On Fri, Apr 24, 2015 at 6:38 AM, Heikki Linnakangas <hlinn...@iki.fi> wrote: > I wrote a little overview text on how unique and exclusion constraints are > enforced. Most of the information can be gleaned from comments elsewhere, > but I think it's helpful to have it in one place. Makes it easier to compare > how unique and exclusion constraints work. The harmless deadlocks with > exclusion constraints are not explained elsewhere AFAICS.
FWIW, both Jeff Davis and Tom Lane were well aware of this issue back when exclusion constraints went in - it was judged to be acceptable at the time, which I agree with. I happened to discuss this with Jeff in New York recently. I agree that it should definitely be documented like this (and the fact that ordinary unique indexes are unaffected, too). > This is also in preparation for Peter's INSERT ON CONFLICT patch. That will > add another section explaining how the deadlocks and livelocks are avoided. > That's easier to understand after you grok the potential for deadlocks with > exclusion constraints. Makes sense. > This also removes a comment from 1989 claiming that the code should be moved > elsewhere. I think the code is in the right place. +1 -- Peter Geoghegan -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
