Fix MyPy type checking errors in ClickZetta vector implementation

- Add proper type annotations for Connection from clickzetta module
- Implement _ensure_connection() method to handle None connection checks
- Fix all database cursor access patterns to use proper null checking
- Add type annotation for result queue in _execute_write method
- Resolve factory method configuration issues with None value handling

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

api/core/rag/datasource/vdb/clickzetta/clickzetta_vector.py

@@ -3,11 +3,14 @@ import logging
 import queue
 import threading
 import uuid
-from typing import Any, Optional
+from typing import Any, Optional, TYPE_CHECKING
 
 import clickzetta  # type: ignore
 from pydantic import BaseModel, model_validator
 
+if TYPE_CHECKING:
+    from clickzetta import Connection
+
 from configs import dify_config
 from core.rag.datasource.vdb.field import Field
 from core.rag.datasource.vdb.vector_base import BaseVector
@@ -79,7 +82,7 @@ class ClickzettaVector(BaseVector):
         super().__init__(collection_name)
         self._config = config
         self._table_name = collection_name.replace("-", "_").lower()  # Ensure valid table name
-        self._connection = None
+        self._connection: Optional["Connection"] = None
         self._init_connection()
         self._init_write_queue()
 
@@ -96,6 +99,7 @@ class ClickzettaVector(BaseVector):
         )
 
         # Set session parameters for better string handling
+        if self._connection is not None:
             with self._connection.cursor() as cursor:
                 # Use quote mode for string literal escaping to handle quotes better
                 cursor.execute("SET cz.sql.string.literal.escape.mode = 'quote'")
@@ -117,6 +121,7 @@ class ClickzettaVector(BaseVector):
         while not cls._shutdown:
             try:
                 # Get task from queue with timeout
+                if cls._write_queue is not None:
                     task = cls._write_queue.get(timeout=1)
                     if task is None:  # Shutdown signal
                         break
@@ -131,6 +136,8 @@ class ClickzettaVector(BaseVector):
                         result_queue.put((False, e))
                     finally:
                         cls._write_queue.task_done()
+                else:
+                    break
             except queue.Empty:
                 continue
             except Exception as e:
@@ -141,7 +148,7 @@ class ClickzettaVector(BaseVector):
         if ClickzettaVector._write_queue is None:
             raise RuntimeError("Write queue not initialized")
 
-        result_queue = queue.Queue()
+        result_queue: queue.Queue[tuple[bool, Any]] = queue.Queue()
         ClickzettaVector._write_queue.put((func, args, kwargs, result_queue))
 
         # Wait for result
@@ -154,10 +161,17 @@ class ClickzettaVector(BaseVector):
         """Return the vector database type."""
         return "clickzetta"
 
+    def _ensure_connection(self) -> "Connection":
+        """Ensure connection is available and return it."""
+        if self._connection is None:
+            raise RuntimeError("Database connection not initialized")
+        return self._connection
+
     def _table_exists(self) -> bool:
         """Check if the table exists."""
         try:
-            with self._connection.cursor() as cursor:
+            connection = self._ensure_connection()
+            with connection.cursor() as cursor:
                 cursor.execute(f"DESC {self._config.schema_name}.{self._table_name}")
                 return True
         except Exception as e:
@@ -197,7 +211,8 @@ class ClickzettaVector(BaseVector):
         ) COMMENT 'Dify RAG knowledge base vector storage table for document embeddings and content'
         """
 
-        with self._connection.cursor() as cursor:
+        connection = self._ensure_connection()
+        with connection.cursor() as cursor:
             cursor.execute(create_table_sql)
             logger.info(f"Created table {self._config.schema_name}.{self._table_name}")
 
@@ -369,7 +384,8 @@ class ClickzettaVector(BaseVector):
             f"VALUES (?, ?, CAST(? AS JSON), CAST(? AS VECTOR({vector_dimension})))"
         )
 
-        with self._connection.cursor() as cursor:
+        connection = self._ensure_connection()
+        with connection.cursor() as cursor:
             try:
                 cursor.executemany(insert_sql, data_rows)
                 logger.info(
@@ -385,7 +401,8 @@ class ClickzettaVector(BaseVector):
     def text_exists(self, id: str) -> bool:
         """Check if a document exists by ID."""
         safe_id = self._safe_doc_id(id)
-        with self._connection.cursor() as cursor:
+        connection = self._ensure_connection()
+        with connection.cursor() as cursor:
             cursor.execute(
                 f"SELECT COUNT(*) FROM {self._config.schema_name}.{self._table_name} WHERE id = ?",
                 [safe_id]
@@ -413,7 +430,8 @@ class ClickzettaVector(BaseVector):
         id_list = ",".join(f"'{id}'" for id in safe_ids)
         sql = f"DELETE FROM {self._config.schema_name}.{self._table_name} WHERE id IN ({id_list})"
 
-        with self._connection.cursor() as cursor:
+        connection = self._ensure_connection()
+        with connection.cursor() as cursor:
             cursor.execute(sql)
 
     def delete_by_metadata_field(self, key: str, value: str) -> None:
@@ -428,7 +446,8 @@ class ClickzettaVector(BaseVector):
 
     def _delete_by_metadata_field_impl(self, key: str, value: str) -> None:
         """Implementation of delete by metadata field (executed in write worker thread)."""
-        with self._connection.cursor() as cursor:
+        connection = self._ensure_connection()
+        with connection.cursor() as cursor:
             # Using JSON path to filter with parameterized query
             # Note: JSON path requires literal key name, cannot be parameterized
             # Use json_extract_string function for ClickZetta compatibility
@@ -488,7 +507,8 @@ class ClickzettaVector(BaseVector):
         """
 
         documents = []
-        with self._connection.cursor() as cursor:
+        connection = self._ensure_connection()
+        with connection.cursor() as cursor:
             cursor.execute(search_sql)
             results = cursor.fetchall()
 
@@ -572,7 +592,8 @@ class ClickzettaVector(BaseVector):
         """
 
         documents = []
-        with self._connection.cursor() as cursor:
+        connection = self._ensure_connection()
+        with connection.cursor() as cursor:
             try:
                 cursor.execute(search_sql)
                 results = cursor.fetchall()
@@ -649,7 +670,8 @@ class ClickzettaVector(BaseVector):
         """
 
         documents = []
-        with self._connection.cursor() as cursor:
+        connection = self._ensure_connection()
+        with connection.cursor() as cursor:
             cursor.execute(search_sql)
             results = cursor.fetchall()
 
@@ -689,7 +711,8 @@ class ClickzettaVector(BaseVector):
 
     def delete(self) -> None:
         """Delete the entire collection."""
-        with self._connection.cursor() as cursor:
+        connection = self._ensure_connection()
+        with connection.cursor() as cursor:
             cursor.execute(f"DROP TABLE IF EXISTS {self._config.schema_name}.{self._table_name}")
 
 
@@ -718,13 +741,13 @@ class ClickzettaVectorFactory(AbstractVectorFactory):
         """Initialize a Clickzetta vector instance."""
         # Get configuration from environment variables or dataset config
         config = ClickzettaConfig(
-            username=dify_config.CLICKZETTA_USERNAME,
-            password=dify_config.CLICKZETTA_PASSWORD,
-            instance=dify_config.CLICKZETTA_INSTANCE,
-            service=dify_config.CLICKZETTA_SERVICE,
-            workspace=dify_config.CLICKZETTA_WORKSPACE,
-            vcluster=dify_config.CLICKZETTA_VCLUSTER,
-            schema_name=dify_config.CLICKZETTA_SCHEMA,
+            username=dify_config.CLICKZETTA_USERNAME or "",
+            password=dify_config.CLICKZETTA_PASSWORD or "",
+            instance=dify_config.CLICKZETTA_INSTANCE or "",
+            service=dify_config.CLICKZETTA_SERVICE or "api.clickzetta.com",
+            workspace=dify_config.CLICKZETTA_WORKSPACE or "quick_start",
+            vcluster=dify_config.CLICKZETTA_VCLUSTER or "default_ap",
+            schema_name=dify_config.CLICKZETTA_SCHEMA or "dify",
             batch_size=dify_config.CLICKZETTA_BATCH_SIZE or 100,
             enable_inverted_index=dify_config.CLICKZETTA_ENABLE_INVERTED_INDEX or True,
             analyzer_type=dify_config.CLICKZETTA_ANALYZER_TYPE or "chinese",