outline/server/migrations/20191119023013-cascade-backlinks2.js

const tableName = 'backlinks';

// because of this issue in Sequelize the foreign key constraint may be named differently depending
// on when the previous migrations were ran https://github.com/sequelize/sequelize/pull/9890
const constraintNames = ['backlinks_documentId_fkey', 'documentId_foreign_idx'];

module.exports = {
  up: async (queryInterface, Sequelize) => {
    let error;
    for (const constraintName of constraintNames) {
      try {
        await queryInterface.sequelize.query(`alter table "${tableName}" drop constraint "${constraintName}"`)
        await queryInterface.sequelize.query(
          `alter table "${tableName}"
            add constraint "${constraintName}" foreign key("documentId") references "documents" ("id")
            on delete cascade`
        );
        return;
      } catch (err) {
        error = err;
      }
    }
    throw error;
  },

  down: async (queryInterface, Sequelize) => {
    let error;
    for (const constraintName of constraintNames) {
      try {
        await queryInterface.sequelize.query(`alter table "${tableName}" drop constraint "${constraintName}"`)
        await queryInterface.sequelize.query(
          `alter table "${tableName}"\
            add constraint "${constraintName}" foreign key("documentId") references "documents" ("id")
            on delete no action`
        );
        return;
      } catch (err) {
        error = err;
      }
    }
    throw error;
  },
};