Support DEFAULT expression

[forrest-akin]

Column defaults in CREATE TABLE statements should, in addition to value literals, support expressions. For example, it's very common for a column of type uuid to default to either gen_random_uuid() or uuid_generate_v4(). Ideally, ColumnSpec::Default(Value) would contain a SimpleExpr instead of Value since SimpleExpr has aValue variant. This obviously would be a breaking change so perhaps instead consider adding ColumnSpec::DefaultExpr(SimpleExpr).

[tyt2y3]

The extra() method can be used to append expressions to the column definition.

I think default value and default expression are different things, but yes, if we have a DefaultExpr variant, we could probably make the default method to accept both Value and SimpleExpr. That say, we do not have symbols for all the database builtin functions yet (that'd be a nice-to-have), so perhaps for now extra() is your friend.

[forrest-akin]

Nice, will give that a shot 🙏

[tyt2y3]

@forrest-akin got success?

[forrest-akin]

Oops, forgot to check back. Yup, .extra() works for now for default expressions 👌