unable to use regex in $in operator in mongodb

Question

I am trying to use the regex with $in operator as mentioned in the docs but I am still unable to get the value.

db.users.find({'profile.firstName':{$in:["/justin/i"]}}).count() = 0

but when I used like this

db.users.find({'profile.firstName':{$in:["justin"]}}).count()=1 and

db.users.find({'profile.firstName':{$in:["Justin"]}}).count()=2

Edited Question

seems like I am not clear with the question I will add the code for easy understanding

I am trying to get the list of documents from a query which is case insensitive.I think it better to explain my doubt with code.

Meteor.users.find({'profile.firstName':{$in:[/justin/i,/helen/i]}}).count()

will give documents whose profile.firstName is justin/Justin/JUSTIn/HElen/helen

but my doubt how to give the variable x=["sai","test","jacob",---etc] in place of helen/justin

chridam · Accepted Answer · 2016-04-29 09:34:39Z

39

You need to wrap the elements in the array with the RegExp object i.e.

regex = [new RegExp("sai", "i"), new RegExp("test", "i"),...]

You can use the map() method to map the elements in the array with the RegExp wrappers to a new array that you can then use in the regex query with $in:

var x = ["sai","test","jacob","justin"],
    regex = x.map(function (e) { return new RegExp(e, "i"); });

db.users.find({"profile.firstName": { "$in": regex } });

Using $in can be fairly efficient with small arrays but not so well with huge lists since it will skip around in the index to find the matching documents, or walk through the whole collection if there isn't an index to use.

Besides using the $in with the regular expression, you could use a pipe-delimited regex pattern with the keywords list like this:

var x = ["sai","test","jacob","justin"],
    regex = x.join("|");

db.users.find({
    "profile.firstName": {
        "$regex": regex, 
        "$options": "i"
    } 
}).count;

edited Apr 29, 2016 at 9:34

answered Apr 29, 2016 at 9:11

chridam

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2 Comments

Gangstead Over a year ago

Both $in and piping the regexs into one worked for me, but the combined regex was 10X faster with an array of 11 regexes and searching a collection of 3.4K documents. Time went from 5000ms to 50ms.

HappyNomad Over a year ago

For a left-anchored (starts w/ ^), case-sensitive (no i option) expression, taking the $in approach would use a configured index and thus be optimal, right?

Muhammad Faizan · Accepted Answer · 2016-04-29 09:42:55Z

5

try doing this way

db.users.find({'profile.firstName':{$in:[/justin/i]}}).count() = 0

you are passing regex as string.

Usually You should ask one problem at a time so question remains focused to a specific problem

well You can directly pass it, like this

// Here I am creating regex for all the elements in array
let myRegex = new RegExp(myArray.join('|'), i) 
and then I can pass this regex
db.users.find({'profile.firstName':{$in: myRegex}}).count() = 0

edited Apr 29, 2016 at 9:42

answered Apr 29, 2016 at 7:24

Muhammad Faizan

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3 Comments

Sai Ram Over a year ago

Hey thanks for solution but please check question once as I have added a little more to it.

Sai Ram Over a year ago

but doesn't that make query with case sensitive

Muhammad Faizan Over a year ago

Hahaha Apologize bro, I might have missed the notification, because have been answering quite many question lately

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