On 15 April 2013 20:52, Robert Haas <robertmh...@gmail.com> wrote: > On Mon, Apr 15, 2013 at 11:49 AM, Tom Lane <t...@sss.pgh.pa.us> wrote: >>> I claim this is a common class, since sequence next_val functions and >>> uuid generators meet that criteria and most common forms of auditing >>> trigger, as well as any other form of data-reformatting trigger. >> >> I don't believe that it's a good idea to consider nextval() to be >> reorderable, so I'm not convinced by your argument here. > > Why not? > > I admit that I can't convince myself that it's safe. But I can't > think of a concrete example where it breaks anything, either.
I'm not sure exactly if the corect label is "reorderable" or some other word that describes this specific situation. "Parallel independent" probably would work, since if we had a DML statement that worked in 2 separate processes we'd probably want to know that the rows in each could be divided up without changing the result. It looks straightforward to put in a special case check for sequences, which is the most important use case. Sequences are a recognised database object, so such a special case could be justified... shame about the other use cases though, e.g. UUIDs. I guess we can generalise it when we have a better idea of whether this does indeed make a useful generalisation. -- Simon Riggs http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training & Services -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
