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.

Author: tglsfdc

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