MongoDB text index wildcard weight - mongodb

Question

Suppose I have sample db structure
[
{ name: 'hello world', description: { key: 'something' } },
{ name: 'user', description: { key: 'hello world' } },
]
with index
db.fulltext.createIndex({ name: 'text', '$**': 'text' }, { weights: { name: 10, '$**': 5 } })
I am finding documents with the query
db.fulltext.find({ $text: { $search: 'hello world' } }, { score: { $meta: 'textScore' } })
But... It gives me 15.0 score for both documents... It's impossible to add weight to wildcard operator? Why second document multiply score from name key?

Answer 1

The wildcard index "$**" includes all the string fields in the document in the text index. In the above scenario, name is a string attribute for which weight was given as 10 and in general all string fields weight was assigned as 5 (including name field because wild card is used). So, the weight is overridden.
When the text search is done, equal weightage is given for all String fields. So, the score is same for both the documents as there is no relative significance to the other indexed fields (i.e. because the wild card was used while creating the index).
The $text operator assigns a score to each document that contains the
search term in the indexed fields. The score represents the relevance
of a document to a given text search query.
When different weight is need for different fields, you need to provide the field names specifically while creating the index. In other words, you should not provide a weight for a String field and include wild card weight for all string fields. Obviously, one weight will override the other.
If you can change the index as mentioned below, you can see the difference.
Create Index:-
db.fulltext.createIndex({ name: 'text', 'description.key' : 'text' }, { weights: { name: 10, 'description.key' : 5 } })
Search:-
db.fulltext.find({ $text: { $search: 'hello world' } }, { score: { $meta: 'textScore' } })
Result:-
{
"_id" : ObjectId("57e119cbf522cc85b5595797"),
"name" : "hello world",
"description" : {
"key" : "something"
},
"score" : 15
}
{
"_id" : ObjectId("57e119cbf522cc85b5595798"),
"name" : "user",
"description" : {
"key" : "hello world"
},
"score" : 7.5
}