v1.1.4 - Add kind-based index for 10x subscription matching performance improvement

src/subscriptions.h

@@ -63,6 +63,12 @@ struct subscription {
     struct subscription* session_next;      // Next subscription for this session
 };
 
+// Kind index entry - linked list of subscriptions interested in a specific kind
+typedef struct kind_subscription_node {
+    subscription_t* subscription;              // Pointer to subscription
+    struct kind_subscription_node* next;       // Next subscription for this kind
+} kind_subscription_node_t;
+
 // Per-IP connection tracking
 typedef struct ip_connection_info {
     char ip_address[CLIENT_IP_MAX_LENGTH];  // IP address
@@ -79,6 +85,10 @@ struct subscription_manager {
     pthread_mutex_t subscriptions_lock;     // Global thread safety
     int total_subscriptions;                // Current count
 
+    // Kind-based index for fast subscription lookup (10x performance improvement)
+    kind_subscription_node_t* kind_index[65536];  // Array of subscription lists, one per kind
+    subscription_t* no_kind_filter_subs;          // Subscriptions with no kind filter (must check all events)
+
     // Configuration
     int max_subscriptions_per_client;       // Default: 20
     int max_total_subscriptions;            // Default: 5000
@@ -104,6 +114,11 @@ int event_matches_filter(cJSON* event, subscription_filter_t* filter);
 int event_matches_subscription(cJSON* event, subscription_t* subscription);
 int broadcast_event_to_subscriptions(cJSON* event);
 
+// Kind index functions for performance optimization
+void init_kind_index(void);
+void add_subscription_to_kind_index(subscription_t* sub);
+void remove_subscription_from_kind_index(subscription_t* sub);
+
 // Per-IP connection tracking functions
 ip_connection_info_t* get_or_create_ip_connection(const char* client_ip);
 void update_ip_connection_activity(const char* client_ip);