Hi folks
The attached patch expands the xfunc docs and bgworker docs a little, providing a starting point for developers to learn how to do some common tasks the Postgres Way.
It mentions in brief these topics:
* longjmp() based exception handling with elog(ERROR), PG_CATCH() and PG_RE_THROW() etc
* Latches, spinlocks, LWLocks, heavyweight locks, condition variables
* shm, DSM, DSA, shm_mq
* syscache, relcache, relation_open(), invalidations
* deferred signal handling, CHECK_FOR_INTERRUPTS()
* Resource cleanup hooks and callbacks like on_exit, before_shmem_exit, the resowner callbacks, etc
* signal handling in bgworkers
All very superficial, but all things I really wish I'd known a little about, or even that I needed to learn about, when I started working on postgres.
I'm not sure it's in quite the right place. I wonder if there should be a separate part of xfunc.sgml that covers the slightly more advanced bits of postgres backend and function coding like this, lists relevant README files in the source tree, etc.
I avoided going into details like how resource owners work. I don't want the docs to have to cover all that in detail; what I hope to do is start providing people with clear references to the right place in the code, READMEs, etc to look when they need to understand specific topics.
