Hi, Moving discussion to -hackers, this isn't really a bug, it's an architectural issue with the new in-tree approach.
Short recap: With the patch applied in [1] ff, sequences partially behave transactional (because pg_sequence is updated transactionally), partially non-transctionally (because there's no locking enforcing it, and it's been stated as undesirable to change that). This leads to issues like described in [2]. For more context, read the whole discussion. On 2017-05-03 23:29:29 -0400, Peter Eisentraut wrote: > I'm working on this and will report on Friday. What's the plan here? I think the problem is that the code as is is trying to marry two incompatible things: You're trying to make nextval() not block, but have ALTER SEQUENCE be transactional. Given MAXVAL, INCREMENT, etc. those two simply aren't compatible. I think there's three basic ways to a resolution here: 1. Revert the entire patch for now. That's going to be very messy because of the number of followup patches & features. 2. Keep the catalog, but only ever update the records using heap_inplace_update. That'll make the transactional behaviour very similar to before. It'd medium-term also allow to move the actual sequence block into the pg_sequence catalog itself. 3. Keep the catalog, make ALTER properly transactional, blocking concurrent nextval()s. This resolves the issue that nextval() can't see the changed definition of the sequence. I think this really needs design agreement from multiple people, because any of these choices will have significant impact. To me 3. seems like the best approach long-term, because both the current and the <v10 behaviour certainly is confusing and inconsistent (but in different ways). But it'll be quite noticeable to users. - Andres [1] http://git.postgresql.org/gitweb/?p=postgresql.git;a=commit;h=1753b1b027035029c2a2a1649065762fafbf63f3 [2] http://archives.postgresql.org/message-id/20170427062304.gxh3rczhh6vblrwh%40alap3.anarazel.de -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
