From: | Ron Mayer <rm_pg(at)cheapcomplexdevices(dot)com> |
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To: | Merlin Moncure <merlin(dot)moncure(at)rcsonline(dot)com> |
Subject: | Re: seq scan cache vs. index cache smackdown |
Date: | 2005-02-22 01:14:19 |
Message-ID: | 421A876B.6010308@cheapcomplexdevices.com |
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Lists: | pgsql-performance |
Merlin Moncure wrote:
>
> readv and writev are in the single unix spec...and yes ...
>
> On some systems they might just be implemented as a loop inside the
> library, or even as a macro.
You sure?
Requirements like this:
http://www.opengroup.org/onlinepubs/007908799/xsh/write.html
"Write requests of {PIPE_BUF} bytes or less will not be
interleaved with data from other processes doing writes
on the same pipe."
make me think that it couldn't be just a macro; and if it
were a loop in the library it seems it'd still have to
make sure it's done with a single write system call.
(yeah, I know that requirement is just for pipes; and I
suppose they could write a loop for normal files and a
different special case for pipes; but I'd be surprised).
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