策略子集加载

一些adapter支持过滤策略管理。 This means that the policy loaded by Casbin is a subset of the policy stored in the database based on a given filter. This allows for efficient policy enforcement in large, multi-tenant environments where parsing the entire policy becomes a performance bottleneck.

要使用支持的adapter处理过滤后的策略，只需调用 LoadFilteredPolicy 方法。 过滤器参数的有效格式取决于所用的适配器。 为了防止意外数据丢失，当策略已经加载， SavePolicy 方法会被禁用。

例如，下面的代码片段使用内置的过滤文件adapter和带有域的RBAC模型。 在本例中，过滤器将策略限制为单个域。 除 "domain1" 以外的任何域策略行被忽略：

import (
    "github.com/casbin/casbin/v2"
    fileadapter "github.com/casbin/casbin/v2/persist/file-adapter"
)

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)

//加载策略现在只包含与“domain1”相关的条目。

There is another method that supports the subset loading feature: LoadIncrementalFilteredPolicy. LoadIncrementalFilteredPolicy is similar to LoadFilteredPolicy, but it does not clear the previously loaded policy. It only appends the filtered policy to the existing policy.