community[patch]: Update Memgraph support (#16360)

- **Description:** I removed two queries to the database and left just
one whose results were formatted afterward into other type of schema
(avoided two calls to DB)
  - **Issue:** /
  - **Dependencies:** /
  - **Twitter handle:** @supe_katarina

libs/community/langchain_community/graphs/memgraph_graph.py

@@ -1,12 +1,6 @@
 from langchain_community.graphs.neo4j_graph import Neo4jGraph
 
 SCHEMA_QUERY = """
-CALL llm_util.schema("prompt_ready")
-YIELD *
-RETURN *
-"""
-
-RAW_SCHEMA_QUERY = """
 CALL llm_util.schema("raw")
 YIELD *
 RETURN *
@@ -39,10 +33,39 @@ class MemgraphGraph(Neo4jGraph):
         Refreshes the Memgraph graph schema information.
         """
 
-        db_schema = self.query(SCHEMA_QUERY)[0].get("schema")
-        assert db_schema is not None
-        self.schema = db_schema
-
-        db_structured_schema = self.query(RAW_SCHEMA_QUERY)[0].get("schema")
+        db_structured_schema = self.query(SCHEMA_QUERY)[0].get("schema")
         assert db_structured_schema is not None
         self.structured_schema = db_structured_schema
+
+        # Format node properties
+        formatted_node_props = []
+
+        for node_name, properties in db_structured_schema["node_props"].items():
+            formatted_node_props.append(
+                f"Node name: '{node_name}', Node properties: {properties}"
+            )
+
+        # Format relationship properties
+        formatted_rel_props = []
+        for rel_name, properties in db_structured_schema["rel_props"].items():
+            formatted_rel_props.append(
+                f"Relationship name: '{rel_name}', "
+                f"Relationship properties: {properties}"
+            )
+
+        # Format relationships
+        formatted_rels = [
+            f"(:{rel['start']})-[:{rel['type']}]->(:{rel['end']})"
+            for rel in db_structured_schema["relationships"]
+        ]
+
+        self.schema = "\n".join(
+            [
+                "Node properties are the following:",
+                *formatted_node_props,
+                "Relationship properties are the following:",
+                *formatted_rel_props,
+                "The relationships are the following:",
+                *formatted_rels,
+            ]
+        )

libs/community/tests/integration_tests/graphs/test_memgraph.py

@@ -0,0 +1,62 @@
+import os
+
+from langchain_community.graphs import MemgraphGraph
+
+
+def test_cypher_return_correct_schema() -> None:
+    """Test that chain returns direct results."""
+    url = os.environ.get("MEMGRAPH_URI", "bolt://localhost:7687")
+    username = os.environ.get("MEMGRAPH_USERNAME", "")
+    password = os.environ.get("MEMGRAPH_PASSWORD", "")
+    assert url is not None
+    assert username is not None
+    assert password is not None
+
+    graph = MemgraphGraph(
+        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()
+    relationships = graph.query(
+        "CALL llm_util.schema('raw') YIELD schema "
+        "WITH schema.relationships AS relationships "
+        "UNWIND relationships AS relationship "
+        "RETURN relationship['start'] AS start, "
+        "relationship['type'] AS type, "
+        "relationship['end'] AS end "
+        "ORDER BY start, type, end;"
+    )
+
+    node_props = graph.query(
+        "CALL llm_util.schema('raw') YIELD schema "
+        "WITH schema.node_props AS nodes "
+        "WITH nodes['LabelA'] AS properties "
+        "UNWIND properties AS property "
+        "RETURN property['property'] AS prop, "
+        "property['type'] AS type "
+        "ORDER BY prop ASC;"
+    )
+
+    expected_relationships = [
+        {"start": "LabelA", "type": "REL_TYPE", "end": "LabelB"},
+        {"start": "LabelA", "type": "REL_TYPE", "end": "LabelC"},
+    ]
+
+    expected_node_props = [{"prop": "property_a", "type": "str"}]
+
+    assert relationships == expected_relationships
+    assert node_props == expected_node_props