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.
