Re: POC: Sharing record typmods between backends

Hi,

On 2017-09-04 18:14:39 +1200, Thomas Munro wrote:
> Thanks for the review and commits so far. Here's a rebased, debugged
> and pgindented version of the remaining patches.

I've pushed this with minor modifications:
- added typedefs to typedefs.list
- re-pgindented, there were some missing reindents in headers
- added a very brief intro into session.c, moved some content repeated
in various places to the header - some of them were bound to become
out-of-date due to future uses of the facility.
- moved NULL setting in detach hook directly after the respective
resource deallocation, for the not really probable case of it being
reinvoked due to an error in a later dealloc function

Two remarks:
- I'm not sure I like the order in which things are added to the typemod
hashes, I wonder if some more careful organization could get rid of
the races. Doesn't seem critical, but would be a bit nicer.

- I'm not yet quite happy with the Session facility. I think it'd be
nicer if we'd a cleaner split between the shared memory notion of a
session and the local memory version of it. The shared memory version
would live in a ~max_connections sized array, referenced from
PGPROC. In a lot of cases it'd completely obsolete the need for a
shm_toc, because you could just store handles etc in there. The local
memory version then would just store local pointers etc into that.

But I think we can get there incrementally.

It's very nice to push commits that have stats like
6 files changed, 27 insertions(+), 1110 deletions(-)
even if it essentially has been paid forward by a lot of previous work
;)

Thanks for the work on this!

Regards,

Andres