续集更新多行

Question

Update multiple rows, is using a bulk update a good solution or something like the code below works? . I supposed wanted to update all the records with the id and filename.

I did try to update inside a loop but the migration hang up and take too long in this block. is it because of the iterations? or is there something wrong with the update syntax?. Thank you.

#Code

 for (let i = 0; i < documents.length; i++) {
        const prefix = Date.now().toString();
        const fileParts = documents[i].filename.split('.');
        const finalname = `${fileParts[0]}-${prefix}.${fileParts[1]}`;
        // eslint-disable-next-line no-await-in-loop
        await queryInterface.sequelize.query(`UPDATE ${EmployeeDocumentsModel.tableName} SET filename='${finalname}' WHERE id=${documents[i].id};`, { transaction });
      }

#CODE

module.exports = {
  up: async (queryInterface) => {
    const transaction = await queryInterface.sequelize.transaction();
    try {
      const sequelizeClient = app.get('sequelizeClient');

      const documents = await sequelizeClient.query(
        `SELECT id, filename, COUNT(filename) FROM ${EmployeeDocumentsModel.tableName} GROUP BY filename
      HAVING COUNT(filename) > 1;`,
        { type: QueryTypes.SELECT },
      );

      // eslint-disable-next-line no-plusplus
      for (let i = 0; i < documents.length; i++) {
        const prefix = Date.now().toString();
        const fileParts = documents[i].filename.split('.');
        const finalname = `${fileParts[0]}-${prefix}.${fileParts[1]}`;
        // eslint-disable-next-line no-await-in-loop
        await queryInterface.sequelize.query(`UPDATE ${EmployeeDocumentsModel.tableName} SET filename='${finalname}' WHERE id=${documents[i].id};`, { transaction });
      }
      // eslint-disable-next-line no-unused-vars
      // const file = await sequelizeClient.query(
      //   `DELETE d1 from ${EmployeeDocumentsModel.tableName} d1 inner join ${EmployeeDocumentsModel.tableName} d2 on d2.id < d1.id and d2.filename = d1.filename and d2.employeeId = d1.employeeId`,
      //   { type: QueryTypes.DELETE },
      // );

      await queryInterface.addConstraint(EmployeeDocumentsModel.tableName, ['employeeId', 'filename'], {
        type: 'unique',
        name: 'composite_employee_filename',
      }, {
        transaction,
      });
      await transaction.commit();
    } catch (err) {
      // eslint-disable-next-line no-console
      console.log(err);
      await transaction.rollback();
      throw err;
    }
    return true;
  },

Answer 1

I think the biggest issue is that each update is waiting on the previous to complete:

for (let i = 0; i < documents.length; i++) {
    // ...
    await queryInterface.sequelize.query(`UPDATE ${EmployeeDocumentsModel.tableName} SET filename='${finalname}' WHERE id=${documents[i].id};`, { transaction });
}

If you change it to:

const promises = [];
for (let i = 0; i < documents.length; i++) {
    // ...
    promises.push(queryInterface.sequelize.query(`UPDATE ${EmployeeDocumentsModel.tableName} SET filename='${finalname}' WHERE id=${documents[i].id};`, { transaction }));
}
await Promise.all(promises);

you should see a big speedup.