On 2014-01-02 02:20:02 -0800, Peter Geoghegan wrote: > On Thu, Jan 2, 2014 at 1:49 AM, Andres Freund <and...@2ndquadrant.com> wrote: > >> Well, you're not totally on your own for something like that with this > >> feature. You can project the conflicter's tid, and possibly do a more > >> sophisticated recovery, like inspecting the locked row and iterating. > > > > Yea, but in that case I *do* conflict with more than one index and old > > values need to stay locked. Otherwise anything resembling > > forward-progress guarantee is lost. > > I'm not sure I understand. In a very real sense they do stay locked. > What is insufficient about locking the definitively visible row with > the value, rather than the value itself?
Locking the definitely visible row only works if there's a row matching the index's columns. If the values of the new row don't have corresponding values in all the indexes you have the same old race conditions again. I think to be useful for many cases you really need to be able to ask for a potentially conflicting row and be sure that if there's none you are able to insert the row separately. Greetings, Andres Freund -- Andres Freund http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training & Services -- Sent via pgsql-hackers mailing list (email@example.com) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers