| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Alvaro Herrera <alvherre(at)commandprompt(dot)com> |
| Cc: | Greg Stark <greg(dot)stark(at)enterprisedb(dot)com>, Martijn van Oosterhout <kleptog(at)svana(dot)org>, Pg Hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Block-level CRC checks |
| Date: | 2008-11-10 15:33:59 |
| Message-ID: | 6767.1226331239@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
Alvaro Herrera <alvherre(at)commandprompt(dot)com> writes:
> Greg Stark wrote:
>> I'm beginning to think just excluding the hint bits would be simpler and
>> safer. If we're double buffering then it might be possible to do that
>> pretty cheaply. Copy the whole buffer with memcpy then loop through the
>> line pointers unsetting the hint bits. Then do the crc. Though that would
>> prevent us from doing "zero-copy" crc by doing it in the copy.
> The downside to this idea is that we need to create a copy of the page
> and call those routines when we read the page in, too.
Ugh. The cost on write was bad enough, but paying it on read is a lot
worse ...
regards, tom lane
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