Re: Re: Rethinking hint bits WAS: Protecting against unexpected zero-pages: proposal

Greg, Tom,

> We *already* have separate bitmap outside the table for transaction
> commit bits. It's the clog.

You didn't read my whole e-mail. I talk about the CLOG further down.

> Josh is ignoring the proposal that is on the table and seems actually
> workable, which is to consult the visibility map during index-only
> scans. For mostly-static tables this would save trips to the heap for
> very little extra I/O. The hard part is to make the VM reliable, but
> that is not obviously harder than making separately-stored hint bits
> reliable.

No, I'm not. I'm pointing out that it doesn't unblock the other 4
features/improvements I mentioned, *all* of which would be unblocked by
not storing the hint bits in the table, whatever means we use to do so.
You, for your part, are consistently ignoring these other issues.

--
-- Josh Berkus
PostgreSQL Experts Inc.
http://www.pgexperts.com