Adding @Generated('uuid') doesn't update Postgres column default.

[edeesis]

Feature Description

The Problem

When someone first generates the CREATE TABLE statement for a table with a generated UUID column, the PostgresQueryRunner automatically applies the DEFAULT using PostgresDriver#uuidGenerator. See here.

However, after the column has been created, if you then add a @Generated('uuid'), the migration generation will not add the DEFAULT, which is particularly frustrating because nothing in the documentation calls out that if you're using a database engine that supports UUID generation, TypeORM skips the in-app UUID generation as shown here

The Solution

Ideally the InsertQueryBuilder would be smart enough to see that the UUID column has no default, and either fall into that block to generate the UUID, or pass the UUID generator function instead of DEFAULT.

Considered Alternatives

Alternatively, the simplest solution would be to update PostgresQueryRunner#changeColumn here to generate alter column default statements.

Additional Context

Relevant Database Driver(s)

DB Type	Relevant
aurora-data-api	no
aurora-data-api-pg	no
better-sqlite3	no
cockroachdb	no
cordova	no
expo	no
mongodb	no
mysql	no
nativescript	no
oracle	no
postgres	yes
react-native	no
sap	no
sqlite	no
sqlite-abstract	no
sqljs	no
sqlserver	no

Are you willing to resolve this issue by submitting a Pull Request?

• ✅ Yes, I have the time, and I know how to start.
• ✖️ Yes, I have the time, but I don't know how to start. I would need guidance.
• ✖️ No, I don’t have the time, but I can support (using donations) development.
• ✖️ No, I don’t have the time and I’m okay to wait for the community / maintainers to resolve this issue.