3 files changed, 39 insertions, 4 deletions
diff --git a/src/include/nodes/execnodes.h b/src/include/nodes/execnodes.h
index ce41c750afc..ee8c4a2bef7 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 1.186 2008/08/07 03:04:03 tgl Exp $
+ * $PostgreSQL: pgsql/src/include/nodes/execnodes.h,v 1.187 2008/08/22 00:16:04 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -628,6 +628,17 @@ typedef struct SubPlanState
 } SubPlanState;
 
 /* ----------------
+ *		AlternativeSubPlanState node
+ * ----------------
+ */
+typedef struct AlternativeSubPlanState
+{
+	ExprState	xprstate;
+	List	   *subplans;		/* states of alternative subplans */
+	int			active;			/* list index of the one we're using */
+} AlternativeSubPlanState;
+
+/* ----------------
  *		FieldSelectState node
  * ----------------
  */
diff --git a/src/include/nodes/nodes.h b/src/include/nodes/nodes.h
index 5fdd23c5a91..b9e00bfddea 100644
--- a/src/include/nodes/nodes.h
+++ b/src/include/nodes/nodes.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/nodes.h,v 1.208 2008/08/14 18:48:00 tgl Exp $
+ * $PostgreSQL: pgsql/src/include/nodes/nodes.h,v 1.209 2008/08/22 00:16:04 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -118,6 +118,7 @@ typedef enum NodeTag
 	T_BoolExpr,
 	T_SubLink,
 	T_SubPlan,
+	T_AlternativeSubPlan,
 	T_FieldSelect,
 	T_FieldStore,
 	T_RelabelType,
@@ -160,6 +161,7 @@ typedef enum NodeTag
 	T_ScalarArrayOpExprState,
 	T_BoolExprState,
 	T_SubPlanState,
+	T_AlternativeSubPlanState,
 	T_FieldSelectState,
 	T_FieldStoreState,
 	T_CoerceViaIOState,
diff --git a/src/include/nodes/primnodes.h b/src/include/nodes/primnodes.h
index f0c55112cbc..f6da1adbfa0 100644
--- a/src/include/nodes/primnodes.h
+++ b/src/include/nodes/primnodes.h
@@ -10,7 +10,7 @@
  * Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/nodes/primnodes.h,v 1.138 2008/08/02 21:32:00 tgl Exp $
+ * $PostgreSQL: pgsql/src/include/nodes/primnodes.h,v 1.139 2008/08/22 00:16:04 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -445,7 +445,8 @@ typedef struct SubLink
  *
  * If the sub-select becomes an initplan rather than a subplan, the executable
  * expression is part of the outer plan's expression tree (and the SubPlan
- * node itself is not).  In this case testexpr is NULL to avoid duplication.
+ * node itself is not, but rather is found in the outer plan's initPlan
+ * list).  In this case testexpr is NULL to avoid duplication.
  *
  * The planner also derives lists of the values that need to be passed into
  * and out of the subplan.	Input values are represented as a list "args" of
@@ -457,6 +458,10 @@ typedef struct SubLink
  * is an initplan; they are listed in order by sub-select output column
  * position.  (parParam and setParam are integer Lists, not Bitmapsets,
  * because their ordering is significant.)
+ *
+ * Also, the planner computes startup and per-call costs for use of the
+ * SubPlan.  Note that these include the cost of the subquery proper,
+ * evaluation of the testexpr if any, and any hashtable management overhead.
  */
 typedef struct SubPlan
 {
@@ -482,8 +487,25 @@ typedef struct SubPlan
 								 * Params for parent plan */
 	List	   *parParam;		/* indices of input Params from parent plan */
 	List	   *args;			/* exprs to pass as parParam values */
+	/* Estimated execution costs: */
+	Cost		startup_cost;	/* one-time setup cost */
+	Cost		per_call_cost;	/* cost for each subplan evaluation */
 } SubPlan;
 
+/*
+ * AlternativeSubPlan - expression node for a choice among SubPlans
+ *
+ * The subplans are given as a List so that the node definition need not
+ * change if there's ever more than two alternatives.  For the moment,
+ * though, there are always exactly two; and the first one is the fast-start
+ * plan.
+ */
+typedef struct AlternativeSubPlan
+{
+	Expr		xpr;
+	List	   *subplans;		/* SubPlan(s) with equivalent results */
+} AlternativeSubPlan;
+
 /* ----------------
  * FieldSelect
  *