much larger improvement to two_hop query performance

queries/queries.sql

@@ -88,23 +88,19 @@ PREPARE two_hop_old (INTEGER) AS
   WHERE vertex <> $1;
 
 PREPARE two_hop_new (INTEGER) AS
-  WITH hop1 AS (
-    SELECT destination vertex
-    FROM edge
+  WITH double_edge AS NOT MATERIALIZED (
+    SELECT source, destination FROM edge
+    UNION ALL
+    SELECT destination, source FROM edge
+  ), hop1 AS NOT MATERIALIZED (
+    SELECT destination AS vertex
+    FROM double_edge
     WHERE source = $1
-    union all
-    select source
-    from edge
-    where destination = $1
-  ), hop2 AS (
-    SELECT source, destination
-    FROM edge
-    JOIN hop1 ON source = vertex OR destination = vertex
   )
-  SELECT DISTINCT vertex
-  FROM (
-    SELECT source AS vertex FROM hop2
+  SELECT vertex
+  FROM hop1
   UNION ALL
-    SELECT destination FROM hop2
-  )
-  WHERE vertex <> $1;
+  SELECT DISTINCT destination
+  FROM double_edge
+  JOIN hop1 ON vertex=source
+  WHERE destination <> $1;