Compreensão das políticas de tabela de clean room¶

Clean rooms can implement data policies to control how data can be used by collaborators. These are in addition to any Snowflake table policies set on the underlying tables linked into the clean room.

Each collaborator in a clean room can set policies on their own data. Your policies are enforced only in requests from other users; your policies are not enforced against your own requests. For example, if your join policy allows joins against only column A, other users are restricted to joining on column A, but you can run joins against any of your columns.

As políticas de clean room podem ser definidas usando a API ou UI de clean room.

To implement policy checks, the following must be true:

The data owner must set a policy in their clean room. You can set policies using either the API or the UI. Each policy type is set separately. Clean room natively implements column policies, row policies, and activation policies. Clean room policies are not additive: When you set a clean room policy, all previous values are deleted.

-- Sets a join policy on column HASHED_EMAIL.
CALL samooha_by_snowflake_local_db.provider.set_join_policy(
  'my_provider_cleanroom',
  ['my_db.my_sch.T1:HASHED_EMAIL']);

-- Replaces the previous join policy. Now the only column in the join policy is AGE_BND.
CALL samooha_by_snowflake_local_db.provider.set_join_policy(
  'my_provider_cleanroom',
  ['my_db.my_sch.T1:AGE_BAND']);

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The template must check the policy in the appropriate place in the template. A clean room policy is checked only if it has the appropriate policy filter applied to the column in the template. If you set a clean room policy to protect your data, you should examine the template to confirm that the template is enforcing your policies as you expect. The following template checks whether col1 is allowed by the data owner’s column policy:
```
SELECT
  IDENTIFIER( {{ col1 | column_policy }} )
FROM {{ source_table[0] }} AS c;
```
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The following template does not check whether col1 has a clean room policy:
```
SELECT
  IDENTIFIER( {{ col1 }})
FROM {{ source_table[0] }} AS c;
```
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Clean rooms supports a different template filter for each policy type. However, the semantics of the filter are not checked, only whether the column is in the policy for that filter type. For example, in the following snippet, the join policy is checked for col1, even though the column is not being joined against. If col1 is in the data owner’s join policy, the query can succeed; if col1 is not in the data owner’s join policy, the query will be blocked.
```
SELECT
  IDENTIFIER( {{ col1 | join_policy }})
FROM {{ source_table[0] }} AS c;
```
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Nota

Column policy checks are carried out when the template JinjaSQL is parsed. Queries with wildcards might not be caught using these checks, and discretion should be used when designing an analysis template. If some columns should really never be queried, consider creating a view of your source table that eliminates these sensitive columns, and link in that view instead.

Snowflake policies in clean rooms¶

When you link tables into a clean room, any Snowflake table policies on the source tables are enforced in the linked tables in the clean room, but these policies aren’t necessarily reported by the clean room API or UI. For instance, a Snowflake join policy continues to be enforced in the clean room, but that join policy is not visible by calling consumer.view_provider_join_policy or consumer.view_join_policy. Therefore, you should either remove policies from the underlying linked tables, create equivalent clean room policies (when they exist), or communicate the existence of these policies clearly to your collaborators so that their queries don’t fail or behave unexpectedly («why can’t I join on this column?»).

Any changes to Snowflake policies in the source tables are automatically propagated to the linked views in the clean room.

As políticas de privacidade do Snowflake impedem a criação de uma exibição a partir de uma tabela protegida; portanto, você não pode criar links em tabelas que tenham políticas de privacidade.

Políticas de junção¶

Set a join policy to indicate which columns in your data can be joined on by any template in the clean room. (Snowflake join policies, in contrast, specify which columns must be joined on.) Join policies apply to all templates in the clean room.

A column cannot be in both a join policy and a column policy, but a column can be in both a join policy and an activation policy.

Implementação de uma política de associação¶

Clean room join policies are enforced against a column if the template applies the join_policy or join_and_column_policy filter to the column.

If a template checks a join policy for a column, and the clean room has no join policies set, or the column is not in the join policy, the query will be blocked.

The following code shows how to set join policies as a provider or a consumer. Remember that policies are only enforced against queries run by another account.

-- Set join policies on two columns in a clean room where you are a provider.
CALL samooha_by_snowflake_local_db.provider.set_join_policy(
  'my_provider_cleanroom',
  ['SAMOOHA_SAMPLE_DATABASE.DEMO.CUSTOMERS:HASHED_EMAIL', 'MYDB.MYSCH.EXPOSURES:HASHED_EMAIL']);

-- Set join policies on two columns in a clean room where you are a consumer.
CALL samooha_by_snowflake_local_db.consumer.set_join_policy(
  'my_consumer_cleanroom',
  ['SAMOOHA_SAMPLE_DATABASE.DEMO.CUSTOMERS:HASHED_EMAIL', 'MYDB.MYSCH.EXPOSURES:HASHED_EMAIL']);

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Os procedimentos a seguir são usados para visualizar ou gerenciar políticas de associação no código:

consumer.set_join_policy
consumer.view_provider_join_policy
consumer.view_join_policy
provider.view_join_policy
provider.set_join_policy

Políticas de coluna¶

Set a column policy to indicate which of your columns can be projected in analysis results from a specific template. Column policies are applied to specific templates in a specific clean room.

Uma coluna não pode estar em uma junção e em uma política de coluna. Uma coluna pode estar tanto em uma política de ativação quanto em uma política de coluna.

Implementação de uma política de coluna¶

Clean room column policies are enforced against a column only if the template uses the column_policy or join_and_column_policy filter.

If a clean room checks a column policy for a column, and the column is not in the column policy, or the clean room has no column policies, the query will be blocked.

The following code shows how to set column policies for three columns when accessed by the prod_overlap_analysis template. The example shows how to set the policy both as a provider and a consumer. Remember that policies are only enforced against queries run by another account.

-- Set column policy on prod_overlap_analysis template in a clean room where
-- you are a provider.
call samooha_by_snowflake_local_db.provider.set_column_policy(
  'my_provider_cleanroom',
  ['prod_overlap_analysis:SAMOOHA_SAMPLE_DATABASE.DEMO.CUSTOMERS:STATUS',
   'prod_overlap_analysis:SAMOOHA_SAMPLE_DATABASE.DEMO.CUSTOMERS:AGE_BAND',
   'prod_overlap_analysis:SAMOOHA_SAMPLE_DATABASE.DEMO.CUSTOMERS:DAYS_ACTIVE']);

-- Set column policy on prod_overlap_analysis template in a clean room where
-- you are a consumer.
call samooha_by_snowflake_local_db.consumer.set_column_policy(
  'my_consumer_cleanroom',
  ['prod_overlap_analysis:SAMOOHA_SAMPLE_DATABASE.DEMO.CUSTOMERS:STATUS',
   'prod_overlap_analysis:SAMOOHA_SAMPLE_DATABASE.DEMO.CUSTOMERS:AGE_BAND',
   'prod_overlap_analysis:SAMOOHA_SAMPLE_DATABASE.DEMO.CUSTOMERS:DAYS_ACTIVE']);

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Os procedimentos a seguir são usados para visualizar ou gerenciar políticas de coluna no código:

consumer.set_column_policy
consumer.view_column_policy
consumer.view_provider_column_policy
provider.set_column_policy
provider.view_column_policy

Políticas de ativação¶

Set an activation policy to indicate which of your columns can be activated by an activation template. Activation saves query results to a table in the Snowflake account of the provider or consumer, or to a third-party activation connector.

Uma coluna pode fazer parte de uma política de ativação, bem como de qualquer outra política.

Implementação de uma política de ativação¶

As políticas de ativação podem ser definidas na UI de clean rooms se o modelo permitir a ativação.

Activation policies are set for a specific column in a specific template.

Activation policies are enforced against a column only if the template applies the activation_policy filter to the column.

The following code demonstrates setting an activation policy to allow the HASHED_EMAIL and REGION_CODE columns to be activated in a clean room. This policy affects all users and all activation templates in the clean room. There are equivalent procedures for providers and consumers in a clean room. Call the procedure that reflects your role in the clean room.

-- Set activation policy on prod_overlap_analysis template in a clean room where you are a provider
call samooha_by_snowflake_local_db.provider.set_activation_policy('my_cleanroom', [
    'prod_overlap_analysis:SAMOOHA_SAMPLE_DATABASE.DEMO.CUSTOMERS:HASHED_EMAIL',
    'prod_overlap_analysis:SAMOOHA_SAMPLE_DATABASE.DEMO.CUSTOMERS:REGION_CODE' ]);

-- Set activation policy on prod_overlap_analysis template in a clean room where you are a consumer
call samooha_by_snowflake_local_db.consumer.set_activation_policy('my_cleanroom', [
    'prod_overlap_analysis:SAMOOHA_SAMPLE_DATABASE_NAME.DEMO.CUSTOMERS:HASHED_EMAIL',
    'prod_overlap_analysis:SAMOOHA_SAMPLE_DATABASE_NAME.DEMO.CUSTOMERS:REGION_CODE' ]);

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Os procedimentos a seguir são usados para gerenciar as políticas de ativação no código:

consumer.set_activation_policy
provider.set_activation_policy

Políticas de agregação¶

As políticas de agregação exigem que todas as consultas em uma tabela contenham agregações (GROUP BY, COUNT e outras funções), além de especificar um número mínimo de linhas por grupo de resultados, ou o grupo será omitido dos resultados.

As clean rooms não têm sua própria implementação de políticas de agregação; para aplicar restrições de agregação nos dados vinculados, aplique uma política de agregação na tabela de origem ou implemente restrições de agregação em seu modelo.

Alguns modelos fornecidos pelo Snowflake usam os parâmetros threshold e threshold_value definidos para um usuário ou modelo. Esses valores podem ser modificados na UI de clean rooms, ou chamando provider.add_consumers ou provider/consumer.set_privacy. Se definido para um consumidor, você pode acessar esses valores em seu modelo.