Re: How much do the hint bits help?

On Tue, 2010-12-21 at 17:42 -0500, Merlin Moncure wrote:

> *) is there community interest in a full patch that fills in the
> missing details not implemented here?

You're thinking seems sound to me. We now have all-visible flags, fewer
xids, much better clog concurrency. Avoiding hint bits would also
noticeably reduce number of dirty writes, especially at checkpoint.

Hot Standby already ignores hint bits and I've not heard a single
complaint, so we are already doing this in the code.

I don't see any reason to believe that there is not an equally effective
optimisation that we can apply to bring performance back up, if it is
shown to drop in particular use cases.

I would vote to put this into 9.1 as a non-default option at restart,
opening the door to other features which hint bits are frustrating.
People can then choose between those features and the "power of hint
bits". I think many people would choose db block checksums.

If you need support, or direct help with the code, just ask. Am happy to
be your committer also.

--
Simon Riggs http://www.2ndQuadrant.com/books/
PostgreSQL Development, 24x7 Support, Training and Services