[TuringNYC]

Our most shocking discovery on Redshift was that primary key constraints are not honored. (Not sure why they even have PK identifiers given this, it just adds more confusion.)

[jw887c]

This is the case for most column oriented data warehouses (including BigQuery, but Snowflake does allow for 1 PK). It's just the nature of the technology.

[dits59]

Suppose you are using AWS Datapipeline, it will make use of PK to get rid of duplicates.