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, 29 insertions, 21 deletions

diff --git a/src/backend/optimizer/prep/prepjointree.c b/src/backend/optimizer/prep/prepjointree.c
index 0ddf1ccd67f..f916d54602d 100644
--- a/src/backend/optimizer/prep/prepjointree.c
+++ b/src/backend/optimizer/prep/prepjointree.c
@@ -16,7 +16,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/optimizer/prep/prepjointree.c,v 1.17 2004/05/10 22:44:45 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/optimizer/prep/prepjointree.c,v 1.18 2004/05/26 04:41:26 neilc Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -97,11 +97,11 @@ pull_up_IN_clauses(Query *parse, Node *node)
 	if (and_clause(node))
 	{
 		List	   *newclauses = NIL;
-		List	   *oldclauses;
+		ListCell   *l;
 
-		foreach(oldclauses, ((BoolExpr *) node)->args)
+		foreach(l, ((BoolExpr *) node)->args)
 		{
-			Node	   *oldclause = lfirst(oldclauses);
+			Node	   *oldclause = (Node *) lfirst(l);
 
 			newclauses = lappend(newclauses,
 								 pull_up_IN_clauses(parse,
@@ -162,7 +162,7 @@ pull_up_subqueries(Query *parse, Node *jtnode, bool below_outer_join)
 		{
 			int			rtoffset;
 			List	   *subtlist;
-			List	   *rt;
+			ListCell   *rt;
 
 			/*
 			 * Need a modifiable copy of the subquery to hack on.  Even if
@@ -314,7 +314,7 @@ pull_up_subqueries(Query *parse, Node *jtnode, bool below_outer_join)
 	else if (IsA(jtnode, FromExpr))
 	{
 		FromExpr   *f = (FromExpr *) jtnode;
-		List	   *l;
+		ListCell   *l;
 
 		foreach(l, f->fromlist)
 			lfirst(l) = pull_up_subqueries(parse, lfirst(l),
@@ -447,7 +447,7 @@ is_simple_subquery(Query *subquery)
 static bool
 has_nullable_targetlist(Query *subquery)
 {
-	List	   *l;
+	ListCell   *l;
 
 	foreach(l, subquery->targetList)
 	{
@@ -488,7 +488,7 @@ resolvenew_in_jointree(Node *jtnode, int varno,
 	else if (IsA(jtnode, FromExpr))
 	{
 		FromExpr   *f = (FromExpr *) jtnode;
-		List	   *l;
+		ListCell   *l;
 
 		foreach(l, f->fromlist)
 			resolvenew_in_jointree(lfirst(l), varno, rte, subtlist);
@@ -588,7 +588,7 @@ reduce_outer_joins_pass1(Node *jtnode)
 	else if (IsA(jtnode, FromExpr))
 	{
 		FromExpr   *f = (FromExpr *) jtnode;
-		List	   *l;
+		ListCell   *l;
 
 		foreach(l, f->fromlist)
 		{
@@ -653,8 +653,8 @@ reduce_outer_joins_pass2(Node *jtnode,
 	else if (IsA(jtnode, FromExpr))
 	{
 		FromExpr   *f = (FromExpr *) jtnode;
-		List	   *l;
-		List	   *s;
+		ListCell   *l;
+		ListCell   *s;
 		Relids		pass_nonnullable;
 
 		/* Scan quals to see if we can add any nonnullability constraints */
@@ -662,15 +662,14 @@ reduce_outer_joins_pass2(Node *jtnode,
 		pass_nonnullable = bms_add_members(pass_nonnullable,
 										   nonnullable_rels);
 		/* And recurse --- but only into interesting subtrees */
-		s = state->sub_states;
-		foreach(l, f->fromlist)
+		Assert(length(f->fromlist) == length(state->sub_states));
+		forboth(l, f->fromlist, s, state->sub_states)
 		{
 			reduce_outer_joins_state *sub_state = lfirst(s);
 
 			if (sub_state->contains_outer)
 				reduce_outer_joins_pass2(lfirst(l), sub_state, parse,
 										 pass_nonnullable);
-			s = lnext(s);
 		}
 		bms_free(pass_nonnullable);
 	}
@@ -679,7 +678,7 @@ reduce_outer_joins_pass2(Node *jtnode,
 		JoinExpr   *j = (JoinExpr *) jtnode;
 		int			rtindex = j->rtindex;
 		JoinType	jointype = j->jointype;
-		reduce_outer_joins_state *left_state = lfirst(state->sub_states);
+		reduce_outer_joins_state *left_state = linitial(state->sub_states);
 		reduce_outer_joins_state *right_state = lsecond(state->sub_states);
 
 		/* Can we simplify this join? */
@@ -798,7 +797,7 @@ find_nonnullable_rels(Node *node, bool top_level)
 	}
 	else if (IsA(node, List))
 	{
-		List	   *l;
+		ListCell   *l;
 
 		foreach(l, (List *) node)
 		{
@@ -898,7 +897,7 @@ simplify_jointree(Query *parse, Node *jtnode)
 	{
 		FromExpr   *f = (FromExpr *) jtnode;
 		List	   *newlist = NIL;
-		List	   *l;
+		ListCell   *l;
 
 		foreach(l, f->fromlist)
 		{
@@ -918,7 +917,16 @@ simplify_jointree(Query *parse, Node *jtnode)
 				 */
 				FromExpr   *subf = (FromExpr *) child;
 				int			childlen = length(subf->fromlist);
-				int			myothers = length(newlist) + length(lnext(l));
+				int			myothers;
+				ListCell   *l2;
+
+				/*
+				 * XXX: This is a quick hack, not sure of the proper
+				 * fix.
+				 */
+				myothers = length(newlist);
+				for_each_cell(l2, lnext(l))
+					myothers++;
 
 				if (childlen <= 1 ||
 					(childlen + myothers) <= from_collapse_limit)
@@ -1022,7 +1030,7 @@ simplify_jointree(Query *parse, Node *jtnode)
 static void
 fix_in_clause_relids(List *in_info_list, int varno, Relids subrelids)
 {
-	List	   *l;
+	ListCell   *l;
 
 	foreach(l, in_info_list)
 	{
@@ -1060,7 +1068,7 @@ get_relids_in_jointree(Node *jtnode)
 	else if (IsA(jtnode, FromExpr))
 	{
 		FromExpr   *f = (FromExpr *) jtnode;
-		List	   *l;
+		ListCell   *l;
 
 		foreach(l, f->fromlist)
 		{
@@ -1119,7 +1127,7 @@ find_jointree_node_for_rel(Node *jtnode, int relid)
 	else if (IsA(jtnode, FromExpr))
 	{
 		FromExpr   *f = (FromExpr *) jtnode;
-		List	   *l;
+		ListCell   *l;
 
 		foreach(l, f->fromlist)
 		{