Add note about Snowflake 'rely' for query optimization

website/docs/reference/resource-properties/constraints.md

@@ -119,7 +119,7 @@ models:
 
 In transactional databases, it is possible to define "constraints" on the allowed values of certain columns, stricter than just the data type of those values. For example, Postgres supports and enforces all the constraints in the ANSI SQL standard (`not null`, `unique`, `primary key`, `foreign key`), plus a flexible row-level `check` constraint that evaluates to a boolean expression.
 
-Most analytical data platforms support and enforce a `not null` constraint, but they either do not support or do not enforce the rest. It is sometimes still desirable to add an "informational" constraint, knowing it is _not_ enforced, for the purpose of integrating with legacy data catalog or entity-relation diagram tools ([dbt-core#3295](https://github.com/dbt-labs/dbt-core/issues/3295)).
+Most analytical data platforms support and enforce a `not null` constraint, but they either do not support or do not enforce the rest. It is sometimes still desirable to add an "informational" constraint, knowing it is _not_ enforced, for the purpose of integrating with legacy data catalog or entity-relation diagram tools ([dbt-core#3295](https://github.com/dbt-labs/dbt-core/issues/3295)). Some data platforms can optionally use primary or foreign key constraints for query optimization if you specify an additional keyword.
 
 To that end, there are two optional fields you can specify on any filter:
 - `warn_unenforced: False` to skip warning on constraints that are supported, but not enforced, by this data platform. The constraint will be included in templated DDL.
@@ -287,7 +287,7 @@ select
 Snowflake suppports four types of constraints: `unique`, `not null`, `primary key`, and `foreign key`.
 
 It is important to note that only the `not null` (and the `not null` property of `primary key`) are actually checked at present.
-The rest of the constraints are purely metadata, not verified when inserting data.
+The rest of the constraints are purely metadata, not verified when inserting data. Although Snowflake does not validate `unique`, `primary`, or `foreign_key` constraints, you may optionally instruct Snowflake to use them for query optimization by specifying [`rely`](https://docs.snowflake.com/en/user-guide/join-elimination) in the constraint `expression` field.
 
 Currently, Snowflake doesn't support the `check` syntax and dbt will skip the `check` config and raise a warning message if it is set on some models in the dbt project.