Improve Recursive CTE tests (#3274)

Postgres keeps track of recursive CTEs in the queryTree in two ways:

   - queryTree->hasRecursive is set to true, whenever a RECURSIVE CTE
     is used in the SQL. Citus checks for it
   - If the CTE is actually a recursive one (a.k.a., references itself)
     Postgres marks CommonTableExpr->cterecursive as true as well

The tests that are changed in the PR doesn't cover (b), and this becomes
an issue with CTE inlining (#3161). In that case, Citus/Postgres can inline
such CTEs, and the queries works with Citus.

However, this tests intend to check if there is any recursive CTE in the queryTree.
So, we're actually making the CTEs recursive CTEs by referring itself.

We'll add cases where a recursive CTE works by inlining in #3161.

src/test/regress/expected/with_basics.out

@@ -100,7 +100,7 @@ WITH cte AS (
 )
 SELECT (SELECT * FROM cte);
 ERROR:  more than one row returned by a subquery used as an expression
-CONTEXT:  while executing command on localhost:57637
+CONTEXT:  while executing command on localhost:57638
 WITH cte_basic AS (
 	SELECT user_id FROM users_table WHERE user_id = 1
 )
@@ -651,14 +651,14 @@ SELECT * FROM cte UNION ALL SELECT * FROM cte_2;
 WITH RECURSIVE basic_recursive(x) AS (
     VALUES (1)
   UNION ALL
-    SELECT user_id + 1 FROM users_table WHERE user_id < 100
+    SELECT user_id + 1 FROM users_table JOIN basic_recursive ON (user_id = x) WHERE user_id < 100
 )
 SELECT sum(x) FROM basic_recursive;
 ERROR:  recursive CTEs are not supported in distributed queries
 WITH RECURSIVE basic_recursive AS (
     SELECT -1 as user_id, '2017-11-22 20:16:16.614779'::timestamp, -1, -1, -1, -1
   UNION ALL
-    SELECT * FROM users_table WHERE user_id>1
+    SELECT basic_recursive.* FROM users_table JOIN basic_recursive USING (user_id) WHERE user_id>1
 )
 SELECT * FROM basic_recursive ORDER BY user_id LIMIT 1;
 ERROR:  recursive CTEs are not supported in distributed queries
@@ -669,7 +669,7 @@ FROM
 (WITH RECURSIVE basic_recursive AS (
       SELECT -1 as user_id, '2017-11-22 20:16:16.614779'::timestamp, -1, -1, -1, -1
     UNION ALL
-      SELECT * FROM users_table WHERE user_id>1
+      SELECT basic_recursive.* FROM users_table JOIN basic_recursive USING (user_id) WHERE user_id>1
   )
   SELECT * FROM basic_recursive ORDER BY user_id LIMIT 1) cte_rec;
 ERROR:  recursive CTEs are not supported in distributed queries
@@ -683,7 +683,7 @@ WHERE
 (WITH RECURSIVE basic_recursive AS (
       SELECT -1 as user_id
     UNION ALL
-      SELECT user_id FROM users_table WHERE user_id>1
+      SELECT basic_recursive.* FROM users_table JOIN basic_recursive USING (user_id) WHERE user_id>1
   )
   SELECT * FROM basic_recursive ORDER BY user_id LIMIT 1);
 ERROR:  recursive CTEs are not supported in distributed queries
@@ -691,7 +691,7 @@ ERROR:  recursive CTEs are not supported in distributed queries
 WITH RECURSIVE basic_recursive(x) AS(
     VALUES (1)
   UNION ALL
-    SELECT user_id + 1 FROM users_table WHERE user_id < 100
+    SELECT user_id + 1 FROM users_table JOIN basic_recursive ON (user_id = x) WHERE user_id < 100
 ),
 basic AS (
     SELECT count(user_id) FROM users_table
@@ -702,7 +702,7 @@ ERROR:  recursive CTEs are not supported in distributed queries
 WITH RECURSIVE basic_recursive(x) AS(
     VALUES (1)
   UNION ALL
-    SELECT user_id + 1 FROM users_table WHERE user_id < 100
+    SELECT user_id + 1 FROM users_table JOIN basic_recursive ON (user_id = x) WHERE user_id < 100
 ),
 basic AS (
     SELECT count(x) FROM basic_recursive
@@ -712,10 +712,10 @@ ERROR:  recursive CTEs are not supported in distributed queries
 -- recursive CTE in a NESTED manner
 WITH regular_cte AS (
   WITH regular_2 AS (
-    WITH RECURSIVE recursive AS (
+    WITH RECURSIVE recursive(x) AS (
         VALUES (1)
       UNION ALL
-        SELECT user_id + 1 FROM users_table WHERE user_id < 100
+        SELECT user_id + 1 FROM users_table JOIN recursive ON (user_id = x) WHERE user_id < 100
     )
     SELECT * FROM recursive
   )

src/test/regress/sql/with_basics.sql

@@ -401,14 +401,14 @@ SELECT * FROM cte UNION ALL SELECT * FROM cte_2;
 WITH RECURSIVE basic_recursive(x) AS (
     VALUES (1)
   UNION ALL
-    SELECT user_id + 1 FROM users_table WHERE user_id < 100
+    SELECT user_id + 1 FROM users_table JOIN basic_recursive ON (user_id = x) WHERE user_id < 100
 )
 SELECT sum(x) FROM basic_recursive;
 
 WITH RECURSIVE basic_recursive AS (
     SELECT -1 as user_id, '2017-11-22 20:16:16.614779'::timestamp, -1, -1, -1, -1
   UNION ALL
-    SELECT * FROM users_table WHERE user_id>1
+    SELECT basic_recursive.* FROM users_table JOIN basic_recursive USING (user_id) WHERE user_id>1
 )
 SELECT * FROM basic_recursive ORDER BY user_id LIMIT 1;
 
@@ -420,7 +420,7 @@ FROM
 (WITH RECURSIVE basic_recursive AS (
       SELECT -1 as user_id, '2017-11-22 20:16:16.614779'::timestamp, -1, -1, -1, -1
     UNION ALL
-      SELECT * FROM users_table WHERE user_id>1
+      SELECT basic_recursive.* FROM users_table JOIN basic_recursive USING (user_id) WHERE user_id>1
   )
   SELECT * FROM basic_recursive ORDER BY user_id LIMIT 1) cte_rec;
 
@@ -435,7 +435,7 @@ WHERE
 (WITH RECURSIVE basic_recursive AS (
       SELECT -1 as user_id
     UNION ALL
-      SELECT user_id FROM users_table WHERE user_id>1
+      SELECT basic_recursive.* FROM users_table JOIN basic_recursive USING (user_id) WHERE user_id>1
   )
   SELECT * FROM basic_recursive ORDER BY user_id LIMIT 1);
 
@@ -444,7 +444,7 @@ WHERE
 WITH RECURSIVE basic_recursive(x) AS(
     VALUES (1)
   UNION ALL
-    SELECT user_id + 1 FROM users_table WHERE user_id < 100
+    SELECT user_id + 1 FROM users_table JOIN basic_recursive ON (user_id = x) WHERE user_id < 100
 ),
 basic AS (
     SELECT count(user_id) FROM users_table
@@ -456,7 +456,7 @@ SELECT x FROM basic, basic_recursive;
 WITH RECURSIVE basic_recursive(x) AS(
     VALUES (1)
   UNION ALL
-    SELECT user_id + 1 FROM users_table WHERE user_id < 100
+    SELECT user_id + 1 FROM users_table JOIN basic_recursive ON (user_id = x) WHERE user_id < 100
 ),
 basic AS (
     SELECT count(x) FROM basic_recursive
@@ -467,10 +467,10 @@ SELECT * FROM basic;
 -- recursive CTE in a NESTED manner
 WITH regular_cte AS (
   WITH regular_2 AS (
-    WITH RECURSIVE recursive AS (
+    WITH RECURSIVE recursive(x) AS (
         VALUES (1)
       UNION ALL
-        SELECT user_id + 1 FROM users_table WHERE user_id < 100
+        SELECT user_id + 1 FROM users_table JOIN recursive ON (user_id = x) WHERE user_id < 100
     )
     SELECT * FROM recursive
   )