Dept of better ideas: refrain from creating the planner's placeholder_list

until vars are distributed to rels during query_planner() startup.  We don't
really need it before that, and not building it early has some advantages.
First, we don't need to put it through the various preprocessing steps, which
saves some cycles and eliminates the need for a number of routines to support
PlaceHolderInfo nodes at all.  Second, this means one less unused plan for any
sub-SELECT appearing in a placeholder's expression, since we don't build
placeholder_list until after sublink expansion is complete.

Author: tglsfdc

src/backend/optimizer/plan/planmain.c

@@ -14,7 +14,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/optimizer/plan/planmain.c,v 1.111 2008/10/21 20:42:53 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/optimizer/plan/planmain.c,v 1.112 2008/10/22 20:17:51 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -133,7 +133,7 @@ query_planner(PlannerInfo *root, List *tlist,
 	 * for "simple" rels.
 	 *
 	 * NOTE: append_rel_list was set up by subquery_planner, so do not touch
-	 * here; ditto placeholder_list; eq_classes may contain data already, too.
+	 * here; eq_classes may contain data already, too.
 	 */
 	root->simple_rel_array_size = list_length(parse->rtable) + 1;
 	root->simple_rel_array = (RelOptInfo **)
@@ -145,6 +145,7 @@ query_planner(PlannerInfo *root, List *tlist,
 	root->right_join_clauses = NIL;
 	root->full_join_clauses = NIL;
 	root->join_info_list = NIL;
+	root->placeholder_list = NIL;
 	root->initial_rels = NIL;
 
 	/*

src/backend/optimizer/plan/planner.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/optimizer/plan/planner.c,v 1.245 2008/10/21 20:42:53 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/optimizer/plan/planner.c,v 1.246 2008/10/22 20:17:51 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -55,7 +55,7 @@ planner_hook_type planner_hook = NULL;
 #define EXPRKIND_RTFUNC		2
 #define EXPRKIND_VALUES		3
 #define EXPRKIND_LIMIT		4
-#define EXPRKIND_AUXINFO	5
+#define EXPRKIND_APPINFO	5
 
 
 static Node *preprocess_expression(PlannerInfo *root, Node *expr, int kind);
@@ -274,7 +274,6 @@ subquery_planner(PlannerGlobal *glob, Query *parse,
 	root->cte_plan_ids = NIL;
 	root->eq_classes = NIL;
 	root->append_rel_list = NIL;
-	root->placeholder_list = NIL;
 
 	root->hasRecursion = hasRecursion;
 	if (hasRecursion)
@@ -380,10 +379,7 @@ subquery_planner(PlannerGlobal *glob, Query *parse,
 
 	root->append_rel_list = (List *)
 		preprocess_expression(root, (Node *) root->append_rel_list,
-							  EXPRKIND_AUXINFO);
-	root->placeholder_list = (List *)
-		preprocess_expression(root, (Node *) root->placeholder_list,
-							  EXPRKIND_AUXINFO);
+							  EXPRKIND_APPINFO);
 
 	/* Also need to preprocess expressions for function and values RTEs */
 	foreach(l, parse->rtable)
@@ -664,11 +660,10 @@ inheritance_planner(PlannerInfo *root)
 		subroot.returningLists = NIL;
 		subroot.init_plans = NIL;
 		/* We needn't modify the child's append_rel_list */
-		subroot.placeholder_list = (List *)
-			adjust_appendrel_attrs((Node *) root->placeholder_list,
-								   appinfo);
 		/* There shouldn't be any OJ info to translate, as yet */
 		Assert(subroot.join_info_list == NIL);
+		/* and we haven't created PlaceHolderInfos, either */
+		Assert(subroot.placeholder_list == NIL);
 
 		/* Generate plan */
 		subplan = grouping_planner(&subroot, 0.0 /* retrieve all tuples */ );

src/backend/optimizer/prep/prepjointree.c

@@ -16,7 +16,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/optimizer/prep/prepjointree.c,v 1.57 2008/10/21 20:42:53 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/optimizer/prep/prepjointree.c,v 1.58 2008/10/22 20:17:52 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -565,7 +565,6 @@ pull_up_simple_subquery(PlannerInfo *root, Node *jtnode, RangeTblEntry *rte,
 	subroot->cte_plan_ids = NIL;
 	subroot->eq_classes = NIL;
 	subroot->append_rel_list = NIL;
-	subroot->placeholder_list = NIL;
 	subroot->hasRecursion = false;
 	subroot->wt_param_id = -1;
 	subroot->non_recursive_plan = NULL;
@@ -627,20 +626,18 @@ pull_up_simple_subquery(PlannerInfo *root, Node *jtnode, RangeTblEntry *rte,
 	/*
 	 * Adjust level-0 varnos in subquery so that we can append its rangetable
 	 * to upper query's.  We have to fix the subquery's append_rel_list
-	 * and placeholder_list as well.
+	 * as well.
 	 */
 	rtoffset = list_length(parse->rtable);
 	OffsetVarNodes((Node *) subquery, rtoffset, 0);
 	OffsetVarNodes((Node *) subroot->append_rel_list, rtoffset, 0);
-	OffsetVarNodes((Node *) subroot->placeholder_list, rtoffset, 0);
 
 	/*
 	 * Upper-level vars in subquery are now one level closer to their parent
 	 * than before.
 	 */
 	IncrementVarSublevelsUp((Node *) subquery, -1, 1);
 	IncrementVarSublevelsUp((Node *) subroot->append_rel_list, -1, 1);
-	IncrementVarSublevelsUp((Node *) subroot->placeholder_list, -1, 1);
 
 	/*
 	 * The subquery's targetlist items are now in the appropriate form to
@@ -706,48 +703,42 @@ pull_up_simple_subquery(PlannerInfo *root, Node *jtnode, RangeTblEntry *rte,
 	parse->rowMarks = list_concat(parse->rowMarks, subquery->rowMarks);
 
 	/*
-	 * We also have to fix the relid sets of any FlattenedSubLink,
-	 * PlaceHolderVar, and PlaceHolderInfo nodes in the parent query.
-	 * (This could perhaps be done by ResolveNew, but it would clutter that
-	 * routine's API unreasonably.)  Note in particular that any placeholder
-	 * nodes just created by insert_targetlist_placeholders() wiil be adjusted.
+	 * We also have to fix the relid sets of any FlattenedSubLink and
+	 * PlaceHolderVar nodes in the parent query.  (This could perhaps be done
+	 * by ResolveNew, but it would clutter that routine's API unreasonably.)
+	 * Note in particular that any PlaceHolderVar nodes just created by
+	 * insert_targetlist_placeholders() will be adjusted, so having created
+	 * them with the subquery's varno is correct.
 	 *
 	 * Likewise, relids appearing in AppendRelInfo nodes have to be fixed (but
 	 * we took care of their translated_vars lists above).	We already checked
 	 * that this won't require introducing multiple subrelids into the
 	 * single-slot AppendRelInfo structs.
 	 */
-	if (parse->hasSubLinks || root->placeholder_list || root->append_rel_list)
+	if (parse->hasSubLinks || root->glob->lastPHId != 0 ||
+		root->append_rel_list)
 	{
 		Relids		subrelids;
 
 		subrelids = get_relids_in_jointree((Node *) subquery->jointree, false);
-		substitute_multiple_relids((Node *) parse,
-								   varno, subrelids);
-		substitute_multiple_relids((Node *) root->placeholder_list,
-								   varno, subrelids);
-		fix_append_rel_relids(root->append_rel_list,
-							  varno, subrelids);
+		substitute_multiple_relids((Node *) parse, varno, subrelids);
+		fix_append_rel_relids(root->append_rel_list, varno, subrelids);
 	}
 
 	/*
-	 * And now add subquery's AppendRelInfos and PlaceHolderInfos to our lists.
-	 * Note that any placeholders pulled up from the subquery will appear
-	 * after any we just created; this preserves the property that placeholders
-	 * can only refer to other placeholders that appear later in the list
-	 * (needed by fix_placeholder_eval_levels).
+	 * And now add subquery's AppendRelInfos to our list.
 	 */
 	root->append_rel_list = list_concat(root->append_rel_list,
 										subroot->append_rel_list);
-	root->placeholder_list = list_concat(root->placeholder_list,
-										 subroot->placeholder_list);
 
 	/*
 	 * We don't have to do the equivalent bookkeeping for outer-join info,
-	 * because that hasn't been set up yet.
+	 * because that hasn't been set up yet.  placeholder_list likewise.
 	 */
 	Assert(root->join_info_list == NIL);
 	Assert(subroot->join_info_list == NIL);
+	Assert(root->placeholder_list == NIL);
+	Assert(subroot->placeholder_list == NIL);
 
 	/*
 	 * Miscellaneous housekeeping.
@@ -1606,10 +1597,10 @@ reduce_outer_joins_pass2(Node *jtnode,
  * substitute_multiple_relids - adjust node relid sets after pulling up
  * a subquery
  *
- * Find any FlattenedSubLink, PlaceHolderVar, or PlaceHolderInfo nodes in the
- * given tree that reference the pulled-up relid, and change them to reference
- * the replacement relid(s).  We do not need to recurse into subqueries, since
- * no subquery of the current top query could (yet) contain such a reference.
+ * Find any FlattenedSubLink or PlaceHolderVar nodes in the given tree that
+ * reference the pulled-up relid, and change them to reference the replacement
+ * relid(s).  We do not need to recurse into subqueries, since no subquery of
+ * the current top query could (yet) contain such a reference.
  *
  * NOTE: although this has the form of a walker, we cheat and modify the
  * nodes in-place.  This should be OK since the tree was copied by ResolveNew
@@ -1662,26 +1653,11 @@ substitute_multiple_relids_walker(Node *node,
 		}
 		/* fall through to examine children */
 	}
-	if (IsA(node, PlaceHolderInfo))
-	{
-		PlaceHolderInfo *phinfo = (PlaceHolderInfo *) node;
+	/* Shouldn't need to handle planner auxiliary nodes here */
+	Assert(!IsA(node, SpecialJoinInfo));
+	Assert(!IsA(node, AppendRelInfo));
+	Assert(!IsA(node, PlaceHolderInfo));
 
-		if (bms_is_member(context->varno, phinfo->ph_eval_at))
-		{
-			phinfo->ph_eval_at = bms_union(phinfo->ph_eval_at,
-										   context->subrelids);
-			phinfo->ph_eval_at = bms_del_member(phinfo->ph_eval_at,
-												context->varno);
-		}
-		if (bms_is_member(context->varno, phinfo->ph_needed))
-		{
-			phinfo->ph_needed = bms_union(phinfo->ph_needed,
-										  context->subrelids);
-			phinfo->ph_needed = bms_del_member(phinfo->ph_needed,
-											   context->varno);
-		}
-		/* fall through to examine children */
-	}
 	return expression_tree_walker(node, substitute_multiple_relids_walker,
 								  (void *) context);
 }

src/backend/optimizer/prep/prepunion.c

@@ -22,7 +22,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/optimizer/prep/prepunion.c,v 1.159 2008/10/21 20:42:53 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/optimizer/prep/prepunion.c,v 1.160 2008/10/22 20:17:52 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -1599,26 +1599,10 @@ adjust_appendrel_attrs_mutator(Node *node, AppendRelInfo *context)
 										   context->child_relid);
 		return (Node *) phv;
 	}
-	if (IsA(node, PlaceHolderInfo))
-	{
-		/* Copy the PlaceHolderInfo node with correct mutation of subnodes */
-		PlaceHolderInfo *phinfo;
-
-		phinfo = (PlaceHolderInfo *) expression_tree_mutator(node,
-											  adjust_appendrel_attrs_mutator,
-															 (void *) context);
-		/* now fix PlaceHolderInfo's relid sets */
-		phinfo->ph_eval_at = adjust_relid_set(phinfo->ph_eval_at,
-											  context->parent_relid,
-											  context->child_relid);
-		phinfo->ph_needed = adjust_relid_set(phinfo->ph_needed,
-											 context->parent_relid,
-											 context->child_relid);
-		return (Node *) phinfo;
-	}
-	/* Shouldn't need to handle other planner auxiliary nodes here */
+	/* Shouldn't need to handle planner auxiliary nodes here */
 	Assert(!IsA(node, SpecialJoinInfo));
 	Assert(!IsA(node, AppendRelInfo));
+	Assert(!IsA(node, PlaceHolderInfo));
 
 	/*
 	 * We have to process RestrictInfo nodes specially.