Hot standby status

There's been a lot of churn in hot standby since the beginning of the
commitfest, so I thought it would be good to summarize where we are.

Attached is the latest and greatest patch against CVS head, taken from
the hs-riggs branch in my git repository where I've been working on this.

Here's a list of TODOs/issues that've already been mentioned.

- clarify default_transaction_read_only and transaction_read_only
http://archives.postgresql.org/message-id/4AB75A61.6040505@enterprisedb.com

- allow connections after a shutdown checkpoint

- don't clear locks belonging to prepared transactions at startup

- rename references to "loggable locks" to "AccessExclusiveLocks in
master" or similar

- race condition in xact_redo_commit/abort
(http://archives.postgresql.org/message-id/4ABF539F.8050305@enterprisedb.com)

- connection goes out of sync when an idle-in-transaction transaction is
killed
(http://archives.postgresql.org/message-id/4ACF77A5.1070706@enterprisedb.com)

Before this is committed, there's some debug code that ought to be removed:

- PostAuthDelay in startup process. Or maybe that should be left in, but
some doc changes would then be in order. I'm inclined to remove it though.
- the CleanupWaitStats stuff. If we want something like this, I'd like
to see it integrated into existing pg_stat views.

Let me know if I'm missing something. And please feel free to help, by
testing, by reviewing and commenting on the patch, or by addressing any
of the above issues. I will continue working on this, but this is a big
patch so any help is much appreciated.

--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com