Reimplement the linked list data structure used throughout the backend.

In the past, we used a 'Lispy' linked list implementation: a "list" was
merely a pointer to the head node of the list. The problem with that
design is that it makes lappend() and length() linear time. This patch
fixes that problem (and others) by maintaining a count of the list
length and a pointer to the tail node along with each head node pointer.
A "list" is now a pointer to a structure containing some meta-data
about the list; the head and tail pointers in that structure refer
to ListCell structures that maintain the actual linked list of nodes.

The function names of the list API have also been changed to, I hope,
be more logically consistent. By default, the old function names are
still available; they will be disabled-by-default once the rest of
the tree has been updated to use the new API names.

1 files changed, 32 insertions, 31 deletions

diff --git a/src/backend/optimizer/plan/planner.c b/src/backend/optimizer/plan/planner.c
index e094620d620..7b5d44c732b 100644
--- a/src/backend/optimizer/plan/planner.c
+++ b/src/backend/optimizer/plan/planner.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/optimizer/plan/planner.c,v 1.169 2004/05/11 02:21:37 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/optimizer/plan/planner.c,v 1.170 2004/05/26 04:41:24 neilc Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -174,6 +174,7 @@ subquery_planner(Query *parse, double tuple_fraction)
 	Plan	   *plan;
 	List	   *newHaving;
 	List	   *lst;
+	ListCell   *l;
 
 	/* Set up for a new level of subquery */
 	PlannerQueryLevel++;
@@ -206,9 +207,9 @@ subquery_planner(Query *parse, double tuple_fraction)
 	 */
 	parse->hasJoinRTEs = false;
 	hasOuterJoins = false;
-	foreach(lst, parse->rtable)
+	foreach(l, parse->rtable)
 	{
-		RangeTblEntry *rte = (RangeTblEntry *) lfirst(lst);
+		RangeTblEntry *rte = (RangeTblEntry *) lfirst(l);
 
 		if (rte->rtekind == RTE_JOIN)
 		{
@@ -244,9 +245,9 @@ subquery_planner(Query *parse, double tuple_fraction)
 							  EXPRKIND_ININFO);
 
 	/* Also need to preprocess expressions for function RTEs */
-	foreach(lst, parse->rtable)
+	foreach(l, parse->rtable)
 	{
-		RangeTblEntry *rte = (RangeTblEntry *) lfirst(lst);
+		RangeTblEntry *rte = (RangeTblEntry *) lfirst(l);
 
 		if (rte->rtekind == RTE_FUNCTION)
 			rte->funcexpr = preprocess_expression(parse, rte->funcexpr,
@@ -271,9 +272,9 @@ subquery_planner(Query *parse, double tuple_fraction)
 	 * declared as Node *.
 	 */
 	newHaving = NIL;
-	foreach(lst, (List *) parse->havingQual)
+	foreach(l, (List *) parse->havingQual)
 	{
-		Node	   *havingclause = (Node *) lfirst(lst);
+		Node	   *havingclause = (Node *) lfirst(l);
 
 		if (contain_agg_clause(havingclause))
 			newHaving = lappend(newHaving, havingclause);
@@ -337,9 +338,9 @@ subquery_planner(Query *parse, double tuple_fraction)
 		 */
 		plan->initPlan = PlannerInitPlan;
 
-		foreach(lst, plan->initPlan)
+		foreach(l, plan->initPlan)
 		{
-			SubPlan    *initplan = (SubPlan *) lfirst(lst);
+			SubPlan    *initplan = (SubPlan *) lfirst(l);
 
 			plan->extParam = bms_add_members(plan->extParam,
 											 initplan->plan->extParam);
@@ -445,7 +446,7 @@ preprocess_qual_conditions(Query *parse, Node *jtnode)
 	else if (IsA(jtnode, FromExpr))
 	{
 		FromExpr   *f = (FromExpr *) jtnode;
-		List	   *l;
+		ListCell   *l;
 
 		foreach(l, f->fromlist)
 			preprocess_qual_conditions(parse, lfirst(l));
@@ -495,7 +496,7 @@ inheritance_planner(Query *parse, List *inheritlist)
 	int			mainrtlength = length(parse->rtable);
 	List	   *subplans = NIL;
 	List	   *tlist = NIL;
-	List	   *l;
+	ListCell   *l;
 
 	foreach(l, inheritlist)
 	{
@@ -524,10 +525,9 @@ inheritance_planner(Query *parse, List *inheritlist)
 		subrtlength = length(subquery->rtable);
 		if (subrtlength > mainrtlength)
 		{
-			List	   *subrt = subquery->rtable;
+			List	   *subrt;
 
-			while (mainrtlength-- > 0)	/* wish we had nthcdr() */
-				subrt = lnext(subrt);
+			subrt = list_copy_tail(subquery->rtable, mainrtlength);
 			parse->rtable = nconc(parse->rtable, subrt);
 			mainrtlength = subrtlength;
 		}
@@ -650,7 +650,7 @@ grouping_planner(Query *parse, double tuple_fraction)
 		 */
 		if (parse->rowMarks)
 		{
-			List	   *l;
+			ListCell   *l;
 
 			/*
 			 * We've got trouble if the FOR UPDATE appears inside
@@ -1328,7 +1328,7 @@ grouping_planner(Query *parse, double tuple_fraction)
 static bool
 hash_safe_grouping(Query *parse)
 {
-	List	   *gl;
+	ListCell   *gl;
 
 	foreach(gl, parse->groupClause)
 	{
@@ -1435,17 +1435,17 @@ make_subplanTargetList(Query *parse,
 	{
 		int			keyno = 0;
 		AttrNumber *grpColIdx;
-		List	   *gl;
+		ListCell   *gl;
 
 		grpColIdx = (AttrNumber *) palloc(sizeof(AttrNumber) * numCols);
 		*groupColIdx = grpColIdx;
 
 		foreach(gl, parse->groupClause)
 		{
-			GroupClause *grpcl = (GroupClause *) lfirst(gl);
-			Node	   *groupexpr = get_sortgroupclause_expr(grpcl, tlist);
-			TargetEntry *te = NULL;
-			List	   *sl;
+			GroupClause		*grpcl = (GroupClause *) lfirst(gl);
+			Node			*groupexpr = get_sortgroupclause_expr(grpcl, tlist);
+			TargetEntry		*te = NULL;
+			ListCell		*sl;
 
 			/* Find or make a matching sub_tlist entry */
 			foreach(sl, sub_tlist)
@@ -1489,7 +1489,7 @@ locate_grouping_columns(Query *parse,
 						AttrNumber *groupColIdx)
 {
 	int			keyno = 0;
-	List	   *gl;
+	ListCell   *gl;
 
 	/*
 	 * No work unless grouping.
@@ -1503,10 +1503,10 @@ locate_grouping_columns(Query *parse,
 
 	foreach(gl, parse->groupClause)
 	{
-		GroupClause *grpcl = (GroupClause *) lfirst(gl);
-		Node	   *groupexpr = get_sortgroupclause_expr(grpcl, tlist);
-		TargetEntry *te = NULL;
-		List	   *sl;
+		GroupClause		*grpcl = (GroupClause *) lfirst(gl);
+		Node			*groupexpr = get_sortgroupclause_expr(grpcl, tlist);
+		TargetEntry		*te = NULL;
+		ListCell		*sl;
 
 		foreach(sl, sub_tlist)
 		{
@@ -1534,7 +1534,8 @@ locate_grouping_columns(Query *parse,
 static List *
 postprocess_setop_tlist(List *new_tlist, List *orig_tlist)
 {
-	List	   *l;
+	ListCell   *l;
+	ListCell   *orig_tlist_item = list_head(orig_tlist);
 
 	foreach(l, new_tlist)
 	{
@@ -1545,16 +1546,16 @@ postprocess_setop_tlist(List *new_tlist, List *orig_tlist)
 		if (new_tle->resdom->resjunk)
 			continue;
 
-		Assert(orig_tlist != NIL);
-		orig_tle = (TargetEntry *) lfirst(orig_tlist);
-		orig_tlist = lnext(orig_tlist);
+		Assert(orig_tlist_item != NULL);
+		orig_tle = (TargetEntry *) lfirst(orig_tlist_item);
+		orig_tlist_item = lnext(orig_tlist_item);
 		if (orig_tle->resdom->resjunk)	/* should not happen */
 			elog(ERROR, "resjunk output columns are not implemented");
 		Assert(new_tle->resdom->resno == orig_tle->resdom->resno);
 		Assert(new_tle->resdom->restype == orig_tle->resdom->restype);
 		new_tle->resdom->ressortgroupref = orig_tle->resdom->ressortgroupref;
 	}
-	if (orig_tlist != NIL)
+	if (orig_tlist_item != NULL)
 		elog(ERROR, "resjunk output columns are not implemented");
 	return new_tlist;
 }