presto-hive/src/main/java/io/prestosql/plugin/hive/metastore/cache/CachingHiveMetastore.java/CachingHiveMetastore/updateIdentity
class CachingHiveMetastore:    private HiveIdentity updateIdentity(HiveIdentity identity)
    {
        // remove identity if not doing impersonation
        return delegate.isImpersonationEnabled() ? identity : HiveIdentity.none();
    }