hi.
https://git.postgresql.org/cgit/postgresql.git/commit/?id=11bd8318602fc2282a6201f714c15461dc2009c6
+ Adding a column with a volatile <literal>DEFAULT</literal>
+ (e.g., <function>clock_timestamp()</function>), a generated column
+ (e.g., <literal>GENERATED BY DEFAULT AS IDENTITY</literal>), a domain
+ data type with constraints will require the entire table and its
+ indexes to be rewritten, as will changing the type of an existing
+ column. As an exception, when changing the type of an existing column,
+ if the <literal>USING</literal> clause does not change the column
+ contents and the old type is either binary coercible to the new type
+ or an unconstrained domain over the new type, a table rewrite is not
+ needed.
In the current development branch,
virtual generated columns still do not support the domain.
you can not change the generation expression if it contains a check
constraint on it.
so virtual generated columns don't need rewriting.
IMHO, the committed doc description didn't mention this exception.
we need some text to cover this exception?
