Custom Materialization with unique_key

Use Case - incrementally load data into Snowflake with dbt.
Now , i saw this article which solves/answers my question. However, i am stuck at point, need help for the same.
I have already gone through this awesome article here
The part i need help is “file with different name have data which is already present in the the table”. What to do or changes, if needed in the macro mentioned in the above article should be done?
I can think of using unique_key in conjunction with custom materialization, but i haven’t tried it yet, want to know experts opinions before going ahead with the solution.

P.S - This is my first dbt project :slight_smile:
Appreciate your help