does a full refresh enforce an incremental model unique key?

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1

Hey all!

very simple question:

when you trigger a full refresh on an incremental model, is the unique key constraint of uniqueness and non-null still enforced? Only thing I found in the doc is full refresh treats your model like a regular table, so I wasn’t sure of the behavior.

Thanks!

2

dbt does not verify the uniqueness of the fields listed in the unique_key config. If you want to verify that it’s actually unique, use a <Add data tests to your DAG | dbt Developer Hub test> or a <Model contracts | dbt Developer Hub model constraint> (but unique constraints are only enforced on Postgres currently)

The unique_key config for an incremental model just tells dbt what fields to join on for a merge operation. https://docs.getdbt.com/docs/build/incremental-models#defining-a-unique-key-optional

Note: @Owen originally posted this reply in Slack. It might not have transferred perfectly.

3

Okay thanks! So I can add a data_test that would verify for uniqueness, but I wouldn’t need one for not_null since that one is handled by the incremental model, correct?

4

I don’t know that the unique_key config implies any runtime constraints (unique, non-null). As far as I know, you need to validate such things yourself. Although most database platforms support enforcing non-null constraints via dbt model contracts.

Note: @Owen originally posted this reply in Slack. It might not have transferred perfectly.

5

For the incremental, it fails if the unique keys contains nulls. That part is written in the docs