Fix from_existing_graph method & normalize the cosine distance (#238)

fixes:
- #237
- #236

Author: galshubeli

libs/community/langchain_community/vectorstores/falkordb_vector.py

@@ -137,6 +137,7 @@ def _get_search_index_query(
                 "CALL db.idx.vector.queryNodes($entity_label, "
                 "$entity_property, $k, vecf32($embedding)) "
                 "YIELD node, score "
+                "WITH node, (2 - score) / 2 AS score "
             )
         elif search_type == SearchType.HYBRID:
             return (
@@ -1245,8 +1246,8 @@ def from_existing_graph(
                 f"MATCH (n:`{node_label}`) "
                 f"WHERE n.`{embedding_node_property}` IS null "
                 "AND any(k IN $props WHERE n[k] IS NOT null) "
-                "RETURN id(n) AS id, "
-                "coalesce(n.text, '') AS text "
+                "RETURN id(n) AS id, reduce(str='',"
+                "k IN $props | str + '\\n' + k + ':' + coalesce(n[k], '')) AS text "
                 "LIMIT 1000"
             )
             data = store._query(fetch_query, params={"props": text_node_properties})