How to use $regex in mongodb aggregation query within $match

Question

I am trying to use the $regex within $match, its not returning the matching documents.

db.collection('MyCollection', function (err, collection) {
  collection.aggregate([
    { $match: { 'Code': 'Value_01', 'Field2': { $regex: '/Value_2/g' } } },  
    { $project: {
        _id: 1,
        CodeNumber: '$Code',
        FieldName2: '$Field2'
      }
    }
  ], function (err, Result_doc) {
    console.log(Result_doc);
  }
});

Can anyone tell me where its going wrong or the correct syntax?

I even tried with replacing the

'Field2': { $regex: /Value_2/g }

JohnnyHK · Accepted Answer · 2013-04-27 13:34:57Z

44

As it says in the $regex docs you linked to, the two ways to do this are:

Field2: /Value_2/g

OR

Field2: { $regex: 'Value_2', $options: 'g' }

But I also tried your second attempt of 'Field2': { $regex: /Value_2/g } and that worked as well.

BTW, the g regex option doesn't make sense in this context as you just need one match anyway. Note that it isn't even listed in the $regex docs.

answered Apr 27, 2013 at 13:34

JohnnyHK

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2 Comments

Mythili Over a year ago

$options is not being shown under $match query when I enter $regex:"<value>".

Raphael Over a year ago

Note: the global option is not supported for MongoDB regex operations (source).

Preview · Accepted Answer · 2015-09-14 10:39:45Z

8

I got it working with the following code:

var Value_match = new RegExp('Value_2');

db.collection('MyCollection', function (err, collection) {

  collection.aggregate([
    { $match: { Code: 'Value_01', Field2: { $regex: Value_match } } },  
    { $project: {
        _id: 1,
        CodeNumber: '$Code',
        FieldName2: '$Field2'
      }
    }
  ], function (err, Result_doc) {
    console.log(Result_doc);
  }
});

On pushing the object content to console using console.dir(Value_match) it prints out '/Value_2/'

edited Sep 14, 2015 at 10:39

Preview

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answered Apr 29, 2013 at 5:27

Amol M Kulkarni

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