implementation of tantivy datastore + updated RPC calls to deal with tantivy + docs

src/server.rs

@@ -23,6 +23,9 @@ pub struct Server {
     pub queued_cmd: Option<Vec<(Cmd, Protocol)>>,
     pub current_permissions: Option<crate::rpc::Permissions>,
 
+    // In-memory registry of Tantivy search indexes for this server
+    pub search_indexes: Arc<std::sync::RwLock<HashMap<String, Arc<crate::tantivy_search::TantivySearch>>>>,
+
     // BLPOP waiter registry: per (db_index, key) FIFO of waiters
     pub list_waiters: Arc<Mutex<HashMap<u64, HashMap<String, Vec<Waiter>>>>>,
     pub waiter_seq: Arc<AtomicU64>,
@@ -49,12 +52,25 @@ impl Server {
             selected_db: 0,
             queued_cmd: None,
             current_permissions: None,
-
+    
+            search_indexes: Arc::new(std::sync::RwLock::new(HashMap::new())),
             list_waiters: Arc::new(Mutex::new(HashMap::new())),
             waiter_seq: Arc::new(AtomicU64::new(1)),
         }
     }
 
+    // Path where search indexes are stored, namespaced per selected DB:
+    // <base_dir>/search_indexes/<db_id>
+    pub fn search_index_path(&self) -> std::path::PathBuf {
+        let base = std::path::PathBuf::from(&self.option.dir)
+            .join("search_indexes")
+            .join(self.selected_db.to_string());
+        if !base.exists() {
+            let _ = std::fs::create_dir_all(&base);
+        }
+        base
+    }
+
     pub fn current_storage(&self) -> Result<Arc<dyn StorageBackend>, DBError> {
         let mut cache = self.db_cache.write().unwrap();