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

1 files changed, 58 insertions, 1 deletions

diff --git a/src/include/nodes/execnodes.h b/src/include/nodes/execnodes.h
index eb187ce4597..02c9c8f0566 100644
--- a/src/include/nodes/execnodes.h
+++ b/src/include/nodes/execnodes.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/nodes/execnodes.h,v 1.188 2008/10/01 19:51:49 tgl Exp $
+ * $PostgreSQL: pgsql/src/include/nodes/execnodes.h,v 1.189 2008/10/04 21:56:55 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -947,6 +947,26 @@ typedef struct AppendState
 } AppendState;
 
 /* ----------------
+ *	 RecursiveUnionState information
+ *
+ *		RecursiveUnionState is used for performing a recursive union.
+ *
+ *		recursing			T when we're done scanning the non-recursive term
+ *		intermediate_empty	T if intermediate_table is currently empty
+ *		working_table		working table (to be scanned by recursive term)
+ *		intermediate_table	current recursive output (next generation of WT)
+ * ----------------
+ */
+typedef struct RecursiveUnionState
+{
+	PlanState	ps;				/* its first field is NodeTag */
+	bool		recursing;
+	bool		intermediate_empty;
+	Tuplestorestate *working_table;
+	Tuplestorestate *intermediate_table;
+} RecursiveUnionState;
+
+/* ----------------
  *	 BitmapAndState information
  * ----------------
  */
@@ -1179,6 +1199,43 @@ typedef struct ValuesScanState
 	int			marked_idx;
 } ValuesScanState;
 
+/* ----------------
+ *	 CteScanState information
+ *
+ *		CteScan nodes are used to scan a CommonTableExpr query.
+ *
+ * Multiple CteScan nodes can read out from the same CTE query.  We use
+ * a tuplestore to hold rows that have been read from the CTE query but
+ * not yet consumed by all readers.
+ * ----------------
+ */
+typedef struct CteScanState
+{
+	ScanState	ss;				/* its first field is NodeTag */
+	int			eflags;			/* capability flags to pass to tuplestore */
+	int			readptr;		/* index of my tuplestore read pointer */
+	PlanState  *cteplanstate;	/* PlanState for the CTE query itself */
+	/* Link to the "leader" CteScanState (possibly this same node) */
+	struct CteScanState *leader;
+	/* The remaining fields are only valid in the "leader" CteScanState */
+	Tuplestorestate *cte_table;	/* rows already read from the CTE query */
+	bool		eof_cte;		/* reached end of CTE query? */
+} CteScanState;
+
+/* ----------------
+ *	 WorkTableScanState information
+ *
+ *		WorkTableScan nodes are used to scan the work table created by
+ *		a RecursiveUnion node.  We locate the RecursiveUnion node
+ *		during executor startup.
+ * ----------------
+ */
+typedef struct WorkTableScanState
+{
+	ScanState	ss;				/* its first field is NodeTag */
+	RecursiveUnionState *rustate;
+} WorkTableScanState;
+
 /* ----------------------------------------------------------------
  *				 Join State Information
  * ----------------------------------------------------------------