5.5 Oracle Data Redaction Policies on Materialized Views
You can create Oracle Data Redaction policies on materialized views and on their base tables.
However, ensure that the creator of the materialized view, or the user who performs the refresh of the materialized view, is not blocked by any Data Redaction policies. In other words, the user performing the materialized view creation or refresh operations should be exempt from the Data Redaction policy. When a materialized view is created based on a redacted table, the actual data is copied, but the underlying table's redaction policy is not transferred to the materialized view. To protect the materialized view, a separate redaction policy is required as the underlying table's redaction policy will not apply.
As a best practice, when you create a new materalized view, treat it as a copy of the actual table, and then create a separate Data Redaction policy to protect it.
Oracle Data Warehouse Query Rewrite Operation
Query rewrite may rewrite the query to use a materialized view instead of accessing the detail relations, but only if it can guarantee to deliver exactly the same results as if the rewrite had not occurred. Specifically, the query rewrite must retain and respect any Oracle Data Redaction policies against the relations that are specified in the request query. However, any Oracle Data Redaction policies against the materialized view itself do not have any effect when the materialized view is accessed during query rewrite. This is because the data is already protected by the Oracle Data Redaction policies against the relations in the request query.