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, 40 insertions, 35 deletions

diff --git a/src/backend/optimizer/plan/subselect.c b/src/backend/optimizer/plan/subselect.c
index af33da1184e..9245da803e2 100644
--- a/src/backend/optimizer/plan/subselect.c
+++ b/src/backend/optimizer/plan/subselect.c
@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/optimizer/plan/subselect.c,v 1.89 2004/05/11 13:15:15 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/optimizer/plan/subselect.c,v 1.90 2004/05/26 04:41:24 neilc Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -101,7 +101,7 @@ static Param *
 replace_outer_var(Var *var)
 {
 	Param	   *retval;
-	List	   *ppl;
+	ListCell   *ppl;
 	PlannerParamItem *pitem;
 	Index		abslevel;
 	int			i;
@@ -250,7 +250,6 @@ make_subplan(SubLink *slink, List *lefthand, bool isTopQual)
 	Plan	   *plan;
 	Bitmapset  *tmpset;
 	int			paramid;
-	List	   *lst;
 	Node	   *result;
 
 	/*
@@ -348,7 +347,7 @@ make_subplan(SubLink *slink, List *lefthand, bool isTopQual)
 	}
 	else if (node->parParam == NIL && slink->subLinkType == EXPR_SUBLINK)
 	{
-		TargetEntry *te = lfirst(plan->targetlist);
+		TargetEntry *te = linitial(plan->targetlist);
 		Param	   *prm;
 
 		Assert(!te->resdom->resjunk);
@@ -359,7 +358,7 @@ make_subplan(SubLink *slink, List *lefthand, bool isTopQual)
 	}
 	else if (node->parParam == NIL && slink->subLinkType == ARRAY_SUBLINK)
 	{
-		TargetEntry *te = lfirst(plan->targetlist);
+		TargetEntry *te = linitial(plan->targetlist);
 		Oid			arraytype;
 		Param	   *prm;
 
@@ -395,11 +394,12 @@ make_subplan(SubLink *slink, List *lefthand, bool isTopQual)
 			result = (Node *) (node->useOr ? make_orclause(exprs) :
 							   make_andclause(exprs));
 		else
-			result = (Node *) lfirst(exprs);
+			result = (Node *) linitial(exprs);
 	}
 	else
 	{
 		List	   *args;
+		ListCell   *l;
 
 		/*
 		 * We can't convert subplans of ALL_SUBLINK or ANY_SUBLINK types
@@ -471,9 +471,9 @@ make_subplan(SubLink *slink, List *lefthand, bool isTopQual)
 		 * Make node->args from parParam.
 		 */
 		args = NIL;
-		foreach(lst, node->parParam)
+		foreach(l, node->parParam)
 		{
-			PlannerParamItem *pitem = nth(lfirsti(lst), PlannerParamList);
+			PlannerParamItem *pitem = nth(lfirsti(l), PlannerParamList);
 
 			/*
 			 * The Var or Aggref has already been adjusted to have the
@@ -509,15 +509,17 @@ convert_sublink_opers(List *lefthand, List *operOids,
 					  List **righthandIds)
 {
 	List	   *result = NIL;
-	List	   *lst;
+	ListCell   *l, *lefthand_item, *tlist_item;
 
 	*righthandIds = NIL;
+	lefthand_item = list_head(lefthand);
+	tlist_item = list_head(targetlist);
 
-	foreach(lst, operOids)
+	foreach(l, operOids)
 	{
-		Oid			opid = lfirsto(lst);
-		Node	   *leftop = lfirst(lefthand);
-		TargetEntry *te = lfirst(targetlist);
+		Oid			opid = lfirsto(l);
+		Node	   *leftop = (Node *) lfirst(lefthand_item);
+		TargetEntry *te = (TargetEntry *) lfirst(tlist_item);
 		Node	   *rightop;
 		Operator	tup;
 
@@ -574,8 +576,8 @@ convert_sublink_opers(List *lefthand, List *operOids,
 
 		ReleaseSysCache(tup);
 
-		lefthand = lnext(lefthand);
-		targetlist = lnext(targetlist);
+		lefthand_item = lnext(lefthand_item);
+		tlist_item = lnext(tlist_item);
 	}
 
 	return result;
@@ -591,7 +593,7 @@ static bool
 subplan_is_hashable(SubLink *slink, SubPlan *node)
 {
 	double		subquery_size;
-	List	   *opids;
+	ListCell   *l;
 
 	/*
 	 * The sublink type must be "= ANY" --- that is, an IN operator. (We
@@ -602,7 +604,7 @@ subplan_is_hashable(SubLink *slink, SubPlan *node)
 	if (slink->subLinkType != ANY_SUBLINK)
 		return false;
 	if (length(slink->operName) != 1 ||
-		strcmp(strVal(lfirst(slink->operName)), "=") != 0)
+		strcmp(strVal(linitial(slink->operName)), "=") != 0)
 		return false;
 
 	/*
@@ -636,9 +638,9 @@ subplan_is_hashable(SubLink *slink, SubPlan *node)
 	 * different sets of operators with the hash table, but there is no
 	 * obvious usefulness to that at present.)
 	 */
-	foreach(opids, slink->operOids)
+	foreach(l, slink->operOids)
 	{
-		Oid			opid = lfirsto(opids);
+		Oid			opid = lfirsto(l);
 		HeapTuple	tup;
 		Form_pg_operator optup;
 
@@ -690,7 +692,7 @@ convert_IN_to_join(Query *parse, SubLink *sublink)
 	if (sublink->subLinkType != ANY_SUBLINK)
 		return NULL;
 	if (length(sublink->operName) != 1 ||
-		strcmp(strVal(lfirst(sublink->operName)), "=") != 0)
+		strcmp(strVal(linitial(sublink->operName)), "=") != 0)
 		return NULL;
 
 	/*
@@ -859,8 +861,8 @@ process_sublinks_mutator(Node *node, bool *isTopQual)
 	 */
 	if (and_clause(node))
 	{
-		List   *newargs = NIL;
-		List   *l;
+		List		*newargs = NIL;
+		ListCell	*l;
 
 		/* Still at qual top-level */
 		locTopQual = *isTopQual;
@@ -884,8 +886,8 @@ process_sublinks_mutator(Node *node, bool *isTopQual)
 
 	if (or_clause(node))
 	{
-		List   *newargs = NIL;
-		List   *l;
+		List		*newargs = NIL;
+		ListCell	*l;
 
 		foreach(l, ((BoolExpr *) node)->args)
 		{
@@ -918,7 +920,7 @@ SS_finalize_plan(Plan *plan, List *rtable)
 	Bitmapset  *outer_params = NULL;
 	Bitmapset  *valid_params = NULL;
 	int			paramid;
-	List	   *lst;
+	ListCell   *l;
 
 	/*
 	 * First, scan the param list to discover the sets of params that are
@@ -926,9 +928,9 @@ SS_finalize_plan(Plan *plan, List *rtable)
 	 * this once to save time in the per-plan recursion steps.
 	 */
 	paramid = 0;
-	foreach(lst, PlannerParamList)
+	foreach(l, PlannerParamList)
 	{
-		PlannerParamItem *pitem = (PlannerParamItem *) lfirst(lst);
+		PlannerParamItem *pitem = (PlannerParamItem *) lfirst(l);
 
 		if (pitem->abslevel < PlannerQueryLevel)
 		{
@@ -966,7 +968,6 @@ finalize_plan(Plan *plan, List *rtable,
 			  Bitmapset *outer_params, Bitmapset *valid_params)
 {
 	finalize_primnode_context context;
-	List	   *lst;
 
 	if (plan == NULL)
 		return NULL;
@@ -1033,14 +1034,18 @@ finalize_plan(Plan *plan, List *rtable,
 			break;
 
 		case T_Append:
-			foreach(lst, ((Append *) plan)->appendplans)
 			{
-				context.paramids =
-					bms_add_members(context.paramids,
-									finalize_plan((Plan *) lfirst(lst),
-												  rtable,
-												  outer_params,
-												  valid_params));
+				ListCell *l;
+
+				foreach(l, ((Append *) plan)->appendplans)
+				{
+					context.paramids =
+						bms_add_members(context.paramids,
+										finalize_plan((Plan *) lfirst(l),
+													  rtable,
+													  outer_params,
+													  valid_params));
+				}
 			}
 			break;