On Fri, Oct 7, 2022 at 2:03 PM Vik Fearing <v...@postgresfriends.org> wrote:
> On 10/4/22 09:41, Peter Eisentraut wrote: > > In PostgreSQL 10, we added identity columns, as an alternative to serial > > columns (since 6.something). They mostly work the same. Identity > > columns are SQL-conforming, have some more features (e.g., overriding > > clause), and are a bit more robust in schema management. Some of that > > was described in [0]. AFAICT, there have been no complaints since that > > identity columns lack features or are somehow a regression over serial > > columns. > > > > But clearly, the syntax "serial" is more handy, and most casual examples > > use that syntax. So it seems like we are stuck with maintaining these > > two variants in parallel forever. I was thinking we could nudge this a > > little by remapping "serial" internally to create an identity column > > instead. At least then over time, the use of the older serial > > mechanisms would go away. > > > > Note that pg_dump dumps a serial column in pieces (CREATE SEQUENCE + > > ALTER SEQUENCE ... OWNED BY + ALTER TABLE ... SET DEFAULT). So if we > > did this, any existing databases would keep their old semantics, and > > those who really need it can manually create the old semantics as well. > > > > Attached is a demo patch how the implementation of this change would > > look like. This creates a bunch of regression test failures, but > > AFAICT, those are mainly display differences and some very peculiar test > > setups that are intentionally examining some edge cases. These would > > need to be investigated in more detail, of course. > > I haven't tested the patch yet, just read it. > > Is there any reason to use BY DEFAULT over ALWAYS? I tend to prefer the > latter. > I would assume to maintain backwards compatibility with the semantics of SERIAL today? I do also prefer ALWAYS, but that would make it a compatibility break. -- Magnus Hagander Me: https://www.hagander.net/ <http://www.hagander.net/> Work: https://www.redpill-linpro.com/ <http://www.redpill-linpro.com/>
