MongoDB query $in with regex array of element

问题:

Ok i am trying to implement a query, which is trying to perform regex search ( which contains an array list ) on a bunch of document

Its hard for me to explain...so I am basically coming to direct point.

There is query which works with regex array...

db.paper.find({"category": {$in: [ /xd/, /sd/, /ad/ ] }})

There is query which doesn't works with regex array...

db.paper.find({"category": {$in: [ "/xd/", "/sd/", "/ad/" ] }})

So basically what I want is remove "" sign from string array...so that i can perform below query..

var sea = [ "/xd/", "/sd/", "/ad/" ];
db.paper.find({"category": {$in: sea }});

回答1:

it does not work when the double quotes are present because they are interpreted as strings instead of as RegExp objects. So to make it to work, you have to convert it to RegExp objects first in Javascript like this.

var sea = [ "xd", "sd", "ad" ]; // Note: no slashes
var regex = [];
for (var i = 0; i < sea.length; i++) {
    regex[i] = new RegExp(sea[i]);
}
db.paper.find({"category": {$in: regex}});

Remember, MongoDB shell uses Javascript

回答2:

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:

Test documents:

db.papertest.insert([
    { category: "ad bd cd" },
    { category: "dd ed fd" },
    { category: "gd hd id" },
    { category: "jd kd ld" },
    { category: "md nd od" },
    { category: "pd qd rd" },
    { category: "sd td ud" },
    { category: "vd wd xd yd zd" },
]);

The magic:

var keywords = ["xd", "sd", "ad"],
    regex = keywords.join("|");

db.papertest.find({
    "category": {
        "$regex": regex, 
        "$options": "i"
    } 
});

The results

{ "_id" : ObjectId("56bb6f171bb4f693057c0ba4"), "category" : "ad bd cd" }
{ "_id" : ObjectId("56bb6f171bb4f693057c0baa"), "category" : "sd td ud" }
{ "_id" : ObjectId("56bb6f171bb4f693057c0bab"), "category" : "vd wd xd yd zd" }

回答3:

For this you can add a regular expression to each item in the array, you can do it in the following way.

data = ['hoLA','Que','TAL', 'Nueva'];
data  = data.map(function(v, i){return new RegExp(v, 'i')});
MyCollection.find({"thing": {$in : data}}, function(err, data){
    if (err) {
        console.log(err)
    }else{
        data.forEach(function(item){
            console.log(item.nombre);
        })
    }
});

回答4:

Here is simple way to transform /.*/ style regex.

var sea = [ "/xd/", "/sd/", "/ad/" ];

var rx = [];
sea.forEach(function name(value) {
    var v = value.replace(/\//ig,"");
    rx.push(new RegExp(v));
});

db.paper.find({"category": {$in: rx}});