fix: add missing self._lock to query_relationship, timeline, stats in KnowledgeGraph

mempalace/knowledge_graph.py

@@ -260,7 +260,6 @@ class KnowledgeGraph:
     def query_relationship(self, predicate: str, as_of: str = None):
         """Get all triples with a given relationship type."""
         pred = predicate.lower().replace(" ", "_")
-        conn = self._conn()
         query = """
             SELECT t.*, s.name as sub_name, o.name as obj_name
             FROM triples t
@@ -274,6 +273,8 @@ class KnowledgeGraph:
             params.extend([as_of, as_of])
 
         results = []
+        with self._lock:
+            conn = self._conn()
             for row in conn.execute(query, params).fetchall():
                 results.append(
                     {
@@ -289,6 +290,7 @@ class KnowledgeGraph:
 
     def timeline(self, entity_name: str = None):
         """Get all facts in chronological order, optionally filtered by entity."""
+        with self._lock:
             conn = self._conn()
             if entity_name:
                 eid = self._entity_id(entity_name)
@@ -329,6 +331,7 @@ class KnowledgeGraph:
     # ── Stats ─────────────────────────────────────────────────────────────
 
     def stats(self):
+        with self._lock:
             conn = self._conn()
             entities = conn.execute("SELECT COUNT(*) as cnt FROM entities").fetchone()["cnt"]
             triples = conn.execute("SELECT COUNT(*) as cnt FROM triples").fetchone()["cnt"]