javascript - MongoDB filtering string in array

Question

In one of my schemas (called Question) in mongodb, I have an array defined which consists of strings: e.g.

tags = ['6.01', '6.02', '8.01']

I want to be able to filter through the Questions and find any Question which has a tag starting with '6'. So for example, if we have the following Questions and their associated tags:

Question 1:

tags = ['6.01', '6.02', '8.01']

Question 2:

tags = ['9.01', '7.012', '10.11']

Question 3:

tags = ['7.014', '6.UA', '21.012']

The query should return Question 1 and 3 because they each have at least one tag that starts with a '6'

I think I should use regex, something like ^+'6', but I am not sure how to query in mongodb. Any help is appreciated!

question from:https://stackoverflow.com/questions/65850065/mongodb-filtering-string-in-array

Answer 1

db.questions.find({tags: /^6/})

Mind you, this could be pretty slow if your collection is large. You may want to add an index on tags as well to speed this up: db.questions.createIndex({tags: 1}).