Mongo regex with array of elements not accurate

Question

Document schema is as follows "events": [ { "title": "title1" }, { "title": "title2" }, { "title": "title3" } ]

I have requirement to search (regex ) in events.title field and get the only matching element/object from the array . For that i am querying like this ,

db.collection.find({ "$or" : [ { "events.title" : { "$regex" : ".*title2.*" , "$options" : "i"}} , { "events.title" : { "$regex" : ".*title5.*" , "$options" : "i"}}] , "events" : { "$elemMatch" : { "title" : { "$ne" :  null }}}},{"events.$":1,"_id":0});

I was expecting the result would be { "events" : [ { "title" : "title2"} ] } , but it returns

{ "events" : [ { "title" : "title1"} ] }

How can i update the query so that only matching element in array is returned in result ?

UPDATE

"events": {
        $elemMatch: {
            "$or": [{
                "title": {
                    "$regex": ".*title2.*",
                    "$options": "i"
                }
            },
            {
                "title": {
                    "$regex": ".*title5.*",
                    "$options": "i"
                }
            }]
        }
    }

did the trick . Now it returns only matching element in the array irrespective of the position.

Thanks for the help

The $ means the first element. You can do it with aggregation maybe but you can filter them after you get the result. — Amiram Korach
– Amiram Korach, Commented Nov 1, 2016 at 8:30
@AmiramKorach If there is no other solution i can filter the result again using drivers . — Mohammed shebin
– Mohammed shebin, Commented Nov 1, 2016 at 9:01

Andriy Simonov · Accepted Answer · 2016-11-01 08:29:52Z

1

Try this

db.collection.find({events: {
                             $elemMatch: {
                                          title: {$in: [/.*title2.*/i,
                                                        /.*title5.*/i]
                                                 }
                                         }
                            }
                   },
                   {"events.$": 1, _id: 0});

answered Nov 1, 2016 at 8:29

Andriy Simonov

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5 Comments

Amiram Korach Over a year ago

This will still give him the first item. $ means first.

Andriy Simonov Over a year ago

That's right, it gives him the first item that matches the regex.

Mohammed shebin Over a year ago

@AndriySimonov this still gives the first element . Is there any other way ?

Andriy Simonov Over a year ago

@Mohammedshebin The question said the only matching element/object from the array. The query returns documents with the first matching array element. It looks exactly as you mentioned in the expected result. I assumed you need only one element. Do you actually need all matching array elements?

Mohammed shebin Over a year ago

"events": { $elemMatch: { "$or": [{ "title": { "$regex": ".*title2.*", "$options": "i" } }, { "title": { "$regex": ".*title5.*", "$options": "i" } }] } } This in projection did the trick . Thanks for the help

Mohammed shebin · Accepted Answer · 2016-11-02 09:31:56Z

0

{"events": {
        $elemMatch: {
            "$or": [{
                "title": {
                    "$regex": ".*title2.*",
                    "$options": "i"
                }
            },
            {
                "title": {
                    "$regex": ".*title5.*",
                    "$options": "i"
                }
            }]
        }
    }
}

in projection did the trick . Now it returns only matching element in the array irrespective of the position

edited Nov 2, 2016 at 9:31

answered Nov 1, 2016 at 9:39

Mohammed shebin

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