Re: [ANNOUNCE] IMCS: In Memory Columnar Store for PostgreSQL

 But on Windows, segments are *automatically*
destroyed *by the operating system* when the last process unmaps them,
so it's not quite so clear to me how we can allow it there.  The main
shared memory segment is no problem because the postmaster always has
it mapped, even if no one else does, but that doesn't help for dynamic
shared memory segments.

Surely you just need to DuplicateHandle into the parent process?  If you
want to (tidily) dispose of it at some time, then you'll need to tell the
postmaster that you have done so and what the handle is in its process,
but if you just want it to stick around, then you can just pass it up.