title: Best way to implement case-insensitive queries in MongoDB
body: <p>What is the best way to implement case-insensitive queries in MongoDB?</p>
  
  <p>For example, 
  A database has a collection of contacts with a first name field.
  One document has 'Adam' in the first name field, another has 'adam'.
  What is the best way to query for documents with the first name = 'adam', regardless of the case?</p>