| From: | "Jonah H(dot) Harris" <jonah(dot)harris(at)gmail(dot)com> |
|---|---|
| To: | "Alvaro Herrera" <alvherre(at)commandprompt(dot)com> |
| Cc: | "Pg Hackers" <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Block-level CRC checks |
| Date: | 2008-10-17 15:42:39 |
| Message-ID: | 36e682920810170842w1ff3e521ncdf691e65c378f4c@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Fri, Oct 17, 2008 at 11:26 AM, Alvaro Herrera
<alvherre(at)commandprompt(dot)com> wrote:
> So this discussion died with no solution arising to the
> hint-bit-setting-invalidates-the-CRC problem.
I've been busy.
> Apparently the only solution in sight is to WAL-log hint bits. Simon
> opines it would be horrible from a performance standpoint to WAL-log
> every hint bit set, and I think we all agree with that. So we need to
> find an alternative mechanism to WAL log hint bits.
Agreed.
> I thought about causing a process that's about to write a page check a
> flag that says "this page has been dirtied by someone who didn't bother
> to generate WAL". If the flag is set, then the writer process is forced
> to write a WAL record containing all hint bits in the page, and only
> then it is allowed to write the page (and thus calculate the new CRC).
Interesting idea... let me ponder it for a bit.
--
Jonah H. Harris, Senior DBA
myYearbook.com
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