mongodb Push values into array variable

Question

I am writing a cleansing function which will delete all invalid docs from collection. For this I have an idea to push invalid _id values into array variable and delete with $in.

function(scan){
var err
for(var n=1;n<scan;n++){
var doc = db.zeroDimFacts.findOne({_id:n}) ,nKeys =0; 
for(k in doc)
    nKeys++
if(nKeys <5)
    err = n.toArray()
}

After I push all values to err Array, I have a script to delete matching docs. However, there is something missing with the code which throws me error at n.toArray() .
Can someone help me to correct the code?

as mentioned in the problem statement, criteria is to delete the invalid docs. — N Raghu
– N Raghu, Commented Jul 14, 2016 at 8:13
Not clear what is an invalid doc. If you explain it someone can help you do it in a criteria. — Amiram Korach
– Amiram Korach, Commented Jul 14, 2016 at 8:29
Hi Sherin, If you are asking how I assume a doc as invalid, it a simple check to count the number of keys, whereas it should be 5 in my case, if the keys are less then it fails in the criteria. — N Raghu
– N Raghu, Commented Jul 14, 2016 at 8:32
For this scope, a doc is considered as invalid if the keys are less than 5. If you see the code, I am trying to insert the _id values of docs which are having less than 5 keys. In short, I don't want to immediately delete a doc if it is invalid, I want to push all the values into array and then delete in go at the end. — N Raghu
– N Raghu, Commented Jul 14, 2016 at 8:35

Andriy Simonov · Accepted Answer · 2016-07-14 11:35:06Z

1

function(scan) {
    var doc;
    var nKeys;
    var err = [];

    for(var n = 1; n < scan; ++ n) {
        doc = db.zeroDimFacts.findOne({_id: n})
        nKeys = 0;

        for(k in doc) {
            ++ nKeys;
        }
        if(nKeys < 5) {
            err.push(n);
        }
    }
    return err;
};

Pay attention to findOne() call. When it returns null, n will get into the array which seems undesirable to me.

answered Jul 14, 2016 at 11:35

Andriy Simonov

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Comments

npr · Accepted Answer · 2016-07-14 08:02:54Z

1

You can use findByIdAndRemove({criteria}) and depending on return value you can have the logic.

answered Jul 14, 2016 at 8:02

npr

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8 Comments

N Raghu Over a year ago

Hi, I am not working on mongoose, I am writing a function inside mongodb.

npr Over a year ago

Will findOneAndDelete help : docs.mongodb.com/manual/reference/method/…

N Raghu Over a year ago

I'm not sure on this, it may help in general scenario because it validates and delete the document in very successful iteration, it would take a longer time for a collection having millions of docs. This is the reason why I have opted to first collect all the id of invalid docs and then input to delete them in one go.

npr Over a year ago

Inserting in a bulk way is faster because before insertion all your docs are in memory and they are inserted to db->storage. But in delete case they are in db already - you can use db.collection.remove with some criteria. Collecting all ids and deleting them as you have explained might not be the solution you are looking for.

npr Over a year ago

Also have a look at this - if it helps: stackoverflow.com/questions/28788841/…

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