Re: Turning off HOT/Cleanup sometimes

Stephen Frost <sfrost(at)snowman(dot)net> writes:
> That said, I'm not entirely convinced that traversing these dead tuples
> is all *that* painful during SELECT. If there's that many levels then
> hopefully it's not long til an UPDATE comes along and cleans them up.

There's always VACUUM ;-)

If you take about ten steps back, what's happening here is that
maintenance work that we'd originally delegated to VACUUM, precisely so
that it wouldn't have to be done by foreground queries, is now being done
by foreground queries. And oddly enough, people don't like that.

There is a reasonable argument for forcing UPDATE queries to do it anyway,
to improve the odds they can do same-page updates (whether HOT or
otherwise). And probably an INSERT should do it on a page that it's
selected as an insertion target. But I think the argument that the
original do-maintenance-in-background-whenever-possible design was wrong
is a lot harder to sustain for SELECT or even DELETE queries. As I said
upthread, I think the current behavior was *not* chosen for performance
reasons but just to limit the scope of what we had to change for HOT.

regards, tom lane