| From: | Josh Berkus <josh(at)agliodbs(dot)com> |
|---|---|
| To: | Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com> |
| Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Robert Haas <robertmhaas(at)gmail(dot)com>, pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: Closing some 8.4 open items |
| Date: | 2009-04-08 17:52:34 |
| Message-ID: | 49DCE462.6070308@agliodbs.com |
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| Lists: | pgsql-hackers |
Heikki,
> It's important to distinguish what kind of fadvise we're talking about.
> The bitmap scan code issues hints about individual pages, using
> posix_fadvise(... POSIX_FADV_WILLNEED). For increasing the readahead of
> a sequential scan, you'd want to use POSIX_FADV_SEQUENTIAL. I believe
> the support for the latter is much more widespread than for the former.
OK, so this is potentially useful (pending testing) but it's a different
feature. We'll discuss it for 8.5.
The other thing I was going to ask you about is using posix_fadvise as
an alternative to O_DIRECT for the xlog. O_DIRECT is, AFAIK,
linux-only, whereas there are "direct write" fadvise flags which work on
multiple OSes.
--
Josh Berkus
PostgreSQL Experts Inc.
www.pgexperts.com
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