如何使用promise对节点js中的许多mysql查询进行事务操作？

Question

I have 27 mysql update queries on a single table. All these queries are to be run in a transaction mode, like if one operation fails all other updated queries should rollback.

How I will implement this nodejs with promises?

Answer 1

I'm assuming you use mysql driver found here .

According to documentation , this drivers natively supports transactions like this (copied from documentation):

connection.beginTransaction(function(err) {
  if (err) { throw err; }
  connection.query('INSERT INTO posts SET title=?', title, function (error, results, fields) {
    if (error) {
      return connection.rollback(function() {
        throw error;
      });
    }

    connection.query('INSERT INTO log SET data=?', log, function (error, results, fields) {
      if (error) {
        return connection.rollback(function() {
          throw error;
        });
      }
      connection.commit(function(err) {
        if (err) {
          return connection.rollback(function() {
            throw err;
          });
        }
        console.log('success!');
      });
    });
  });
});

Since you mentioned promises, you would want to use promise-mysql package which wraps mysql calls in Bluebird promises.

Answer 2

You can use below approach to handle your secnario.

• Create an array of queries which needs to be run. In below example I have created queries and their placeholder values and passed them as an array of objects
• return a promise to caller which gets resolved when all queries supposed to be run inside a transaction finished
• start the transaction
• run queries one by one inside transaction block
• store the result inside an accumulator as soon as query returns result
• if all transactions are complete the commit the transaction and return accumulated result to caller
• otherwise rollback the transaction and return the error to caller via promise

Below is the approach which I have mentioned -

 function executeTransaction(queries) { try { const connection = yield getConnectionObj({/* your db params to get connection */) let results = [] return new Promise(function(resolve, reject) { connection.beginTransaction(function (err) { if (err) throw err console.log("Starting transaction") queries .reduce(function (sequence, queryToRun) { return sequence.then(function () { parent.query(queryToRun.query, queryToRun.values) /* pass your query and connection to a helper function and execute query there */ return queryConnection( connection, query, queryParams, ).then(function (res) { /* Accumulate resposes of all queries */ results = results.concat(res) }) }).catch(function (error) { reject(error) }) }, Promise.resolve()) .then(function () { connection.commit(function (err) { if (err) { /* rollback in case of any error */ connection.rollback(function () { throw err }) } console.log('Transactions were completed!') /* release connection */ connection.release() /* resolve promise with all results */ resolve({ results }) }) }) .catch(function (err) { console.log('Transaction failed!') connection.rollback(function () { console.log('Abort Transaction !!!') throw err }) }) }) }) /* End Transaction */ } catch (error) { return Promise.reject(error) } }