Cherry-pick 'ae47eb1' from upstream to fix Nested CTE errors (#3360)

Before this cherry-pick the below query would have errored out

WITH outermost(x) AS (
  SELECT 1
  UNION (WITH innermost as (SELECT 2)
         SELECT * FROM innermost
         UNION SELECT 3)
)
SELECT * FROM outermost;
Signed-off-by: NMelanie Plageman <mplageman@pivotal.io>

src/backend/parser/analyze.c

@@ -1861,6 +1861,7 @@ transformSetOperationStmt(ParseState *pstate, SelectStmt *stmt)
 	SelectStmt *leftmostSelect;
 	int			leftmostRTI;
 	Query	   *leftmostQuery;
+	WithClause *withClause;
 	SetOperationStmt *sostmt;
 	List	   *intoColNames = NIL;
 	List	   *sortClause;
@@ -1910,11 +1911,13 @@ transformSetOperationStmt(ParseState *pstate, SelectStmt *stmt)
 	limitOffset = stmt->limitOffset;
 	limitCount = stmt->limitCount;
 	lockingClause = stmt->lockingClause;
+	withClause = stmt->withClause;
 
 	stmt->sortClause = NIL;
 	stmt->limitOffset = NULL;
 	stmt->limitCount = NULL;
 	stmt->lockingClause = NIL;
+	stmt->withClause = NULL;
 
 	/* We don't support FOR UPDATE/SHARE with set ops at the moment. */
 	if (lockingClause)
@@ -1923,10 +1926,10 @@ transformSetOperationStmt(ParseState *pstate, SelectStmt *stmt)
 				 errmsg("SELECT FOR UPDATE/SHARE is not allowed with UNION/INTERSECT/EXCEPT")));
 
 	/* process the WITH clause */
-	if (stmt->withClause)
+	if (withClause)
 	{
-		qry->hasRecursive = stmt->withClause->recursive;
-		qry->cteList = transformWithClause(pstate, stmt->withClause);
+		qry->hasRecursive = withClause->recursive;
+		qry->cteList = transformWithClause(pstate, withClause);
 	}
 
 	/*
@@ -2289,7 +2292,7 @@ transformSetOperationTree_internal(ParseState *pstate, SelectStmt *stmt,
 	{
 		Assert(stmt->larg != NULL && stmt->rarg != NULL);
 		if (stmt->sortClause || stmt->limitOffset || stmt->limitCount ||
-			stmt->lockingClause)
+			stmt->lockingClause || stmt->withClause)
 			isLeaf = true;
 		else
 			isLeaf = false;

src/backend/parser/parse_cte.c

@@ -677,6 +677,18 @@ checkWellFormedRecursion(CteState *cstate)
 		if (cstate->selfrefcount != 1)			/* shouldn't happen */
 			elog(ERROR, "missing recursive reference");
 
+		/* WITH mustn't contain self-reference, either */
+		if (stmt->withClause)
+		{
+			cstate->curitem = i;
+			cstate->innerwiths = NIL;
+			cstate->selfrefcount = 0;
+			cstate->context = RECURSION_SUBLINK;
+			checkWellFormedRecursionWalker((Node *) stmt->withClause->ctes,
+										   cstate);
+			Assert(cstate->innerwiths == NIL);
+		}
+
 		/*
 		 * Disallow ORDER BY and similar decoration atop the UNION ALL.
 		 * These don't make sense because it's impossible to figure out what

src/test/regress/expected/with.out

@@ -788,3 +788,20 @@ from int4_tbl;
  -2147483647
 (5 rows)
 
+--
+-- test Nested CTE
+--
+WITH outermost(x) AS (
+  SELECT 1
+  UNION (WITH innermost as (SELECT 2)
+         SELECT * FROM innermost
+         UNION SELECT 3)
+)
+SELECT * FROM outermost;
+x
+---
+ 1
+ 2
+ 3
+(3 rows)
+

src/test/regress/sql/with.sql

@@ -457,3 +457,14 @@ from int4_tbl;
 select ( with cte(foo) as ( values(f1) )
           values((select foo from cte)) )
 from int4_tbl;
+
+--
+-- test Nested CTE
+--
+WITH outermost(x) AS (
+  SELECT 1
+  UNION (WITH innermost as (SELECT 2)
+         SELECT * FROM innermost
+         UNION SELECT 3)
+)
+SELECT * FROM outermost;