"Florian G. Pflug" <fgp(at)phlo(dot)org> writes:
> ...
> Neither the "dealer", nor the "workers" would need access to the either
> the shared memory or the disk, thereby not messing with the "one backend
> is one transaction is one session" dogma.
> ...
Unfortunately, this idea has far too narrow a view of what a datatype
input function might do. Just for starters, consider "enum" input,
which certainly requires catalog access. We have also explicitly
acknowledged the idea that datatype I/O functions might try to store
typmod-related data in some special catalog somewhere.
regards, tom lane