Support postgres column with varchar datatype and uuid_generate_v4() default

[knarfchan]

Feature Description

A new column option for generated called default that represents a column generated by whatever default function a column.

@Column({
    name: "some_uuid_column",
    default: () => "uuid_generate_v4()",
    generated: "default",
    type: "varchar",
    length: 256,
  })

The Problem

Right now there's no way for an Entity column to represent a column in Postgres that has varchar data type and uuid_generate_v4() default.

Typeorm thinks that any column with uuid_generate_v4() default should have generationStrategy uuid, and it thinks that anything with generationStrategy uuid should be of data type uuid. This causes Typeorm to constantly try to drop and re-create any column that tries to define a varchar column with default uuid_generate_v4() when generating a migration.

The Solution

I tried patching the Typeorm library with a new generated type called default and mapping non uuid columns with uuid_generate_v4() to this default. Then when defining the column, I can define it like below and this seems to work.

@Column({
    name: "some_uuid_column",
    default: () => "uuid_generate_v4()",
    generated: "default",
    type: "varchar",
    length: 256,
  })

Considered Alternatives

Is there anything special about a column marked as generated in this case? Might be better just to parse Postgres columns with varchar datatype and uuid_generate_v4 to have isGenerated = false. Happy to go this route if it makes sense and is simpler.

Additional Context

I need to match the database's column definition as is because it's a huge table and there multiple of them, so I need the typeorm column definition to conform to the column instead of vice versa.

Relevant Database Driver(s)

DB Type	Relevant
aurora-mysql	no
aurora-postgres	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
spanner	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.

Any guidance would be great! Thanks!

[knarfchan]

The more I look into it, the more it makes sense to pursue the alternative.