MongoDb RegExp on numbers in example query

Question

The example in the node driver shows a simple regular expression used against a number.

collection.find({'a':/[1|2]/})

where collection is

collection.insert([{'a':1}, {'a':2}, {'b':3}]

This fails for me in both the shell and running the example in node.

Here is the example https://github.com/mongodb/node-mongodb-native/blob/1.4/examples/queries.js

I wouldn't expect this to work as regular expressions are for text ... but its in the current examples ... so I figure it must be correct and I'm missing something.. The sample works fine if the values are strings {a : '1'} ... am I missing something or is the sample out of date ...

Neil Lunn · Accepted Answer · 2014-03-24 06:06:10Z

1

You are not missing anything. A $regex operation will only work on strings. Also from the manual

The $regex operator provides regular expression capabilities for pattern matching strings in queries. MongoDB uses Perl compatible regular expressions (i.e. “PCRE.”)

So the highlighted term there is "strings", and that is exactly how things should be.

From the source of this. It is an "odd" example, but should only be treated as an "example". So there is nothing intrinsically "wrong" with the code. It just doesn't return any results. So in that it is arguably still valid. No-one said it was "supposed" to match documents.

If you believe it should be otherwise, feel free to submit a pull request and or a JIRA

answered Mar 24, 2014 at 6:06

Neil Lunn

151k36 gold badges356 silver badges327 bronze badges

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

1 Comment

Pablo Over a year ago

thanks ... its a little more than odd to me as the example crashes trying to use the returned collection length.

Oleg · Accepted Answer · 2014-03-31 06:41:20Z

0

If you need to use regular expression with numbers, you can do it like this:

collection.find({ $where: "/[1|2]/.test(this.a)" })

But keep in mind that, according to the documentation, MongoDB can't use indexes with $where:

$where evaluates JavaScript and cannot take advantage of indexes. Therefore, query performance improves when you express your query using the standard MongoDB operators (e.g., $gt, $in).

edited Mar 31, 2014 at 6:41

answered Mar 24, 2014 at 10:38

Oleg

23.5k10 gold badges72 silver badges87 bronze badges

Collectives™ on Stack Overflow

MongoDb RegExp on numbers in example query

2 Answers 2

1 Comment

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

1 Comment

Comments

Your Answer

Sign up or log in

Post as a guest

Related