| --- |
| id: policy-subset-loading |
| title: Policy Subset Loading |
| --- |
| |
| Some adapters support filtered policy management. This means that the policy loaded by Casbin is a subset of the policy in storage based on a given filter. This allows for efficient policy enforcement in large, multi-tenant environments when parsing the entire policy becomes a performance bottleneck. |
| |
| To use filtered policies with a supported adapter, simply call the `LoadFilteredPolicy` method. The valid format for the filter parameter depends on the adapter used. To prevent accidental data loss, the `SavePolicy` method is disabled when a filtered policy is loaded. |
| |
| For example, the following code snippet uses the built-in filtered file adapter and the RBAC model with domains. In this case, the filter limits the policy to a single domain. Any policy lines for domains other than `"domain1"` are omitted from the loaded policy: |
| |
| ```go |
| import "github.com/casbin/casbin" |
| |
| enforcer := casbin.NewEnforcer() |
| |
| adapter := fileadapter.NewFilteredAdapter("examples/rbac_with_domains_policy.csv") |
| enforcer.InitWithAdapter("examples/rbac_with_domains_model.conf", adapter) |
| |
| filter := &fileadapter.Filter{ |
| P: []string{"", "domain1"}, |
| G: []string{"", "", "domain1"}, |
| } |
| enforcer.LoadFilteredPolicy(filter) |
| |
| // The loaded policy now only contains the entries pertaining to "domain1". |
| ``` |
