Re: odd postgresql performance (excessive lseek) - Mailing list pgsql-performance

From Tom Lane
Subject Re: odd postgresql performance (excessive lseek)
Date
Msg-id 10133.1287498969@sss.pgh.pa.us
Whole thread Raw
In response to Re: odd postgresql performance (excessive lseek)  (Jon Nelson <jnelson+pgsql@jamponi.net>)
Responses Re: odd postgresql performance (excessive lseek)  (Jon Nelson <jnelson+pgsql@jamponi.net>)
Re: odd postgresql performance (excessive lseek)  (Robert Haas <robertmhaas@gmail.com>)
List pgsql-performance
Jon Nelson <jnelson+pgsql@jamponi.net> writes:
> This is another situation where using pread would have saved a lot of
> time and sped things up a bit, but failing that, keeping track of the
> file position ourselves and only lseek'ing when necessary would also
> help.

No, it wouldn't; you don't have the slightest idea what's going on
there.  Those lseeks are for the purpose of detecting the current EOF
location, ie, finding out whether some other backend has extended the
file recently.  We could get rid of them, but only at the cost of
putting in some other communication mechanism instead.

            regards, tom lane

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