Horton

Re: Use pread and pwrite instead of lseek + write and read

Victor Wagner <vitus@wagner.pp.ru>

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From: Victor Wagner <vitus@wagner.pp.ru>
To: pgsql-hackers@postgresql.org
Date: 2016-08-17T09:34:37Z
Lists: pgsql-hackers 
On Wed, 17 Aug 2016 10:58:09 +0300
Oskari Saarenmaa <os@ohmu.fi> wrote:



> 
> The attached patch replaces FileWrite and FileRead with FileWriteAt
> and FileReadAt and removes most FileSeek calls.  FileSeek is still
> around so we can find the end of a file, but it's not used for
> anything else.

It seems that configure test for availability of pread/pwrite functions
and corresponding #define is needed.
 
I don't think that all platforms, supported by PostgreSQL support this
API. Especially, I cannot find any mention of pread/pwrite in the Win32 
except this thread on stackoverflow:


http://stackoverflow.com/questions/766477/are-there-equivalents-to-pread-on-different-platforms

Commits

  1. Use pg_pread() and pg_pwrite() for data files and WAL.