MongoDB Regex Search on Integer Value

I want to regex search an integer value in MongoDB. Is this possible?

I'm building a CRUD type interface that allows * for wildcards on the various fields. I'm trying to keep the UI consistent for a few fields that are integers.


> db.seDemo.insert({ "example" : 1234 });
> db.seDemo.find({ "example" : 1234 });
{ "_id" : ObjectId("4bfc2bfea2004adae015220a"), "example" : 1234 }
> db.seDemo.find({ "example" : /^123.*/ });

As you can see, I insert an object and I'm able to find it by the value. If I try a simple regex, I can't actually find the object.



If you are wanting to do a pattern match on numbers, the way to do it in mongo is use the $where expression and pass in a pattern match.

> db.test.find({ $where: "/^123.*/.test(this.example)" })
{ "_id" : ObjectId("4bfc3187fec861325f34b132"), "example" : 1234 }

I am not a big fan of using the $where query operator because of the way it evaluates the query expression and the security risk if the query uses user input data.

That being said, the best way to do this is to $project your document and add another computed field which is the string value of your number.

The $toLower and his sibling $toUpper operators respectively convert a string to lowercase and uppercase but have a little unknown feature which is that, they can be use to convert integer to string.

The $match operator returns all those document that match your pattern using the $regex operator.

        { "$project": { 
            "stringifyExample": { "$toLower": "$example" }, 
            "example": 1 
        { "$match": { "stringifyExample": /^123.*/ } }

which yields:

    "_id" : ObjectId("579c668c1c52188b56a235b7"), 
    "example" : 1234,
    "stringifyExample" : "1234"

    "_id" : ObjectId("579c66971c52188b56a235b9"), 
    "example" : 12334,
    "stringifyExample" : "12334"

Now if what you want is retrieve all the document which contain a particular substring, the easier and better way to do this is in the upcoming release of MongoDB (as of this writing) using the $redact operator which allows a $conditional logic processing.$indexOfCP.

    { "$redact": { 
        "$cond": [ 
            { "$gt": [ 
                { "$indexOfCP": [ 
                    { "$toLower": "$example" }, 
                ] }, 
            ] }, 

which produces:

    "_id" : ObjectId("579c668c1c52188b56a235b7"), 
    "example" : 1234 

    "_id" : ObjectId("579c66971c52188b56a235b9"), 
    "example" : 12334 

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