How do you set a custom default unique id string for the @PrimaryGeneratedColumn in a TypeORM Entity?

Question

I have a use case that calls for a custom string primary key in my tables. (I don't want to use the default 'uuid' provided by GraphQL, but instead want to use the shortid library to generate a custom unique id instead.)

I'm a TypeORM beginner, and I'm not finding anything about setting a custom default primary key in the docs. Is it possible to achieve what I want in the TypeORM PrimaryGeneratedColumn, or do I have to accomplish what I want by other means?

UPDATE: I learned I can use the @BeforeInsert listener to modify entities before saving them, but TypeORM still doesn't let me override the PrimaryGeneratedColumn('uuid') and use a shortId string because the shortId string is not a valid uuid.

Tipcat

Depending on which database you are using, specifing @PrimaryGeneratedColumn('uuid') means that the database field type will be uuid, which you can't insert a non-valid UUID in. I'd suggest decorating with @PrimaryColumn('char', { length: <shortId length> }) and using a @BeforeInsert listener as you describe. This will give you a fixed-length character primary key for the shortId. – Fahy

Looking again at the shortId docs, I noticed that the generated ID may be variable length; if so you'll want to use @PrimaryColumn('varchar', { length: <max-shortid-length> }) instead of the above... – Fahy

@PrimaryColumn is exactly what I needed. I'm such a noob I didn't even know PrimaryColumn was a decorator :# my code ended up looking like this @PrimaryColumn('varchar', { default: shortid.generate(), length: 14 }) thanks for your help! I'd vote up your comments but it won't let me :/ – Tipcat

Posted as answer so you can up-vote it! BTW with the column default option, are you passing the function itself (ie default: shortid.generate) or calling it and defaulting to its return value (default: shortid.generate())? Unless I'm mistaken you'll need the former - otherwise TypeORM will have a single default value each time your app starts and will allow inserting one record but then error with a duplicate key violation for subsequent records. – Fahy

@Fahy you are correct, I ran into duplicate key violation. However, when I tried the change you recommended, I kept running into a column "gz68lzqnmn" does not exist (the id changes each time) error. The only way around this I found was to keep default: shortid.generate() but then in the BeforeInsert hook I added this.id = shortid.generate(). Very hacky and sad :( but it works. If you want to look further into this you could pull this repo and yarn start to reproduce. No pressure though. Thanks again! github.com/podverse/podverse-api/tree/primaryDefaultBug – Tipcat

I'm pretty sure this is a quoting issue - the returned ID isn't quoted so is being interpreted as a column. Wrapping shortid.generate() and quoting the value should be all that is needed - e.g. default: () => `'${shortid.generate()}'` (note the single quotes around the ID). – Fahy

Answer 1

The @PrimaryGeneratedColumn('uuid') decorator maps the column to a uuid database field type if the database supports it, which means the column values must be a valid UUIDs.

For your scenario I suggest decorating with: typescript @PrimaryColumn('varchar', { length: <max shortId length>, default: () => `'${shortid.generate()}'` })

Fahy

Answer 2

@Timshel's answer does not work when using SQLite, because default values must be constant. It gives the following error:

UnhandledPromiseRejectionWarning: QueryFailedError: SQLITE_ERROR: default value of column [id] is not constant

Instead, you can use @BeforeInsert to achieve the desired result, like so:

@Field(() => ID)
@PrimaryColumn("varchar", {
  length: 20
})
id: string;

@BeforeInsert()
setId() {
  this.id = shortid.generate();
}

Neel

@Timshel's answer also doesn't work for most other drivers. I tested it out using MySQL and when I created a migration from my entity the migration included: ALTER TABLE user CHANGE id id char(36) NOT NULL DEFAULT 177f7044-0805-4891-870e-8352cffa77bf. Looks like if you want TypeORM to do the value generation you have to use @BeforeInsert – Patchwork

other problem arises as it's either not possible to update entities OR its possible to expose a way to create entities with arbitrary IDs – Vegetative

Please note that you have to pass an instance of the entity (and not a plain object) to the save() method. – Sisile

Answer 3

Great thanks to the answers from Timshel and Oskari Liukku!

There is a complementary to their answer.

Recently, shortid was depricated, and on their main page they recommend to use nanoid.

nanoid on npm

Brinna

But what if nanoid will create id with the same value? You wil get an error, no? – Belew