title: How do I exactly use the mongodb partialFilterExpression in my node application?
body: <p>I am using nodejs, mongodb as my data base and mongoose. I wanted to use partialFilterExpression to handle issue with mongodb saving null as unique value when I set unique to be true and a user provides an empty value for that object.</p>
  <p>I am using mongodb Atlas. I didn't install mongodb in my local machine. Methods that I have seen online on how to use partialFilterExpression didn't explain if it is possible for developers who are using mongodb Atlas. I have tried using it inside my mongoose schema but it didn't work.</p>
  <p>Can partialFilterExpression be used inside mongoose schema? If no, how can I use it with my mongodb Atlas database system?
  Thanks</p>