no-add-not-null-without-default

Reports a NOT NULL column added to an existing table without a default, which fails as soon as the table has rows.

Category	Default severity	Databases
locking	error	PostgreSQL

What happens

When a column is added, PostgreSQL gives every existing row the column's default. With no default, that value is NULL, and the NOT NULL constraint rejects it: ERROR: column "nickname" of relation "users" contains null values. The migration fails on every environment that has data, often only in production.

Identity and generated columns get their values from elsewhere and are not reported here. Statements on a table created in the same migration are not reported: the table has no rows yet.

Bad

What migration:generate writes for a new @Column() nickname: string:

import { MigrationInterface, QueryRunner } from 'typeorm'

export class AddUserNickname1727200000000 implements MigrationInterface {
  public async up(queryRunner: QueryRunner): Promise<void> {
    await queryRunner.query(`ALTER TABLE "users" ADD "nickname" character varying NOT NULL`)
  }

  public async down(queryRunner: QueryRunner): Promise<void> {
    // ...
  }
}

Safe

Give the column a constant default. Since PostgreSQL 11 this needs no table rewrite:

import { MigrationInterface, QueryRunner } from 'typeorm'

export class AddUserNickname1727200000000 implements MigrationInterface {
  public async up(queryRunner: QueryRunner): Promise<void> {
    await queryRunner.query(
      `ALTER TABLE "users" ADD "nickname" character varying NOT NULL DEFAULT ''`,
    )
  }

  public async down(queryRunner: QueryRunner): Promise<void> {
    // ...
  }
}

In the entity: @Column({ default: '' }). If there is no sensible default, add the column as nullable, backfill it in batches, and then enforce NOT NULL without a long lock, as no-set-not-null describes.

When to suppress

When the table is known to be empty in every environment.

// preflight safety-assured no-add-not-null-without-default -- feature table, created empty in 2.3

References

• PostgreSQL: ALTER TABLE, notes ("If no column constraints are specified, NULL is used as the DEFAULT", and a non-volatile default needs no rewrite)
• orm-preflight lock verification results