Hi!
Existing TOAST has several very painful drawbacks - lack of UPDATE
operation, bloating of TOAST tables, and limits that are implicitly implied
on base tables by their TOAST tables, so it is seems not fair to say that
Pluggable TOAST does not solve any problems but just introduces new
ones.
The main reason behind this decision is that keeping the first implementation
on the side of the vanilla (I mean rebasing it) over time is very difficult due
to the very invasive nature of this solution.
So we decided to reduce changes in the core to the minimum necessary
to make it available through the hooks, because the hooks part is very
lightweight and simple to keep rebasing onto the vanilla core. We plan
to keep this extension free with the PostgreSQL license, so any PostgreSQL
user could benefit from the TOAST on steroids, and sometimes in the
future it will be a much simpler task to integrate the Pluggable TOAST into
the vanilla, along with our advanced TOAST implementations which
we plan to keep under Open Source licenses too.