fix: ensure Milvus collections are loaded before operations

- Resolves "collection not loaded" MilvusException errors

lightrag/kg/milvus_impl.py

@@ -539,6 +539,23 @@ class MilvusVectorDBStorage(BaseVectorStorage):
             )
             raise
 
+    def _ensure_collection_loaded(self):
+        """Ensure the collection is loaded into memory for search operations"""
+        try:
+            # Check if collection exists first
+            if not self._client.has_collection(self.namespace):
+                logger.error(f"Collection {self.namespace} does not exist")
+                raise ValueError(f"Collection {self.namespace} does not exist")
+            
+            # Load the collection if it's not already loaded
+            # In Milvus, collections need to be loaded before they can be searched
+            self._client.load_collection(self.namespace)
+            logger.debug(f"Collection {self.namespace} loaded successfully")
+            
+        except Exception as e:
+            logger.error(f"Failed to load collection {self.namespace}: {e}")
+            raise
+
     def _create_collection_if_not_exist(self):
         """Create collection if not exists and check existing collection compatibility"""
 
@@ -565,6 +582,8 @@ class MilvusVectorDBStorage(BaseVectorStorage):
                         f"Collection '{self.namespace}' confirmed to exist, validating compatibility..."
                     )
                     self._validate_collection_compatibility()
+                    # Ensure the collection is loaded after validation
+                    self._ensure_collection_loaded()
                     return
                 except Exception as describe_error:
                     logger.warning(
@@ -587,6 +606,9 @@ class MilvusVectorDBStorage(BaseVectorStorage):
             # Then create indexes
             self._create_indexes_after_collection()
 
+            # Load the newly created collection
+            self._ensure_collection_loaded()
+
             logger.info(f"Successfully created Milvus collection: {self.namespace}")
 
         except Exception as e:
@@ -615,6 +637,10 @@ class MilvusVectorDBStorage(BaseVectorStorage):
                     collection_name=self.namespace, schema=schema
                 )
                 self._create_indexes_after_collection()
+                
+                # Load the newly created collection
+                self._ensure_collection_loaded()
+                
                 logger.info(f"Successfully force-created collection {self.namespace}")
 
             except Exception as create_error:
@@ -670,6 +696,9 @@ class MilvusVectorDBStorage(BaseVectorStorage):
         if not data:
             return
 
+        # Ensure collection is loaded before upserting
+        self._ensure_collection_loaded()
+
         import time
 
         current_time = int(time.time())
@@ -700,6 +729,9 @@ class MilvusVectorDBStorage(BaseVectorStorage):
     async def query(
         self, query: str, top_k: int, ids: list[str] | None = None
     ) -> list[dict[str, Any]]:
+        # Ensure collection is loaded before querying
+        self._ensure_collection_loaded()
+        
         embedding = await self.embedding_func(
             [query], _priority=5
         )  # higher priority for query
@@ -764,6 +796,9 @@ class MilvusVectorDBStorage(BaseVectorStorage):
             entity_name: The name of the entity whose relations should be deleted
         """
         try:
+            # Ensure collection is loaded before querying
+            self._ensure_collection_loaded()
+            
             # Search for relations where entity is either source or target
             expr = f'src_id == "{entity_name}" or tgt_id == "{entity_name}"'
 
@@ -802,6 +837,9 @@ class MilvusVectorDBStorage(BaseVectorStorage):
             ids: List of vector IDs to be deleted
         """
         try:
+            # Ensure collection is loaded before deleting
+            self._ensure_collection_loaded()
+            
             # Delete vectors by IDs
             result = self._client.delete(collection_name=self.namespace, pks=ids)
 
@@ -825,6 +863,9 @@ class MilvusVectorDBStorage(BaseVectorStorage):
             The vector data if found, or None if not found
         """
         try:
+            # Ensure collection is loaded before querying
+            self._ensure_collection_loaded()
+            
             # Include all meta_fields (created_at is now always included) plus id
             output_fields = list(self.meta_fields) + ["id"]
 
@@ -856,6 +897,9 @@ class MilvusVectorDBStorage(BaseVectorStorage):
             return []
 
         try:
+            # Ensure collection is loaded before querying
+            self._ensure_collection_loaded()
+            
             # Include all meta_fields (created_at is now always included) plus id
             output_fields = list(self.meta_fields) + ["id"]