Re: [PERFORM] DELETE vs TRUNCATE explanation

Robert Haas <robertmhaas(at)gmail(dot)com> writes:
> Unfortunately, there are lots of important operations (like bulk
> loading, SELECT * FROM bigtable, and VACUUM notverybigtable) that
> inevitably end up writing out their own dirty buffers. And even when
> the background writer does write something, it's not always clear that
> this is a positive thing. Here's Greg Smith commenting on the
> more-is-worse phenonmenon:

> http://archives.postgresql.org/pgsql-hackers/2012-02/msg00564.php

> Jeff Janes and I came up with what I believe to be a plausible
> explanation for the problem:

> http://archives.postgresql.org/pgsql-hackers/2012-03/msg00356.php

> I kinda think we ought to be looking at fixing that for 9.2, and
> perhaps even back-patching further, but nobody else seemed terribly
> excited about it.

I'd be fine with back-patching something like that into 9.2 if we had
(a) a patch and (b) experimental evidence that it made things better.
Unless I missed something, we have neither. Also, I read the above
two messages to say that you, Greg, and Jeff have three different ideas
about exactly what should be done, which is less than comforting for
a last-minute patch...

regards, tom lane