Unique index in mongoDB 3.2 ignoring null values

Question

I want to add the unique index to a field ignoring null values in the unique indexed field and ignoring the documents that are filtered based on partialFilterExpression.

Answer 1

You can create partial index in mongo:3.2. Example, if ipaddress can be "", but "127.0.0.1" should be unique. The solution can be like this:

db.collectionName.createIndex(
 {"ipaddress":1},
 {"unique":true, "partialIndexExpression":{"ipaddress":{"$gt":""}}})

This will ignore "" values in ipaddress filed and still be unique