Feedback on writing extensible modules

Some feedback

1. Want some very clear and supported way to know whether Postgres is
fully up. Currently, if you write _PG_init you sometimes need to know if
it is being executed by LOAD or as a reload. So actual initialisation
sometimes needs to happen outside of _PG_init.

2. shmem_startup_hook doesn't allow multiple modules to create shmem.
All callers of the hook think they are the only caller, causing chaos if
multiple people need this. Currently, whoever sets up the hook gets to
create shmem. (There's no docs for this yet). Would prefer something
like RequestAddinShmemSpace() which can be called by multiple callers.

-- Simon Riggs           www.2ndQuadrant.comPostgreSQL Training, Services and Support