Re: [PERFORMANCE] Insights: fseek OR read_cluster?

On 24/09/2011 2:49 PM, Antonio Rodriges wrote:
> Hello,
>
> It is interesting how PostgreSQL reads the tablefiie.
> Whether its indexes store/use filesystem clusters locations containing
> required data (so it can issue a low level cluster read) or it just
> fseeks inside a file?

What is read_cluster()  ? Are you talking about some kind of async 
and/or direct I/O? If so, PostgreSQL is not designed for direct I/O, it 
benefits from using the OS's buffer cache, I/O scheduler, etc.

IIRC Pg uses pread() to read from its data files, but I didn't go double 
check in the sources to make sure.

--
Craig Ringer