Get rid of the rather fuzzily defined FlattenedSubLink node type in favor of

making pull_up_sublinks() construct a full-blown JoinExpr tree representation
of IN/EXISTS SubLinks that it is able to convert to semi or anti joins.
This makes pull_up_sublinks() a shade more complex, but the gain in semantic
clarity is worth it.  I still have more to do in this area to address the
previously-discussed problems, but this commit in itself fixes at least one
bug in HEAD, as shown by added regression test case.

src/backend/nodes/copyfuncs.c

@@ -15,7 +15,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/nodes/copyfuncs.c,v 1.424 2009/02/24 10:06:32 petere Exp $
+ *	  $PostgreSQL: pgsql/src/backend/nodes/copyfuncs.c,v 1.425 2009/02/25 03:30:37 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -1624,22 +1624,6 @@ _copyRestrictInfo(RestrictInfo *from)
 	return newnode;
 }
 
-/*
- * _copyFlattenedSubLink
- */
-static FlattenedSubLink *
-_copyFlattenedSubLink(FlattenedSubLink *from)
-{
-	FlattenedSubLink *newnode = makeNode(FlattenedSubLink);
-
-	COPY_SCALAR_FIELD(jointype);
-	COPY_BITMAPSET_FIELD(lefthand);
-	COPY_BITMAPSET_FIELD(righthand);
-	COPY_NODE_FIELD(quals);
-
-	return newnode;
-}
-
 /*
  * _copyPlaceHolderVar
  */
@@ -3710,9 +3694,6 @@ copyObject(void *from)
 		case T_RestrictInfo:
 			retval = _copyRestrictInfo(from);
 			break;
-		case T_FlattenedSubLink:
-			retval = _copyFlattenedSubLink(from);
-			break;
 		case T_PlaceHolderVar:
 			retval = _copyPlaceHolderVar(from);
 			break;

src/backend/nodes/equalfuncs.c

@@ -22,7 +22,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/nodes/equalfuncs.c,v 1.348 2009/02/24 10:06:32 petere Exp $
+ *	  $PostgreSQL: pgsql/src/backend/nodes/equalfuncs.c,v 1.349 2009/02/25 03:30:37 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -766,17 +766,6 @@ _equalRestrictInfo(RestrictInfo *a, RestrictInfo *b)
 	return true;
 }
 
-static bool
-_equalFlattenedSubLink(FlattenedSubLink *a, FlattenedSubLink *b)
-{
-	COMPARE_SCALAR_FIELD(jointype);
-	COMPARE_BITMAPSET_FIELD(lefthand);
-	COMPARE_BITMAPSET_FIELD(righthand);
-	COMPARE_NODE_FIELD(quals);
-
-	return true;
-}
-
 static bool
 _equalPlaceHolderVar(PlaceHolderVar *a, PlaceHolderVar *b)
 {
@@ -2496,9 +2485,6 @@ equal(void *a, void *b)
 		case T_RestrictInfo:
 			retval = _equalRestrictInfo(a, b);
 			break;
-		case T_FlattenedSubLink:
-			retval = _equalFlattenedSubLink(a, b);
-			break;
 		case T_PlaceHolderVar:
 			retval = _equalPlaceHolderVar(a, b);
 			break;

src/backend/nodes/nodeFuncs.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/nodes/nodeFuncs.c,v 1.37 2009/01/01 17:23:43 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/nodes/nodeFuncs.c,v 1.38 2009/02/25 03:30:37 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -1309,14 +1309,6 @@ expression_tree_walker(Node *node,
 				/* groupClauses are deemed uninteresting */
 			}
 			break;
-		case T_FlattenedSubLink:
-			{
-				FlattenedSubLink *fslink = (FlattenedSubLink *) node;
-
-				if (walker(fslink->quals, context))
-					return true;
-			}
-			break;
 		case T_PlaceHolderVar:
 			return walker(((PlaceHolderVar *) node)->phexpr, context);
 		case T_AppendRelInfo:
@@ -1972,17 +1964,6 @@ expression_tree_mutator(Node *node,
 				return (Node *) newnode;
 			}
 			break;
-		case T_FlattenedSubLink:
-			{
-				FlattenedSubLink *fslink = (FlattenedSubLink *) node;
-				FlattenedSubLink *newnode;
-
-				FLATCOPY(newnode, fslink, FlattenedSubLink);
-				/* Assume we need not copy the relids bitmapsets */
-				MUTATE(newnode->quals, fslink->quals, Expr *);
-				return (Node *) newnode;
-			}
-			break;
 		case T_PlaceHolderVar:
 			{
 				PlaceHolderVar *phv = (PlaceHolderVar *) node;

src/backend/nodes/outfuncs.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/nodes/outfuncs.c,v 1.352 2009/02/06 23:43:23 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/nodes/outfuncs.c,v 1.353 2009/02/25 03:30:37 tgl Exp $
  *
  * NOTES
  *	  Every node type that can appear in stored rules' parsetrees *must*
@@ -1630,17 +1630,6 @@ _outInnerIndexscanInfo(StringInfo str, InnerIndexscanInfo *node)
 	WRITE_NODE_FIELD(cheapest_total_innerpath);
 }
 
-static void
-_outFlattenedSubLink(StringInfo str, FlattenedSubLink *node)
-{
-	WRITE_NODE_TYPE("FLATTENEDSUBLINK");
-
-	WRITE_ENUM_FIELD(jointype, JoinType);
-	WRITE_BITMAPSET_FIELD(lefthand);
-	WRITE_BITMAPSET_FIELD(righthand);
-	WRITE_NODE_FIELD(quals);
-}
-
 static void
 _outPlaceHolderVar(StringInfo str, PlaceHolderVar *node)
 {
@@ -2660,9 +2649,6 @@ _outNode(StringInfo str, void *obj)
 			case T_InnerIndexscanInfo:
 				_outInnerIndexscanInfo(str, obj);
 				break;
-			case T_FlattenedSubLink:
-				_outFlattenedSubLink(str, obj);
-				break;
 			case T_PlaceHolderVar:
 				_outPlaceHolderVar(str, obj);
 				break;

src/backend/optimizer/plan/initsplan.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/optimizer/plan/initsplan.c,v 1.147 2009/02/20 00:01:03 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/optimizer/plan/initsplan.c,v 1.148 2009/02/25 03:30:37 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -52,9 +52,6 @@ static void distribute_qual_to_rels(PlannerInfo *root, Node *clause,
 						Relids qualscope,
 						Relids ojscope,
 						Relids outerjoin_nonnullable);
-static void distribute_sublink_quals_to_rels(PlannerInfo *root,
-								 FlattenedSubLink *fslink,
-								 bool below_outer_join);
 static bool check_outerjoin_delay(PlannerInfo *root, Relids *relids_p,
 					  bool is_pushed_down);
 static bool check_redundant_nullability_qual(PlannerInfo *root, Node *clause);
@@ -336,15 +333,9 @@ deconstruct_recurse(PlannerInfo *root, Node *jtnode, bool below_outer_join,
 		{
 			Node   *qual = (Node *) lfirst(l);
 
-			/* FlattenedSubLink wrappers need special processing */
-			if (qual && IsA(qual, FlattenedSubLink))
-				distribute_sublink_quals_to_rels(root,
-												 (FlattenedSubLink *) qual,
-												 below_outer_join);
-			else
-				distribute_qual_to_rels(root, qual,
-										false, below_outer_join, JOIN_INNER,
-										*qualscope, NULL, NULL);
+			distribute_qual_to_rels(root, qual,
+									false, below_outer_join, JOIN_INNER,
+									*qualscope, NULL, NULL);
 		}
 	}
 	else if (IsA(jtnode, JoinExpr))
@@ -399,6 +390,18 @@ deconstruct_recurse(PlannerInfo *root, Node *jtnode, bool below_outer_join,
 				*inner_join_rels = bms_union(left_inners, right_inners);
 				nonnullable_rels = leftids;
 				break;
+			case JOIN_SEMI:
+				leftjoinlist = deconstruct_recurse(root, j->larg,
+												   below_outer_join,
+												   &leftids, &left_inners);
+				rightjoinlist = deconstruct_recurse(root, j->rarg,
+													below_outer_join,
+													&rightids, &right_inners);
+				*qualscope = bms_union(leftids, rightids);
+				*inner_join_rels = bms_union(left_inners, right_inners);
+				/* Semi join adds no restrictions for quals */
+				nonnullable_rels = NULL;
+				break;
 			case JOIN_FULL:
 				leftjoinlist = deconstruct_recurse(root, j->larg,
 												   true,
@@ -425,6 +428,9 @@ deconstruct_recurse(PlannerInfo *root, Node *jtnode, bool below_outer_join,
 		 * semantic scope (ojscope) to pass to distribute_qual_to_rels.  But
 		 * we mustn't add it to join_info_list just yet, because we don't want
 		 * distribute_qual_to_rels to think it is an outer join below us.
+		 *
+		 * Semijoins are a bit of a hybrid: we build a SpecialJoinInfo,
+		 * but we want ojscope = NULL for distribute_qual_to_rels.
 		 */
 		if (j->jointype != JOIN_INNER)
 		{
@@ -433,7 +439,11 @@ deconstruct_recurse(PlannerInfo *root, Node *jtnode, bool below_outer_join,
 										*inner_join_rels,
 										j->jointype,
 										(List *) j->quals);
-			ojscope = bms_union(sjinfo->min_lefthand, sjinfo->min_righthand);
+			if (j->jointype == JOIN_SEMI)
+				ojscope = NULL;
+			else
+				ojscope = bms_union(sjinfo->min_lefthand,
+									sjinfo->min_righthand);
 		}
 		else
 		{
@@ -446,16 +456,10 @@ deconstruct_recurse(PlannerInfo *root, Node *jtnode, bool below_outer_join,
 		{
 			Node   *qual = (Node *) lfirst(l);
 
-			/* FlattenedSubLink wrappers need special processing */
-			if (qual && IsA(qual, FlattenedSubLink))
-				distribute_sublink_quals_to_rels(root,
-												 (FlattenedSubLink *) qual,
-												 below_outer_join);
-			else
-				distribute_qual_to_rels(root, qual,
-										false, below_outer_join, j->jointype,
-										*qualscope,
-										ojscope, nonnullable_rels);
+			distribute_qual_to_rels(root, qual,
+									false, below_outer_join, j->jointype,
+									*qualscope,
+									ojscope, nonnullable_rels);
 		}
 
 		/* Now we can add the SpecialJoinInfo to join_info_list */
@@ -1044,64 +1048,6 @@ distribute_qual_to_rels(PlannerInfo *root, Node *clause,
 	distribute_restrictinfo_to_rels(root, restrictinfo);
 }
 
-/*
- * distribute_sublink_quals_to_rels
- *	  Pull sublink quals out of a FlattenedSubLink node and distribute
- *	  them appropriately; then add a SpecialJoinInfo node to the query's
- *	  join_info_list.  The FlattenedSubLink node itself is no longer
- *	  needed and does not propagate into further processing.
- */
-static void
-distribute_sublink_quals_to_rels(PlannerInfo *root,
-								 FlattenedSubLink *fslink,
-								 bool below_outer_join)
-{
-	List	   *quals = make_ands_implicit(fslink->quals);
-	SpecialJoinInfo *sjinfo;
-	Relids		qualscope;
-	Relids		ojscope;
-	Relids		outerjoin_nonnullable;
-	ListCell   *l;
-
-	/*
-	 * Build a suitable SpecialJoinInfo for the sublink.  Note: using
-	 * righthand as inner_join_rels is the conservative worst case;
-	 * it might be possible to use a smaller set and thereby allow
-	 * the sublink join to commute with others inside its RHS.
-	 */
-	sjinfo = make_outerjoininfo(root,
-								fslink->lefthand, fslink->righthand,
-								fslink->righthand,
-								fslink->jointype,
-								quals);
-
-	/* Treat as inner join if SEMI, outer join if ANTI */
-	qualscope = bms_union(sjinfo->syn_lefthand, sjinfo->syn_righthand);
-	if (fslink->jointype == JOIN_SEMI)
-	{
-		ojscope = outerjoin_nonnullable = NULL;
-	}
-	else
-	{
-		Assert(fslink->jointype == JOIN_ANTI);
-		ojscope = bms_union(sjinfo->min_lefthand, sjinfo->min_righthand);
-		outerjoin_nonnullable = fslink->lefthand;
-	}
-
-	/* Distribute the join quals much as for a regular JOIN node */
-	foreach(l, quals)
-	{
-		Node   *qual = (Node *) lfirst(l);
-
-		distribute_qual_to_rels(root, qual,
-								false, below_outer_join, fslink->jointype,
-								qualscope, ojscope, outerjoin_nonnullable);
-	}
-
-	/* Now we can add the SpecialJoinInfo to join_info_list */
-	root->join_info_list = lappend(root->join_info_list, sjinfo);
-}
-
 /*
  * check_outerjoin_delay
  *		Detect whether a qual referencing the given relids must be delayed

src/backend/optimizer/prep/prepunion.c

@@ -22,7 +22,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/optimizer/prep/prepunion.c,v 1.165 2009/02/06 23:43:23 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/optimizer/prep/prepunion.c,v 1.166 2009/02/25 03:30:37 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -1587,23 +1587,6 @@ adjust_appendrel_attrs_mutator(Node *node, AppendRelInfo *context)
 			j->rtindex = context->child_relid;
 		return (Node *) j;
 	}
-	if (IsA(node, FlattenedSubLink))
-	{
-		/* Copy the FlattenedSubLink node with correct mutation of subnodes */
-		FlattenedSubLink *fslink;
-
-		fslink = (FlattenedSubLink *) expression_tree_mutator(node,
-											  adjust_appendrel_attrs_mutator,
-															 (void *) context);
-		/* now fix FlattenedSubLink's relid sets */
-		fslink->lefthand = adjust_relid_set(fslink->lefthand,
-											context->parent_relid,
-											context->child_relid);
-		fslink->righthand = adjust_relid_set(fslink->righthand,
-											 context->parent_relid,
-											 context->child_relid);
-		return (Node *) fslink;
-	}
 	if (IsA(node, PlaceHolderVar))
 	{
 		/* Copy the PlaceHolderVar node with correct mutation of subnodes */

src/backend/optimizer/util/clauses.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/optimizer/util/clauses.c,v 1.275 2009/01/09 15:46:10 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/optimizer/util/clauses.c,v 1.276 2009/02/25 03:30:37 tgl Exp $
  *
  * HISTORY
  *	  AUTHOR			DATE			MAJOR EVENT
@@ -1300,15 +1300,6 @@ find_nonnullable_rels_walker(Node *node, bool top_level)
 			 expr->booltesttype == IS_NOT_UNKNOWN))
 			result = find_nonnullable_rels_walker((Node *) expr->arg, false);
 	}
-	else if (IsA(node, FlattenedSubLink))
-	{
-		/* JOIN_SEMI sublinks preserve strictness, but JOIN_ANTI ones don't */
-		FlattenedSubLink *expr = (FlattenedSubLink *) node;
-
-		if (expr->jointype == JOIN_SEMI)
-			result = find_nonnullable_rels_walker((Node *) expr->quals,
-												  top_level);
-	}
 	else if (IsA(node, PlaceHolderVar))
 	{
 		PlaceHolderVar *phv = (PlaceHolderVar *) node;
@@ -1511,15 +1502,6 @@ find_nonnullable_vars_walker(Node *node, bool top_level)
 			 expr->booltesttype == IS_NOT_UNKNOWN))
 			result = find_nonnullable_vars_walker((Node *) expr->arg, false);
 	}
-	else if (IsA(node, FlattenedSubLink))
-	{
-		/* JOIN_SEMI sublinks preserve strictness, but JOIN_ANTI ones don't */
-		FlattenedSubLink *expr = (FlattenedSubLink *) node;
-
-		if (expr->jointype == JOIN_SEMI)
-			result = find_nonnullable_vars_walker((Node *) expr->quals,
-												  top_level);
-	}
 	else if (IsA(node, PlaceHolderVar))
 	{
 		PlaceHolderVar *phv = (PlaceHolderVar *) node;
@@ -2943,24 +2925,6 @@ eval_const_expressions_mutator(Node *node,
 		newbtest->booltesttype = btest->booltesttype;
 		return (Node *) newbtest;
 	}
-	if (IsA(node, FlattenedSubLink))
-	{
-		FlattenedSubLink *fslink = (FlattenedSubLink *) node;
-		FlattenedSubLink *newfslink;
-		Expr	   *quals;
-
-		/* Simplify and also canonicalize the arguments */
-		quals = (Expr *) eval_const_expressions_mutator((Node *) fslink->quals,
-														context);
-		quals = canonicalize_qual(quals);
-
-		newfslink = makeNode(FlattenedSubLink);
-		newfslink->jointype = fslink->jointype;
-		newfslink->lefthand = fslink->lefthand;
-		newfslink->righthand = fslink->righthand;
-		newfslink->quals = quals;
-		return (Node *) newfslink;
-	}
 	if (IsA(node, PlaceHolderVar) && context->estimate)
 	{
 		/*

src/backend/optimizer/util/var.c

@@ -14,7 +14,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/optimizer/util/var.c,v 1.83 2009/01/01 17:23:45 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/optimizer/util/var.c,v 1.84 2009/02/25 03:30:37 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -766,24 +766,6 @@ flatten_join_alias_vars_mutator(Node *node,
 		/* Recurse in case join input is itself a join */
 		return flatten_join_alias_vars_mutator(newvar, context);
 	}
-	if (IsA(node, FlattenedSubLink))
-	{
-		/* Copy the FlattenedSubLink node with correct mutation of subnodes */
-		FlattenedSubLink *fslink;
-
-		fslink = (FlattenedSubLink *) expression_tree_mutator(node,
-											 flatten_join_alias_vars_mutator,
-															 (void *) context);
-		/* now fix FlattenedSubLink's relid sets */
-		if (context->sublevels_up == 0)
-		{
-			fslink->lefthand = alias_relid_set(context->root,
-											   fslink->lefthand);
-			fslink->righthand = alias_relid_set(context->root,
-												fslink->righthand);
-		}
-		return (Node *) fslink;
-	}
 	if (IsA(node, PlaceHolderVar))
 	{
 		/* Copy the PlaceHolderVar node with correct mutation of subnodes */

src/backend/rewrite/rewriteManip.c

@@ -7,7 +7,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/rewrite/rewriteManip.c,v 1.120 2009/01/01 17:23:47 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/rewrite/rewriteManip.c,v 1.121 2009/02/25 03:30:37 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -348,23 +348,10 @@ OffsetVarNodes_walker(Node *node, OffsetVarNodes_context *context)
 	{
 		JoinExpr   *j = (JoinExpr *) node;
 
-		if (context->sublevels_up == 0)
+		if (j->rtindex && context->sublevels_up == 0)
 			j->rtindex += context->offset;
 		/* fall through to examine children */
 	}
-	if (IsA(node, FlattenedSubLink))
-	{
-		FlattenedSubLink *fslink = (FlattenedSubLink *) node;
-
-		if (context->sublevels_up == 0)
-		{
-			fslink->lefthand = offset_relid_set(fslink->lefthand,
-												context->offset);
-			fslink->righthand = offset_relid_set(fslink->righthand,
-												 context->offset);
-		}
-		/* fall through to examine children */
-	}
 	if (IsA(node, PlaceHolderVar))
 	{
 		PlaceHolderVar *phv = (PlaceHolderVar *) node;
@@ -530,21 +517,6 @@ ChangeVarNodes_walker(Node *node, ChangeVarNodes_context *context)
 			j->rtindex = context->new_index;
 		/* fall through to examine children */
 	}
-	if (IsA(node, FlattenedSubLink))
-	{
-		FlattenedSubLink *fslink = (FlattenedSubLink *) node;
-
-		if (context->sublevels_up == 0)
-		{
-			fslink->lefthand = adjust_relid_set(fslink->lefthand,
-												context->rt_index,
-												context->new_index);
-			fslink->righthand = adjust_relid_set(fslink->righthand,
-												 context->rt_index,
-												 context->new_index);
-		}
-		/* fall through to examine children */
-	}
 	if (IsA(node, PlaceHolderVar))
 	{
 		PlaceHolderVar *phv = (PlaceHolderVar *) node;
@@ -838,7 +810,6 @@ rangeTableEntry_used_walker(Node *node,
 		/* fall through to examine children */
 	}
 	/* Shouldn't need to handle planner auxiliary nodes here */
-	Assert(!IsA(node, FlattenedSubLink));
 	Assert(!IsA(node, PlaceHolderVar));
 	Assert(!IsA(node, SpecialJoinInfo));
 	Assert(!IsA(node, AppendRelInfo));

src/include/nodes/nodes.h

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2009, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/nodes/nodes.h,v 1.220 2009/02/02 19:31:40 alvherre Exp $
+ * $PostgreSQL: pgsql/src/include/nodes/nodes.h,v 1.221 2009/02/25 03:30:37 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -216,7 +216,6 @@ typedef enum NodeTag
 	T_PathKey,
 	T_RestrictInfo,
 	T_InnerIndexscanInfo,
-	T_FlattenedSubLink,
 	T_PlaceHolderVar,
 	T_SpecialJoinInfo,
 	T_AppendRelInfo,

src/include/nodes/primnodes.h

@@ -10,7 +10,7 @@
  * Portions Copyright (c) 1996-2009, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/nodes/primnodes.h,v 1.145 2009/01/01 17:24:00 momjian Exp $
+ * $PostgreSQL: pgsql/src/include/nodes/primnodes.h,v 1.146 2009/02/25 03:30:37 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -1137,7 +1137,9 @@ typedef struct RangeTblRef
  *
  * During parse analysis, an RTE is created for the Join, and its index
  * is filled into rtindex.	This RTE is present mainly so that Vars can
- * be created that refer to the outputs of the join.
+ * be created that refer to the outputs of the join.  The planner sometimes
+ * generates JoinExprs internally; these can have rtindex = 0 if there are
+ * no join alias variables referencing such joins.
  *----------
  */
 typedef struct JoinExpr
@@ -1150,7 +1152,7 @@ typedef struct JoinExpr
 	List	   *using;			/* USING clause, if any (list of String) */
 	Node	   *quals;			/* qualifiers on join, if any */
 	Alias	   *alias;			/* user-written alias clause, if any */
-	int			rtindex;		/* RT index assigned for join */
+	int			rtindex;		/* RT index assigned for join, or 0 */
 } JoinExpr;
 
 /*----------

src/include/nodes/relation.h

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2009, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/nodes/relation.h,v 1.168 2009/02/06 23:43:24 tgl Exp $
+ * $PostgreSQL: pgsql/src/include/nodes/relation.h,v 1.169 2009/02/25 03:30:37 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -1075,30 +1075,6 @@ typedef struct InnerIndexscanInfo
 	Path	   *cheapest_total_innerpath;		/* cheapest total cost */
 } InnerIndexscanInfo;
 
-/*
- * "Flattened SubLinks"
- *
- * When we pull an IN or EXISTS SubLink up into the parent query, the
- * join conditions extracted from the IN/EXISTS clause need to be specially
- * treated in distribute_qual_to_rels processing.  We handle this by
- * wrapping such expressions in a FlattenedSubLink node that identifies
- * the join they come from.  The FlattenedSubLink node is discarded after
- * distribute_qual_to_rels, having served its purpose.
- *
- * Although the planner treats this as an expression node type, it is not
- * recognized by the parser or executor, so we declare it here rather than
- * in primnodes.h.
- */
-
-typedef struct FlattenedSubLink
-{
-	Expr		xpr;
-	JoinType	jointype;		/* must be JOIN_SEMI or JOIN_ANTI */
-	Relids		lefthand;		/* base relids treated as syntactic LHS */
-	Relids		righthand;		/* base relids syntactically within RHS */
-	Expr	   *quals;			/* join quals (in explicit-AND format) */
-} FlattenedSubLink;
-
 /*
  * Placeholder node for an expression to be evaluated below the top level
  * of a plan tree.  This is used during planning to represent the contained
@@ -1171,8 +1147,11 @@ typedef struct PlaceHolderVar
  * For purposes of join selectivity estimation, we create transient
  * SpecialJoinInfo structures for regular inner joins; so it is possible
  * to have jointype == JOIN_INNER in such a structure, even though this is
- * not allowed within join_info_list.  Note that lhs_strict, delay_upper_joins,
- * and join_quals are not set meaningfully for such structs.
+ * not allowed within join_info_list.  We also create transient
+ * SpecialJoinInfos with jointype == JOIN_INNER for outer joins, since for
+ * cost estimation purposes it is sometimes useful to know the join size under
+ * plain innerjoin semantics.  Note that lhs_strict, delay_upper_joins, and
+ * join_quals are not set meaningfully within such structs.
  */
 
 typedef struct SpecialJoinInfo

src/include/optimizer/subselect.h

@@ -5,7 +5,7 @@
  * Portions Copyright (c) 1996-2009, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/optimizer/subselect.h,v 1.35 2009/01/01 17:24:00 momjian Exp $
+ * $PostgreSQL: pgsql/src/include/optimizer/subselect.h,v 1.36 2009/02/25 03:30:38 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -16,13 +16,13 @@
 #include "nodes/relation.h"
 
 extern void SS_process_ctes(PlannerInfo *root);
-extern bool convert_ANY_sublink_to_join(PlannerInfo *root, SubLink *sublink,
-										Relids available_rels,
-										Node **new_qual, List **fromlist);
-extern bool convert_EXISTS_sublink_to_join(PlannerInfo *root, SubLink *sublink,
-										   bool under_not,
-										   Relids available_rels,
-										   Node **new_qual, List **fromlist);
+extern JoinExpr *convert_ANY_sublink_to_join(PlannerInfo *root,
+											 SubLink *sublink,
+											 Relids available_rels);
+extern JoinExpr *convert_EXISTS_sublink_to_join(PlannerInfo *root,
+												SubLink *sublink,
+												bool under_not,
+												Relids available_rels);
 extern Node *SS_replace_correlation_vars(PlannerInfo *root, Node *expr);
 extern Node *SS_process_sublinks(PlannerInfo *root, Node *expr, bool isQual);
 extern void SS_finalize_plan(PlannerInfo *root, Plan *plan,

src/test/regress/expected/join.out

@@ -2333,3 +2333,22 @@ where a.unique1 = 42 and
 ---------+-----+----------+---------+---------
 (0 rows)
 
+--
+-- test proper positioning of one-time quals in EXISTS (8.4devel bug)
+--
+prepare foo(bool) as
+  select count(*) from tenk1 a left join tenk1 b
+    on (a.unique2 = b.unique1 and exists
+        (select 1 from tenk1 c where c.thousand = b.unique2 and $1));
+execute foo(true);
+ count 
+-------
+ 10000
+(1 row)
+
+execute foo(false);
+ count 
+-------
+ 10000
+(1 row)
+

src/test/regress/expected/join_1.out

@@ -2333,3 +2333,22 @@ where a.unique1 = 42 and
 ---------+-----+----------+---------+---------
 (0 rows)
 
+--
+-- test proper positioning of one-time quals in EXISTS (8.4devel bug)
+--
+prepare foo(bool) as
+  select count(*) from tenk1 a left join tenk1 b
+    on (a.unique2 = b.unique1 and exists
+        (select 1 from tenk1 c where c.thousand = b.unique2 and $1));
+execute foo(true);
+ count 
+-------
+ 10000
+(1 row)
+
+execute foo(false);
+ count 
+-------
+ 10000
+(1 row)
+

src/test/regress/sql/join.sql

@@ -495,3 +495,13 @@ select a.unique2, a.ten, b.tenthous, b.unique2, b.hundred
 from tenk1 a left join tenk1 b on a.unique2 = b.tenthous
 where a.unique1 = 42 and
       ((b.unique2 is null and a.ten = 2) or b.hundred = 3);
+
+--
+-- test proper positioning of one-time quals in EXISTS (8.4devel bug)
+--
+prepare foo(bool) as
+  select count(*) from tenk1 a left join tenk1 b
+    on (a.unique2 = b.unique1 and exists
+        (select 1 from tenk1 c where c.thousand = b.unique2 and $1));
+execute foo(true);
+execute foo(false);