnus Hagander <magnus(at)hagander(dot)net>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Checksums by default? |
| Date: | 2017-01-24 02:47:38 |
| Message-ID: | 19271.1485226058@sss.pgh.pa.us |
| Views: | Raw Message | Whole Thread | Download mbox | Resend email |
| Thread: | |
| Lists: | pgsql-hackers |
Stephen Frost <sfrost(at)snowman(dot)net> writes:
> * Tom Lane (tgl(at)sss(dot)pgh(dot)pa(dot)us) wrote:
>> But we don't maintain the checksum of a page while it sits in shared
>> buffers. Trying to do so would break, eg, concurrent hint-bit updates.
> Hence why I said 'clean' pages..
When we write out a page, we copy it into private memory and compute the
checksum there, right? We don't copy the checksum back into the page's
shared-buffer image, and if we did, that would defeat the point because we
would've had to maintain exclusive lock on the buffer or else the checksum
might be out of date. So I don't see how this works without throwing away
a lot of carefully-designed behavior.
regards, tom lane
| From | Date | Subject | |
|---|---|---|---|
| Next Message | Andres Freund | 2017-01-24 02:51:38 | Re: Checksums by default? |
| Previous Message | Jim Nasby | 2017-01-24 02:45:33 | Re: Online enabling of page level checksums |