02.05.2024 19:21, Alvaro Herrera wrote:
Now, you could claim that the standard doesn't mention
INCLUDING/EXCLUDING CONSTRAINTS, therefore since we have come up with
its definition then we should make it affect not-null constraints.
However, there's also this note:
NOTE 520 — <column constraint>s, except for NOT NULL, are not included in
CDi; <column constraint definition>s are effectively transformed to <table
constraint definition>s and are thereby also excluded.
which is explicitly saying that not-null constraints are treated
differently; in essence, with INCLUDING CONSTRAINTS we choose to affect
the constraints that the standard says to ignore.
Thank you for very detailed and convincing explanation!
Now I see what the last sentence here (from [1]) means:
INCLUDING CONSTRAINTS
CHECK constraints will be copied. No distinction is made between
column constraints and table constraints. _Not-null constraints are
always copied to the new table._
(I hadn't paid enough attention to it, because this exact paragraph is
also presented in previous versions...)
[1] https://www.postgresql.org/docs/devel/sql-createtable.html
Best regards,
Alexander
