| From: | Robert Haas <robertmhaas(at)gmail(dot)com> |
|---|---|
| To: | Peter Geoghegan <pg(at)bowt(dot)ie> |
| Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Bruce Momjian <bruce(at)momjian(dot)us>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org> |
| Subject: | Re: better page-level checksums |
| Date: | 2022-06-15 02:21:16 |
| Message-ID: | CA+TgmoZtec+o_3UYyEZLQ6AhtPSu5QS_W7Kfj07_fKKbt6YGGw@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Tue, Jun 14, 2022 at 9:56 PM Peter Geoghegan <pg(at)bowt(dot)ie> wrote:
> Technically we don't already do that today, with the 16-bit checksums
> that are stored in PageHeaderData.pd_checksum. But we do something
> equivalent: low-level tools can still infer that checksums must not be
> enabled on the page (really the cluster) indirectly in the event of a
> 0 checksum. A 0 value can reasonably be interpreted as a page from a
> cluster without checksums (barring page corruption). This is basically
> reasonable because our implementation of checksums is guaranteed to
> not generate 0 as a valid checksum value.
I don't think that 'pg_checksums -d' zeroes the checksum values on the
pages in the cluster.
--
Robert Haas
EDB: http://www.enterprisedb.com
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