Map reduce mongodb javascript IGNORE NULL values in this

Question

I'm not sure how, but I'd like to continue on when this.tag_list is null

var mapFunc3 = function(){
   var tags = this.tag_list.split(',');
   for (i in tags) {
     emit(tags[i], 1);
   }
}

var reducFunc3 = function(key, values){
    var count = 0;
    for( i in values){
      count += values[i];
    }
    return count;
}

db.names.mapReduce(
    mapFunc3,
    reducFunc3,
    {out: "mr_3"}
)

The error I get is:

"errmsg" : "MapReduce internal error :: caused by :: TypeError: this.tag_list is null :\n@:2:5\n",
        "code" : 139,
        "codeName" : "JSInterpreterFailure"
}

Make mapFunc3 as arrow function and try.

Sarun UK
– Sarun UK

2020-10-22 15:42:00 +00:00
Commented Oct 22, 2020 at 15:42 — Sarun UK
– Sarun UK, Commented Oct 22, 2020 at 15:42

diam · Accepted Answer · 2020-10-23 05:19:59Z

1

So instead of changing the JavaScript, I changed the Mongodb query so that it did not map any null items:

db.names.mapReduce(
mapFunc3,
reducFunc3,
{
out: {merge: "mr_3"},
query: {"tag_list": {$ne: null}}
}
)

answered Oct 23, 2020 at 5:19

diam

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