lighting should support auto detecting data duplication

[glorv]

Feature Request

Describe your feature request related problem:

Lightning should support auto-detecting data duplication.

Describe the feature you'd like:

Following #1109, lightning should support detecting data duplication with one table.

Describe alternatives you've considered:

Teachability, Documentation, Adoption, Migration Strategy:

[tisonkun]

How do we define "data duplication"? Is there a glossary explanation or dev docs?

I'm unsure what is considered "duplicated data" in lightning world and a link to a document talking about it or a brief explanation is desirable.