Re: Proposal for background vacuum full/cluster

"Jim C. Nasby" <decibel(at)decibel(dot)org> writes:
> I'm not sure how different it is from vacuum full, though the main idea
> is that instead of locking the table you instead work in smaller pieces
> and don't block anything other than other updates.

We don't have any support for locking sections of a table larger than
a page, so I'm not clear on how the above could be made to work.

But in any case, I wasn't talking about vacuum full. I was thinking of
the total picture in a normal vacuum cycle:

1. vacuum cleans out dead tuples and records the space in FSM
2. ordinary inserts and updates use the space shown in FSM
3. next vacuum cleans out the space freed, and shortens the table
if it can

I believe that step 2 preferentially uses space closer to the front
of the table, so I think that what you are proposing already happens
naturally.

regards, tom lane