Re: foreign key locks

I just pushed this patch to the master branch.  There was a
corresponding catversion bump and pg_control version bump.  I have
verified that "make check-world" passes on my machine, as well as
isolation tests and pg_upgrade.

Tom Lane said at one point "this is too complex to maintain".  Several
times during the development I feared he might well be right.  I am sure
he will be discovering many oversights and poor design choices, when
gets around to reviewing the code; hopefully some extra effort will be
all that's needed to make the whole thing work sanely and not eat
anyone's data.  I just hope that nothing so serious comes up that the
patch will need to be reverted completely.

This patch is the result of the work of many people.  I am not allowed
to mention the patch sponsors in the commit message, so I'm doing it
here: first and foremost I need to thank my previous and current
employers Command Prompt and 2ndQuadrant -- they were extremely kind in
allowing me to work on this for days on end (and not all of it was
supported by financial sponsors).  Joel Jacobson started the whole
effort by posting a screencast of a problem his company was having; I
hope they found a workaround in the meantime, because his post was in
mid 2010.  The key idea of this patch' design came from Simon Riggs;
Noah Misch provided additional design advice that allowed the project
torun to completion.  Noah and Andres Freund spent considerable time
reviewing early versions of this patch; they uncovered many embarrasing
bugs in my implementation.  Kevin Grittner, Robert Haas, and others,
provided useful comments as well.  Noah Misch, Andres Freund, Marti
Raudsepp and Alexander Shulgin also provided bits of code.

Any bugs that remain are, of course, my own fault only.

Financial support came from

* Command Prompt Inc. of Washington, US
* 2ndQuadrant Ltd. of United Kingdom
* Trustly (then Glue Finance) of Sweden
* Novozymes A/S of Denmark
* MailerMailer LLC of Maryland, US
* PostgreSQL Experts, Inc. of California, US.

My sincerest thanks to everyone.


I seriously hope that no patch of mine ever becomes this monstruous
again.

--
Álvaro Herrera                http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services