preserve null and empty arrays mongodb code example

Example 1: mongodb empty an array field

db.collection.update({}, { $set : {'myArray': [] }} , {multi:true} )

Example 2: mongodb unwind

{
  $unwind:
    {
      path: <field path>,
      includeArrayIndex: <string>,
      // to include documents whose sizes field is null, missing, or an empty array.
      preserveNullAndEmptyArrays: <boolean>
    }
}