Example 1

Let’s assume you are trying to seed your database using the seeding script and schema shown below.

import { bloodPressure } from './schema.ts';

async function main() {
  const db = drizzle(...);
  await seed(db, { bloodPressure });
}
main();

import { serial, pgTable, integer, doublePrecision } from "drizzle-orm/pg-core";

export const users = pgTable("users", {
    id: serial("id").primaryKey(),
});

export const bloodPressure = pgTable("bloodPressure", {
	bloodPressureId: serial().primaryKey(),
	pressure: doublePrecision(),
	userId: integer().references(() => users.id).notNull(),
})

If the bloodPressure table has a not-null constraint on the userId column, running the seeding script will cause an error.

Error: Column 'userId' has not null constraint, 
and you didn't specify a table for foreign key on column 'userId' in 'bloodPressure' table.

At this point, you have several options to resolve the error:

• You can remove the not-null constraint from the userId column;
• You can expose users table to seed function schema

await seed(db, { bloodPressure, users });

• You can refine the userId column generator;

Example 2

import { bloodPressure } from './schema.ts';

async function main() {
  const db = drizzle(...);
  await seed(db, { bloodPressure });
}
main();

import { serial, pgTable, integer, doublePrecision } from "drizzle-orm/pg-core";

export const users = pgTable("users", {
    id: serial("id").primaryKey(),
});

export const bloodPressure = pgTable("bloodPressure", {
	bloodPressureId: serial().primaryKey(),
	pressure: doublePrecision(),
	userId: integer().references(() => users.id),
})

By running the seeding script above you will see a warning

Column 'userId' in 'bloodPressure' table will be filled with Null values
because you specified neither a table for foreign key on column 'userId' 
nor a function for 'userId' column in refinements.

Then you will have two choices:

• If you’re okay with filling the userId column with Null values, you can ignore the warning;

• Otherwise, you can refine the userId column generator.

Refining the userId column generator

Doing so requires the users table to already have IDs such as 1 and 2 in the database.

import { bloodPressure } from './schema.ts';

async function main() {
  const db = drizzle(...);
  await seed(db, { bloodPressure }).refine((funcs) => ({
    bloodPressure: {
      columns: {
        userId: funcs.valuesFromArray({ values: [1, 2] })
      }
    }
  }));
}
main();