Add Redshift behavior change: restrict_direct_pg_catalog_access (#6082)

website/docs/reference/global-configs/behavior-changes.md

@@ -61,6 +61,7 @@ When we use dbt Cloud in the following table, we're referring to accounts that h
 | require_explicit_package_overrides_for_builtin_materializations | 2024.04.141      | 2024.06.192         | 1.6.14, 1.7.14  | 1.8.0             |
 | require_resource_names_without_spaces                           | 2024.05.146      | TBD*                | 1.8.0           | 1.9.0             |
 | source_freshness_run_project_hooks                              | 2024.03.61       | TBD*                | 1.8.0           | 1.9.0             |
+| [Redshift] restrict_direct_pg_catalog_access                    | 2024.09.242      | TBD*                | dbt-redshift v1.9.0           | 1.9.0             |
 
 When the dbt Cloud Maturity is "TBD," it means we have not yet determined the exact date when these flags' default values will change. Affected users will see deprecation warnings in the meantime, and they will receive emails providing advance warning ahead of the maturity date. In the meantime, if you are seeing a deprecation warning, you can either:
 - Migrate your project to support the new behavior, and then set the flag to `True` to stop seeing the warnings.
@@ -121,3 +122,11 @@ on-run-start:
   - '{{ ... if flags.WHICH != 'freshness' }}'
 ```
 </File>
+
+## Adapter-specific behavior changes
+Some adapters may show behavior changes when certain flags are enabled. Refer to the following sections for each respective adapter.
+### [Redshift] restrict_direct_pg_catalog_access
+
+Originally, the `dbt-redshift` adapter was built on top of the `dbt-postgres` adapter and used Postgres tables for metadata access. With this flag enabled, the adapter will use the Redshift API (through the Python client) if available, or query Redshift's `information_schema` tables instead of using `pg_` tables.
+
+While we don't expect any user-noticeable behavior changes due to this change, out of caution we are gating it behind a behavior-change flag and encouraging users to test it before it becomes the default for everyone.