Re: Emit fewer vacuum records by reaping removable tuples during pruning

On Mon, Jan 08, 2024 at 03:50:47PM -0500, Robert Haas wrote:
> Hmm, interesting. I haven't had time to study this fully today, but I
> think 0001 looks fine and could just be committed. Hooray for killing
> useless variables with dumb names.

I've been looking at 0001 a couple of weeks ago and thought that it
was fine because there's only one caller of lazy_scan_prune() and one
caller of lazy_scan_noprune() so all the code paths were covered.

+ /* rel truncation is unsafe */
+ if (hastup)
+ vacrel->nonempty_pages = blkno + 1;

Except for this comment that I found misleading because this is not
about the fact that truncation is unsafe, it's about correctly
tracking the the last block where we have tuples to ensure a correct
truncation. Perhaps this could just reuse "Remember the location of
the last page with nonremovable tuples"? If people object to that,
feel free.
--
Michael