Florian Pflug <fgp.phlo.org@gmail.com> writes:
> I was under the impression that pruning *does* free the space occupied
> by DEAD HOT-Tuples (minus the size of a redirection line pointer). It
> just doesn't defragment, so how much of that freed space you can actually
> use to store new tuples is another question...
None, unless the freed tuple happens to be directly adjacent to the
pd_lower --- pd_upper hole, or unless the patch has done a lot more to
the page-free-space-management code than I thought. We have never
looked for free space anywhere except the main "hole".
regards, tom lane