Clean up plantree representation of SubPlan-s --- SubLink does not appear

in the planned representation of a subplan at all any more, only SubPlan.
This means subselect.c doesn't scribble on its input anymore, which seems
like a good thing; and there are no longer three different possible
interpretations of a SubLink.  Simplify node naming and improve comments
in primnodes.h.  No change to stored rules, though.

7 files changed, 72 insertions, 66 deletions

diff --git a/src/include/executor/executor.h b/src/include/executor/executor.h
index bdcb3a6afa5..9b7af6d36fb 100644
--- a/src/include/executor/executor.h
+++ b/src/include/executor/executor.h
@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $Id: executor.h,v 1.82 2002/12/13 19:45:56 tgl Exp $
+ * $Id: executor.h,v 1.83 2002/12/14 00:17:59 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -92,8 +92,7 @@ extern Datum ExecEvalExpr(ExprState *expression, ExprContext *econtext,
 extern Datum ExecEvalExprSwitchContext(ExprState *expression, ExprContext *econtext,
 						  bool *isNull, ExprDoneCond *isDone);
 extern ExprState *ExecInitExpr(Expr *node, PlanState *parent);
-extern SubPlanExprState *ExecInitExprInitPlan(SubPlanExpr *node,
-											  PlanState *parent);
+extern SubPlanState *ExecInitExprInitPlan(SubPlan *node, PlanState *parent);
 extern bool ExecQual(List *qual, ExprContext *econtext, bool resultForNull);
 extern int	ExecTargetListLength(List *targetlist);
 extern int	ExecCleanTargetListLength(List *targetlist);
diff --git a/src/include/executor/nodeSubplan.h b/src/include/executor/nodeSubplan.h
index 97f4b66bcd6..8a3e74ebd1c 100644
--- a/src/include/executor/nodeSubplan.h
+++ b/src/include/executor/nodeSubplan.h
@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $Id: nodeSubplan.h,v 1.14 2002/12/13 19:45:56 tgl Exp $
+ * $Id: nodeSubplan.h,v 1.15 2002/12/14 00:17:59 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -16,13 +16,13 @@
 
 #include "nodes/execnodes.h"
 
-extern void ExecInitSubPlan(SubPlanExprState *sstate, EState *estate);
-extern Datum ExecSubPlan(SubPlanExprState *node,
+extern void ExecInitSubPlan(SubPlanState *node, EState *estate);
+extern Datum ExecSubPlan(SubPlanState *node,
 						 ExprContext *econtext,
 						 bool *isNull);
-extern void ExecEndSubPlan(SubPlanExprState *node);
-extern void ExecReScanSetParamPlan(SubPlanExprState *node, PlanState *parent);
+extern void ExecEndSubPlan(SubPlanState *node);
+extern void ExecReScanSetParamPlan(SubPlanState *node, PlanState *parent);
 
-extern void ExecSetParamPlan(SubPlanExprState *node, ExprContext *econtext);
+extern void ExecSetParamPlan(SubPlanState *node, ExprContext *econtext);
 
 #endif   /* NODESUBPLAN_H */
diff --git a/src/include/nodes/execnodes.h b/src/include/nodes/execnodes.h
index 905bfae6d87..f8e1f7cc4c9 100644
--- a/src/include/nodes/execnodes.h
+++ b/src/include/nodes/execnodes.h
@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $Id: execnodes.h,v 1.84 2002/12/13 19:45:57 tgl Exp $
+ * $Id: execnodes.h,v 1.85 2002/12/14 00:17:59 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -451,21 +451,18 @@ typedef struct BoolExprState
 } BoolExprState;
 
 /* ----------------
- *		SubPlanExprState node
- *
- * Note: there is no separate ExprState node for the SubLink.  All it would
- * need is the oper field, which we can just as easily put here.
+ *		SubPlanState node
  * ----------------
  */
-typedef struct SubPlanExprState
+typedef struct SubPlanState
 {
 	ExprState	xprstate;
 	struct PlanState *planstate; /* subselect plan's state tree */
 	bool		needShutdown;	/* TRUE = need to shutdown subplan */
 	HeapTuple	curTuple;		/* copy of most recent tuple from subplan */
-	List	   *args;			/* states of argument expression(s) */
 	List	   *oper;			/* states for executable combining exprs */
-} SubPlanExprState;
+	List	   *args;			/* states of argument expression(s) */
+} SubPlanState;
 
 /* ----------------
  *		CaseExprState node
@@ -538,9 +535,9 @@ typedef struct PlanState
 	List	   *qual;			/* implicitly-ANDed qual conditions */
 	struct PlanState *lefttree;	/* input plan tree(s) */
 	struct PlanState *righttree;
-	List	   *initPlan;		/* Init SubPlanExprState nodes (un-correlated
+	List	   *initPlan;		/* Init SubPlanState nodes (un-correlated
 								 * expr subselects) */
-	List	   *subPlan;		/* SubPlanExprState nodes in my expressions */
+	List	   *subPlan;		/* SubPlanState nodes in my expressions */
 
 	/*
 	 * State for management of parameter-change-driven rescanning
diff --git a/src/include/nodes/nodes.h b/src/include/nodes/nodes.h
index cc550131852..5f628168738 100644
--- a/src/include/nodes/nodes.h
+++ b/src/include/nodes/nodes.h
@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $Id: nodes.h,v 1.132 2002/12/13 19:46:00 tgl Exp $
+ * $Id: nodes.h,v 1.133 2002/12/14 00:17:59 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -107,7 +107,7 @@ typedef enum NodeTag
 	T_DistinctExpr,
 	T_BoolExpr,
 	T_SubLink,
-	T_SubPlanExpr,
+	T_SubPlan,
 	T_FieldSelect,
 	T_RelabelType,
 	T_CaseExpr,
@@ -133,7 +133,7 @@ typedef enum NodeTag
 	T_ArrayRefExprState,
 	T_FuncExprState,
 	T_BoolExprState,
-	T_SubPlanExprState,
+	T_SubPlanState,
 	T_CaseExprState,
 	T_CaseWhenState,
 	T_ConstraintTestState,
diff --git a/src/include/nodes/params.h b/src/include/nodes/params.h
index c8bc2857ed8..8d7aa3ab32b 100644
--- a/src/include/nodes/params.h
+++ b/src/include/nodes/params.h
@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $Id: params.h,v 1.20 2002/12/13 19:46:00 tgl Exp $
+ * $Id: params.h,v 1.21 2002/12/14 00:17:59 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -88,7 +88,7 @@ typedef ParamListInfoData *ParamListInfo;
  *	  array of ParamExecData records, which is referenced through
  *	  es_param_exec_vals or ecxt_param_exec_vals.
  *
- *	  If execPlan is not NULL, it points to a SubPlanExprState node that needs
+ *	  If execPlan is not NULL, it points to a SubPlanState node that needs
  *	  to be executed to produce the value.  (This is done so that we can have
  *	  lazy evaluation of InitPlans: they aren't executed until/unless a
  *	  result value is needed.)  Otherwise the value is assumed to be valid
@@ -98,7 +98,7 @@ typedef ParamListInfoData *ParamListInfo;
 
 typedef struct ParamExecData
 {
-	void	   *execPlan;		/* should be "SubPlanExprState *" */
+	void	   *execPlan;		/* should be "SubPlanState *" */
 	Datum		value;
 	bool		isnull;
 } ParamExecData;
diff --git a/src/include/nodes/primnodes.h b/src/include/nodes/primnodes.h
index 01a6dbf8d64..285a0008fdc 100644
--- a/src/include/nodes/primnodes.h
+++ b/src/include/nodes/primnodes.h
@@ -10,7 +10,7 @@
  * Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $Id: primnodes.h,v 1.74 2002/12/13 19:46:00 tgl Exp $
+ * $Id: primnodes.h,v 1.75 2002/12/14 00:17:59 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -378,32 +378,21 @@ typedef struct BoolExpr
  * using AND and OR semantics respectively.
  *
  * SubLink is classed as an Expr node, but it is not actually executable;
- * it must be replaced in the expression tree by a SubPlanExpr node during
+ * it must be replaced in the expression tree by a SubPlan node during
  * planning.
  *
- * NOTE: lefthand and oper have varying meanings depending on where you look
- * in the parse/plan pipeline:
- * 1. gram.y delivers a list of the (untransformed) lefthand expressions in
- *	  lefthand, and sets oper to a single A_Expr (not a list!) containing
- *	  the string name of the operator, but no arguments.
- * 2. The parser's expression transformation transforms lefthand normally,
- *	  and replaces oper with a list of OpExpr nodes, one per lefthand
- *	  expression.  These nodes represent the parser's resolution of exactly
- *	  which operator to apply to each pair of lefthand and targetlist
- *	  expressions.	However, we have not constructed complete Expr trees for
- *	  these operations yet: the args fields of the OpExpr nodes are NIL.
- *	  This is the representation seen in saved rules and in the rewriter.
- * 3. Finally, the planner converts the oper list to a list of normal OpExpr
- *	  nodes representing the application of the operator(s) to the lefthand
- *	  expressions and values from the inner targetlist.  The inner
- *	  targetlist items are represented by placeholder Param nodes.
- *	  The lefthand field is set to NIL, since its expressions are now in
- *	  the Expr list.  This representation is passed to the executor.
- *
- * Planner routines that might see either representation 2 or 3 can tell
- * the difference by checking whether lefthand is NIL or not.  Also,
- * representation 2 appears in a "bare" SubLink, while representation 3 is
- * found in SubLinks that are children of SubPlanExpr nodes.
+ * NOTE: in the raw output of gram.y, lefthand contains a list of (raw)
+ * expressions, and oper contains a single A_Expr (not a list!) containing
+ * the string name of the operator, but no arguments.  Also, subselect is
+ * a raw parsetree.  During parse analysis, the parser transforms the
+ * lefthand expression list using normal expression transformation rules.
+ * It replaces oper with a list of OpExpr nodes, one per lefthand expression.
+ * These nodes represent the parser's resolution of exactly which operator
+ * to apply to each pair of lefthand and targetlist expressions.  However,
+ * we have not constructed complete Expr trees for these operations yet:
+ * the args fields of the OpExpr nodes are NIL.  And subselect is transformed
+ * to a Query.  This is the representation seen in saved rules and in the
+ * rewriter.
  *
  * In EXISTS and EXPR SubLinks, both lefthand and oper are unused and are
  * always NIL.	useor is not significant either for these sublink types.
@@ -423,37 +412,58 @@ typedef struct SubLink
 								 * "OR" not "AND" */
 	List	   *lefthand;		/* list of outer-query expressions on the
 								 * left */
-	List	   *oper;			/* list of OpExpr nodes for combining
-								 * operators, or final list of executable
-								 * expressions */
+	List	   *oper;			/* list of arg-less OpExpr nodes for
+								 * combining operators */
 	Node	   *subselect;		/* subselect as Query* or parsetree */
 } SubLink;
 
 /*
- * SubPlanExpr - executable expression node for a subplan (sub-SELECT)
- *
- * The planner replaces SubLink nodes in expression trees with SubPlanExpr
- * nodes after it has finished planning the subquery.  See notes above.
- */
-typedef struct SubPlanExpr
+ * SubPlan - executable expression node for a subplan (sub-SELECT)
+ *
+ * The planner replaces SubLink nodes in expression trees with SubPlan
+ * nodes after it has finished planning the subquery.  SubPlan contains
+ * a sub-plantree and rtable instead of a sub-Query.  Its "oper" field
+ * corresponds to the original SubLink's oper list, but has been expanded
+ * into valid executable expressions representing the application of the
+ * combining operator(s) to the lefthand expressions and values from the
+ * inner targetlist.  The original lefthand expressions now appear as
+ * left-hand arguments of the OpExpr nodes, while the inner targetlist items
+ * are represented by PARAM_EXEC Param nodes.  (Note: if the sub-select
+ * becomes an InitPlan rather than a SubPlan, the rebuilt oper list is
+ * part of the outer plan tree and so is not stored in the oper field.)
+ *
+ * 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
+ * expressions to be evaluated in the outer-query context (currently these
+ * args are always just Vars, but in principle they could be any expression).
+ * The values are assigned to the global PARAM_EXEC params indexed by parParam
+ * (the parParam and args lists must have the same length).  setParam is a
+ * list of the PARAM_EXEC params that are computed by the sub-select, if it
+ * is an initPlan.
+ */
+typedef struct SubPlan
 {
 	Expr		xpr;
-	Oid			typeOid;		/* PG_TYPE OID of the expression result */
+	/* Fields copied from original SubLink: */
+	SubLinkType subLinkType;	/* EXISTS, ALL, ANY, MULTIEXPR, EXPR */
+	bool		useor;			/* TRUE to combine column results with
+								 * "OR" not "AND" */
+	List	   *oper;			/* list of executable expressions for
+								 * combining operators (with arguments) */
+	/* The subselect, transformed to a Plan: */
 	struct Plan *plan;			/* subselect plan itself */
 	int			plan_id;		/* dummy thing because of we haven't equal
 								 * funcs for plan nodes... actually, we
 								 * could put *plan itself somewhere else
 								 * (TopPlan node ?)... */
 	List	   *rtable;			/* range table for subselect */
+	/* Information for passing params into and out of the subselect: */
 	/* setParam and parParam are lists of integers (param IDs) */
 	List	   *setParam;		/* non-correlated EXPR & EXISTS subqueries
 								 * have to set some Params for paren Plan */
 	List	   *parParam;		/* indices of input Params from parent plan */
 	List	   *args;			/* exprs to pass as parParam values */
-	SubLink    *sublink;		/* SubLink node from parser; holds info
-								 * about what to do with subselect's
-								 * results */
-} SubPlanExpr;
+} SubPlan;
 
 /* ----------------
  * FieldSelect
diff --git a/src/include/optimizer/clauses.h b/src/include/optimizer/clauses.h
index 8da7a8688ef..f280e420d9b 100644
--- a/src/include/optimizer/clauses.h
+++ b/src/include/optimizer/clauses.h
@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $Id: clauses.h,v 1.57 2002/12/12 15:49:41 tgl Exp $
+ * $Id: clauses.h,v 1.58 2002/12/14 00:17:59 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -20,7 +20,7 @@
 
 #define is_opclause(clause)		((clause) != NULL && IsA(clause, OpExpr))
 #define is_funcclause(clause)	((clause) != NULL && IsA(clause, FuncExpr))
-#define is_subplan(clause)		((clause) != NULL && IsA(clause, SubPlanExpr))
+#define is_subplan(clause)		((clause) != NULL && IsA(clause, SubPlan))
 
 
 extern Expr *make_opclause(Oid opno, Oid opresulttype, bool opretset,