Neo4jWriter fix relationship query (#155)

* Fix relationship upsert query:

- Prevent full db scan by using node labels
- Prevent Cypher syntax error by escaping the relationship type with backticks

* Add note in changelog

Author: stellasia

CHANGELOG.md

@@ -19,6 +19,8 @@
 ### Fixed
 - Resolved import issue with the Vertex AI Embeddings class.
 - Resolved issue where Neo4jWriter component would raise an error if the start or end node ID was not defined properly in the input.
+- Resolved issue where relationship types was not escaped in the insert Cypher query.
+- Improved query performance in Neo4jWriter.
 
 ### Changed
 - Moved the Embedder class to the neo4j_graphrag.embeddings directory for better organization alongside other custom embedders.

src/neo4j_graphrag/neo4j_queries.py

@@ -53,9 +53,9 @@
 )
 
 UPSERT_RELATIONSHIP_QUERY = (
-    "MATCH (start {{ id: $start_node_id }}) "
-    "MATCH (end {{ id: $end_node_id }}) "
-    "MERGE (start)-[r:{type}]->(end) "
+    "MATCH (start:__Entity__ {{ id: $start_node_id }}) "
+    "MATCH (end:__Entity__ {{ id: $end_node_id }}) "
+    "MERGE (start)-[r:`{type}`]->(end) "
     "WITH r SET r += $properties "
     "WITH r CALL {{ "
     "WITH r WITH r WHERE $embeddings IS NOT NULL "