Querying MongoDB to retrieve particular elements from an array within a collection

Results collection contains the following data.

_id                 "9FK5k755ueAYdfip3"
    createdAt       Date {Sat Mar 12 2016 19:58:46 GMT+0100 (CET)}
    results         [Object { errorId="uX6byeiuGjRNXTj6s",  error="02/09/15 13:01:29  backu...ox file was not found. ",  time="02/09/15 13:01:29"}, 
                    Object { errorId="uX6byeiuGjRNXTj6s",  error="02/09/15 13:01:29  backu...ox file was not found. ",  time="02/09/15 13:01:29"},
                    Object { errorId="uX6byeiuGjRNXTj6s",  error="02/09/15 13:22:42  backu...ox file was not found. ",  time="02/09/15 13:22:42"}, 
                    432 more...]

    results:

    0   Object { errorId="uX6byeiuGjRNXTj6s",  error="02/09/15 13:01:29  backu...ox file was not found. ",  time="02/09/15 13:01:29"}  
    1   Object { errorId="uX6byeiuGjRNXTj6s",  error="02/09/15 13:01:29  backu...ox file was not found. ",  time="02/09/15 13:01:29"}   
    2   Object { errorId="uX6byeiuGjRNXTj6s",  error="02/09/15 13:22:42  backu...ox file was not found. ",  time="02/09/15 13:22:42"}

    ...

    14    Object { errorId="5vfLjdbaQLgbuCiNZ",  error="02/09/15 16:04:10  backu...minated with an error. ",  time="02/09/15 16:04:10"}   
    15    Object { errorId="5vfLjdbaQLgbuCiNZ",  error="02/09/15 16:04:10  backu...minated with an error. ",  time="02/09/15 16:04:10"}   
    16    Object { errorId="5vfLjdbaQLgbuCiNZ",  error="02/09/15 16:04:10  backu...minated with an error. ",  time="02/09/15 16:04:10"}

    ...

    183    Object { errorId="uX6byeiuGjRNXTj6s",  error="03/13/15 13:36:24  backu...ox file was not found. ",  time="03/13/15 13:36:24"}
    184    Object { errorId="uX6byeiuGjRNXTj6s",  error="03/13/15 13:42:39  backu...ox file was not found. ",  time="03/13/15 13:42:39"} 
    185    Object { errorId="uX6byeiuGjRNXTj6s",  error="03/13/15 13:42:40  backu...ox file was not found. ",  time="03/13/15 13:42:40"}

I am looking for a query that retrieves all documents with a specific errorId within the results arrays.

I have attempted various queries without success.

For example:

    Results.find ({ results: { $elemMatch : { errorId: 'uX6byeiuGjRNXTj6s'}}})
    Results.find ({ results: { $elemMatch : { Key: 'errorId', 'errorId': 'uX6byeiuGjRNXTj6s'}}}).fetch()
    Results.find ({'results.errorId.$' : 'uX6byeiuGjRNXTj6s'}).fetch()

Your assistance would be greatly appreciated.

Thank you!!!

javascriptmongodbmeteor

Answer №1

Give it a shot by using the power of aggregation

Results.aggregate([{$unwind: '$results'},
                   {$match: {'results.errorId': 'uX6byeiuGjRNXTj6s'}}])

Answer №2

To achieve this, you can utilize the $elemMatch operator in MongoDB. While the Mongo documentation does offer some initial examples, in your specific scenario, it's recommended to use:

{ results: { $elemMatch: { errorId: "abc"} } }

If for any reason that doesn't yield the desired results, as indicated in the mongo documentation, an alternate query could be formulated as follows:

{ "results.errorId": "abc" }

Answer №3

When trying to execute queries from the browser console, I received varying results:

    Results.find({ results: { $elemMatch: { errorId: "uX6byeiuGjRNXTj6s"} } }).fetch()
    [Object { _id="9FK5k755ueAYdfip3",  results=[435],  createdAt=Date}]

    Results.find({ results: { $elemMatch: { "results.errorId": "uX6byeiuGjRNXTj6s"} } }).fetch()
    []

    Results.aggregate([{$unwind: '$results'},{$match: {'results.errorId': 'uX6byeiuGjRNXTj6s'}}]).fetch()
    TypeError: Results.aggregate is not a function


    ...gregate([{$unwind: '$results'},{$match: {'results.errorId': 'uX6byeiuGjRNXTj6s'}...

The first query returned all ids instead of just "uX6byeiuGjRNXTj6s". The other two queries did not work. I proceeded to run them directly (using meteor mongo) from the database and obtained the following outcomes.

     db.results.find({ results: { $elemMatch: { errorId: "uX6byeiuGjRNXTj6s"} })
      - returned ALL ids

     db.results.find({ results: { $elemMatch: { "results.errorId": "uX6byeiuGjRNXTj6s"} })
     - returned empty

     meteor:PRIMARY> db.results.aggregate([{$unwind: '$results'},{$match: {'results.errorId': 'uX6byeiuGjRNXTj6s'}}])
    { "_id" : "9FK5k755ueAYdfip3", "results" : { "errorId" : "uX6byeiuGjRNXTj6s", "error" : "02/09/15 13:01:29  backup.swatycomet.lan nsrd Error encountered while re-signing lockbox 'D:\\EMC\\Networker\\nsr\\lockbox\\backup\\clb.lb': The lockbox file was not found. ", "time" : "02/09/15 13:01:29" }, "createdAt" : ISODate("2016-03-12T18:58:46.967Z") }
    ...

The third query yielded the desired results. Subsequently, when attempting to execute that query in my Meteor code:

 console.log(Results.aggregate([{$unwind: '$results'},{$match: {'results.errorId': 'uX6byeiuGjRNXTj6s'}}]));

An error occurred instead of returning the results.

Error message during template helper execution: .errors@http://localhost:3000/app/client/templates/results/results.js?951539bd4f24742e5d7a64530c2463bfe41fde91:33:21 bindDataContext/<@http://localhost:3000/packages/blaze.js?9391df93ba5076c2cfc61ee68724eb79b65f00d9:2986:14

What could be the issue here?

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