| From: | Robert Haas <robertmhaas(at)gmail(dot)com> |
|---|---|
| To: | Christopher Browne <cbbrowne(at)gmail(dot)com> |
| Cc: | Kevin Grittner <Kevin(dot)Grittner(at)wicourts(dot)gov>, greg(at)2ndquadrant(dot)com, pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: Page Checksums |
| Date: | 2011-12-21 15:36:56 |
| Message-ID: | CA+TgmoZF54QDBvcN5pZ_3j5rBMVe9pT62==15QW8ucnz-_otCw@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Tue, Dec 20, 2011 at 12:12 PM, Christopher Browne <cbbrowne(at)gmail(dot)com> wrote:
> This seems to be a frequent problem with this whole "doing CRCs on pages" thing.
>
> It's not evident which problems will be "real" ones.
That depends on the implementation. If we have a flaky, broken
implementation such as the one proposed, then, yes, it will be
unclear. But if we properly guard against a torn page invalidating
the CRC, then it won't be unclear at all: any CRC mismatch means
something bad happened.
Of course, that may be fairly expensive in terms of performance. But
the only way I can see to get around that problem is to rewrite our
heap AM or our MVCC implementation in some fashion that gets rid of
hint bits.
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
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