Datafold supports composite primary keys, meaning that you can assign multiple columns that make up the primary key together.

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Metadata

The first option is setting the primary-key key in the dbt metadata. There are several ways to configure this in your dbt project using either the meta key in a yaml file or a model-specific config block. 
models:
  - name: users
    columns:
      - name: user_id
        meta:
          primary-key: true
    ## for compound primary keys, set all parts of the key as a primary-key ##
    # - name: company_id
    #   meta:
    #     primary-key: true

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Tags

If the primary key is not found in the metadata, it will go through the tags. 
models:
  - name: users
    columns:
      - name: user_id
        tags:
          - primary-key
    ## for compound primary keys, tag all parts of the key ##
    # - name: company_id
    #   tags:
    #       - primary-key

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Inferred

If the primary key isn’t provided explicitly, Datafold will try to infer a primary key from dbt’s uniqueness tests. If you have a single column uniqueness test defined, it will use this column as the PK. 
models:
  - name: users
    columns:
      - name: user_id
        tests:
          - unique
Also, model-level uniqueness tests can be used for inferring the PK. 
models:
  - name: sales
    columns:
      - name: col1
      - name: col2
      ...
    tests:
      - unique:
          column_name: "col1 || col2"
          # or
          column_name: "CONCAT(col1, col2)"
      # we also support dbt_utils unique_combination_of_columns test
      - dbt_utils.unique_combination_of_columns:
          combination_of_columns:
            - order_no
            - order_line
Keep in mind that this is a failover mechanism. If you change the uniqueness test, this will also impact the way Datafold performs the diff.