Cannot return array if item not present in dynamodb

Question

I have a function that will take an array of jobs as a parameter in it. This function will check the existence of each job in the database through its id.

If a job is not to present in the database, that particular job needs to be pushed into an array called latestJobs. I'm calling this function in my main.js file. But the code breaks and stops.

Below is my main.js code:

module.exports.app = async () => {
 try {
    ...
    const jobs = await getJobsForCountries(body);
    const latestJobs = await filterPreDraftedJobs(jobs);
    console.log('latestJobs', latestJobs);

  } catch (e) {
    console.error('Error:- ', e); // Comes to here
  }
};

My checker function looks like:

module.exports = async (jobs) => {
  let latestJobs = [];
  for (const job of jobs) {
    const params = {
      TableName: process.env.DYNAMODB_TABLE,
      Key: {
        id: job.Id
      }
    };
    await dynamoDb.get(params, (err, data) => {
      if (err) {
        latestJobs.push(job);
        console.log('Job not found in DB'); 
      }
    }).promise();
  }
  return latestJobs;
};

How can I fix this issue? I want the latestJobs which will not present in the database. Is there a function for dynamodb which can do this for me?

@preethiR ??? :D . I don't think so, I think you do not have any table with name is process.env.DYNAMODB_TABLE on your system. dynamoDb.get always return success if item with id value is job.Id existed or not. In not found case, you can check data.Item === null. — hoangdv
– hoangdv, Commented Jan 22, 2020 at 1:19

Yashwardhan Pauranik · Accepted Answer · 2020-01-21 11:57:24Z

1

You are mixing callback, promise and await style. I would do it like this

module.exports = async (jobs) => {
  let latestJobs = [];
  for (const job of jobs) {
    const params = {
      TableName: process.env.DYNAMODB_TABLE,
      Key: {
        id: job.Id
      }
    };
    try {
      const result = await dynamoDb.get(params).promise();
      if (result) {
       return; 
      }
    } catch(err) {
      latestJobs.push(job);
    }
  }
  return latestJobs;
};

Also, make sure that table is created and the region and name you are passing is correct.

edited Jan 21, 2020 at 11:57

Yashwardhan Pauranik

5,5865 gold badges45 silver badges78 bronze badges

answered Jan 21, 2020 at 11:27

Ashish Modi

7,7902 gold badges23 silver badges36 bronze badges

Sign up to request clarification or add additional context in comments.

10 Comments

Yashwardhan Pauranik Over a year ago

I have changed my code as you have suggested. But the control flow never goes inside if(!result) block. Instead it is going into catch block.

Yashwardhan Pauranik Over a year ago

I figured it out. I have just moved the latestJobs.push(job) inside .catch block. And now it is working.

Ashish Modi Over a year ago

@YashwardhanPauranik glad it worked. by the way what is the error you are getting in catch?

Sohan Over a year ago

Why can't you write clean and module function to handle this, the code above looks unhealthy

hoangdv Over a year ago

@YashwardhanPauranik This mean latestJobs.push(job); always be call, although item is existed or not ???

|

Sohan · Accepted Answer · 2020-01-23 10:09:50Z

0

I am not much familiar with dynamoDB but looking at the above conversation code must be something like this. I have tried to improve performance and making sure the code is modular and readable.

async function addUpdateJobs(jobs)
{
    let paramsArray = [];
    for (const job of jobs)
    {
        const jobParams = {
        params:{
            TableName: process.env.DYNAMODB_TABLE,
            Key: {
                id: job.Id
            }               
        },
         job:job
    };
        paramsArray.push(jobParams );

    }
    return await this.getJobs(paramsArray);
}


function getJobs(paramsArray)
{
    let latestJobs = [];
    paramsArray.each(async (jobParam)=>
    {
        try
        {
            const result = await dynamoDb.get(jobParam.params).promise();
            if (result)
            {
                return;
            }
        } catch (err)
        {
            latestJobs.push(jobParam.job);
        }
    });
    return latestJobs;

}

PS: Also I was gonig through error handling in amazondynamodb.

edited Jan 23, 2020 at 10:09

answered Jan 22, 2020 at 6:02

Sohan

6,8796 gold badges40 silver badges59 bronze badges

6 Comments

Yashwardhan Pauranik Over a year ago

The above code is modular, but when I split I have to run 2 loops instead of one.

Sohan Over a year ago

Look at this way, within a loop every time you are trying to do some expensive operation and other jobs are waiting. Why not iterate over loop of params we need? Initial loop we are iterating will have no performance impact. Code looks clean and neat. More important is, it is human readable.

Yashwardhan Pauranik Over a year ago

There will be no` job` instance in the catch block

Sohan Over a year ago

If job is not found you get the error right, and param include the ` id: job.Id` right?

Yashwardhan Pauranik Over a year ago

The variable job is not present in the getJobs() where it is being pushed. Hence wil throw error.

|

Collectives™ on Stack Overflow

Cannot return array if item not present in dynamodb

2 Answers 2

10 Comments

6 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

10 Comments

6 Comments

Your Answer

Sign up or log in

Post as a guest

Related