fix neo4j schema query (#6381)

Fix issue #6380 

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Fixes #6380  (issue)

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---------

Co-authored-by: HubertKl <HubertKl>

langchain/graphs/neo4j_graph.py

@@ -21,7 +21,8 @@ rel_query = """
 CALL apoc.meta.data()
 YIELD label, other, elementType, type, property
 WHERE type = "RELATIONSHIP" AND elementType = "node"
-RETURN "(:" + label + ")-[:" + property + "]->(:" + toString(other[0]) + ")" AS output
+UNWIND other AS other_node
+RETURN "(:" + label + ")-[:" + property + "]->(:" + toString(other_node) + ")" AS output
 """
 
 

tests/integration_tests/chains/test_graph_database.py

@@ -4,6 +4,11 @@ import os
 from langchain.chains.graph_qa.cypher import GraphCypherQAChain
 from langchain.chains.loading import load_chain
 from langchain.graphs import Neo4jGraph
+from langchain.graphs.neo4j_graph import (
+    node_properties_query,
+    rel_properties_query,
+    rel_query,
+)
 from langchain.llms.openai import OpenAI
 
 
@@ -171,11 +176,62 @@ def test_cypher_return_direct() -> None:
     assert output == expected_output
 
 
+def test_cypher_return_correct_schema() -> None:
+    """Test that chain returns direct results."""
+    url = os.environ.get("NEO4J_URL")
+    username = os.environ.get("NEO4J_USERNAME")
+    password = os.environ.get("NEO4J_PASSWORD")
+    assert url is not None
+    assert username is not None
+    assert password is not None
+
+    graph = Neo4jGraph(
+        url=url,
+        username=username,
+        password=password,
+    )
+    # Delete all nodes in the graph
+    graph.query("MATCH (n) DETACH DELETE n")
+    # Create two nodes and a relationship
+    graph.query(
+        """
+        CREATE (la:LabelA {property_a: 'a'})
+        CREATE (lb:LabelB)
+        CREATE (lc:LabelC)
+        MERGE (la)-[:REL_TYPE]-> (lb)
+        MERGE (la)-[:REL_TYPE {rel_prop: 'abc'}]-> (lc)
+        """
+    )
+    # Refresh schema information
+    graph.refresh_schema()
+
+    node_properties = graph.query(node_properties_query)
+    relationships_properties = graph.query(rel_properties_query)
+    relationships = graph.query(rel_query)
+
+    expected_node_properties = [
+        {
+            "properties": [{"property": "property_a", "type": "STRING"}],
+            "labels": "LabelA",
+        }
+    ]
+    expected_relationships_properties = [
+        {"type": "REL_TYPE", "properties": [{"property": "rel_prop", "type": "STRING"}]}
+    ]
+    expected_relationships = [
+        "(:LabelA)-[:REL_TYPE]->(:LabelB)",
+        "(:LabelA)-[:REL_TYPE]->(:LabelC)",
+    ]
+
+    assert node_properties == expected_node_properties
+    assert relationships_properties == expected_relationships_properties
+    assert relationships == expected_relationships
+
+
 def test_cypher_save_load() -> None:
     """Test saving and loading."""
 
     FILE_PATH = "cypher.yaml"
-
     url = os.environ.get("NEO4J_URL")
     username = os.environ.get("NEO4J_USERNAME")
     password = os.environ.get("NEO4J_PASSWORD")
@@ -188,7 +244,6 @@ def test_cypher_save_load() -> None:
         username=username,
         password=password,
     )
-
     chain = GraphCypherQAChain.from_llm(
         OpenAI(temperature=0), graph=graph, return_direct=True
     )