questions about the logical decoding implementation

1. Why do the files holding the spilled transaction data in reorderbuffer.c
have a ".snap" suffix?

2. Those files can get quite large. Would it be reasonable to store them in
another directory (e.g. pg_replslot_tmp) so that they can be placed on
another mount point? It would also simplify the cleanup code.

3. Why are the files in pg_logical/snapshots (which also have a ".snap"
extension) stored on disk at all? If I remove them and restart, they get
recreated during decoding. The code adds a fair amount of complexity so I
assume there's an important reason.

Regards,
    Jeff Davis