CODEWITHSUNDEEP
node.jsexpresstransactionssequelize.js
user275157
user275157

Reputation: 1352

sequelize transactions in expressjs not executing

Trying to figure out the right way to use Sequelize transactions in expressjs. The following code finds a post by id increments the reply count in the post table, updates the post and then creates a reply in the reply table. Trying to call the code in a controller action and it does not work. The internal promises are not being hit. Any suggestions on the right way to use the transactions in Sequelize? 

Sequelize.transaction(function (t) {  
db.Post.find({where:{id: postId}}, {transaction:t}).then(function(post)
{
  var count = post.reply + 1; 
  post.update({replyCount:count},{transaction:t});
  db.Reply.create(replyData, {transaction:t}).then(function(newcomment, created){      
          res.json(newcomment);

      });     
});
  }).then(function (result) {
// Transaction has been committed
// result is whatever the result of the promise chain returned to the transaction callback 
 }).catch(function (err) {
// Transaction has been rolled back
// err is whatever rejected the promise chain returned to the transaction 
});        
});

Upvotes: 2

Views: 910

Answers (2)

DeeZone
DeeZone

Reputation: 830

There's no value in the initial .find() being in the transaction. There's nothing to undo in the case of a rollback. Only writes or updates need to be rolled back in a transaction. The try/catch will deal with any of the queries failing and a rollback will be automatically triggered for the transaction items.

Consider this more modern ES6 solution:

try {

  const result = await sequelize.transaction(async (t) => {

    // no need to include this in the transaction, it only reads (find)
    const post = await db.Post.find({where:{id: postId}});

    const count = post.reply + 1;
    const updateResult = await post.update({
      replyCount: count
    }, { transaction: t });

    // i guess you want to use result in here to create replyData
    const createResult = await db.Reply.create({
      replyData,
    }, { transaction:t });

    return res.json(newcomment);
  });

} catch (error) {

  // If the execution reaches this line, an error occurred.
  // The transaction has already been rolled back automatically by Sequelize!

}

Reference: - https://sequelize.org/master/manual/transactions.html#managed-transactions

Upvotes: 0

feiiiiii
feiiiiii

Reputation: 1593

Sequelize.transaction(function (t) {  
 return db.Post.find({where:{id: postId}}, {transaction:t}).then(function(post)
{
  var count = post.reply + 1; 
  return post.update({replyCount:count},{transaction:t})
         .success(result =>
              // i guess you want to use result in here to create replyData
              return db.Reply.create(replyData, {transaction:t})

                     .then(function(newcomment, created){      
                           return res.json(newcomment);

                      }); 
         );

});

Upvotes: 2

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