Implement SQL-standard WITH clauses, including WITH RECURSIVE.

There are some unimplemented aspects: recursive queries must use UNION ALL
(should allow UNION too), and we don't have SEARCH or CYCLE clauses.
These might or might not get done for 8.4, but even without them it's a
pretty useful feature.

There are also a couple of small loose ends and definitional quibbles,
which I'll send a memo about to pgsql-hackers shortly.  But let's land
the patch now so we can get on with other development.

Yoshiyuki Asaba, with lots of help from Tatsuo Ishii and Tom Lane

3 files changed, 34 insertions, 2 deletions

diff --git a/src/include/parser/parse_cte.h b/src/include/parser/parse_cte.h
new file mode 100644
index 00000000000..142e833f3e1
--- /dev/null
+++ b/src/include/parser/parse_cte.h
@@ -0,0 +1,21 @@
+/*-------------------------------------------------------------------------
+ *
+ * parse_cte.h
+ *	  handle CTEs (common table expressions) in parser
+ *
+ *
+ * Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * $PostgreSQL: pgsql/src/include/parser/parse_cte.h,v 1.1 2008/10/04 21:56:55 tgl Exp $
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef PARSE_CTE_H
+#define PARSE_CTE_H
+
+#include "parser/parse_node.h"
+
+extern List *transformWithClause(ParseState *pstate, WithClause *withClause);
+
+#endif   /* PARSE_CTE_H */
diff --git a/src/include/parser/parse_node.h b/src/include/parser/parse_node.h
index 460655d3b14..05817cf51a3 100644
--- a/src/include/parser/parse_node.h
+++ b/src/include/parser/parse_node.h
@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/parser/parse_node.h,v 1.56 2008/09/01 20:42:45 tgl Exp $
+ * $PostgreSQL: pgsql/src/include/parser/parse_node.h,v 1.57 2008/10/04 21:56:55 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -50,6 +50,10 @@
  * implicit RTEs into p_relnamespace but not p_varnamespace, so that they
  * do not affect the set of columns available for unqualified references.
  *
+ * p_ctenamespace: list of CommonTableExprs (WITH items) that are visible
+ * at the moment.  This is different from p_relnamespace because you have
+ * to make an RTE before you can access a CTE.
+ *
  * p_paramtypes: an array of p_numparams type OIDs for $n parameter symbols
  * (zeroth entry in array corresponds to $1).  If p_variableparams is true, the
  * set of param types is not predetermined; in that case, a zero array entry
@@ -68,6 +72,7 @@ typedef struct ParseState
 								 * node's fromlist) */
 	List	   *p_relnamespace; /* current namespace for relations */
 	List	   *p_varnamespace; /* current namespace for columns */
+	List	   *p_ctenamespace; /* current namespace for common table exprs */
 	Oid		   *p_paramtypes;	/* OIDs of types for $n parameter symbols */
 	int			p_numparams;	/* allocated size of p_paramtypes[] */
 	int			p_next_resno;	/* next targetlist resno to assign */
diff --git a/src/include/parser/parse_relation.h b/src/include/parser/parse_relation.h
index 1c4e1b6b8ed..9c81d4b50b5 100644
--- a/src/include/parser/parse_relation.h
+++ b/src/include/parser/parse_relation.h
@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/parser/parse_relation.h,v 1.58 2008/09/01 20:42:45 tgl Exp $
+ * $PostgreSQL: pgsql/src/include/parser/parse_relation.h,v 1.59 2008/10/04 21:56:55 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -31,6 +31,7 @@ extern int RTERangeTablePosn(ParseState *pstate,
 extern RangeTblEntry *GetRTEByRangeTablePosn(ParseState *pstate,
 					   int varno,
 					   int sublevels_up);
+extern CommonTableExpr *GetCTEForRTE(ParseState *pstate, RangeTblEntry *rte);
 extern Node *scanRTEForColumn(ParseState *pstate, RangeTblEntry *rte,
 				 char *colname, int location);
 extern Node *colNameToVar(ParseState *pstate, char *colname, bool localonly,
@@ -72,6 +73,11 @@ extern RangeTblEntry *addRangeTableEntryForJoin(ParseState *pstate,
 						  List *aliasvars,
 						  Alias *alias,
 						  bool inFromCl);
+extern RangeTblEntry *addRangeTableEntryForCTE(ParseState *pstate,
+						 CommonTableExpr *cte,
+						 Index levelsup,
+						 Alias *alias,
+						 bool inFromCl);
 extern void addRTEtoQuery(ParseState *pstate, RangeTblEntry *rte,
 			  bool addToJoinList,
 			  bool addToRelNameSpace, bool addToVarNameSpace);