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, 25 insertions, 25 deletions

diff --git a/src/backend/optimizer/prep/prepqual.c b/src/backend/optimizer/prep/prepqual.c
index ac107aade61..1cfafe5452b 100644
--- a/src/backend/optimizer/prep/prepqual.c
+++ b/src/backend/optimizer/prep/prepqual.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/optimizer/prep/prepqual.c,v 1.41 2003/12/30 21:49:19 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/optimizer/prep/prepqual.c,v 1.42 2004/05/26 04:41:26 neilc Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -144,7 +144,7 @@ flatten_andors_mutator(Node *node, void *context)
 static void
 flatten_andors_and_walker(FastList *out_list, List *andlist)
 {
-	List	   *arg;
+	ListCell   *arg;
 
 	foreach(arg, andlist)
 	{
@@ -160,7 +160,7 @@ flatten_andors_and_walker(FastList *out_list, List *andlist)
 static void
 flatten_andors_or_walker(FastList *out_list, List *orlist)
 {
-	List	   *arg;
+	ListCell   *arg;
 
 	foreach(arg, orlist)
 	{
@@ -193,7 +193,7 @@ pull_ands(List *andlist)
 static void
 pull_ands_walker(FastList *out_list, List *andlist)
 {
-	List	   *arg;
+	ListCell   *arg;
 
 	foreach(arg, andlist)
 	{
@@ -226,7 +226,7 @@ pull_ors(List *orlist)
 static void
 pull_ors_walker(FastList *out_list, List *orlist)
 {
-	List	   *arg;
+	ListCell   *arg;
 
 	foreach(arg, orlist)
 	{
@@ -258,7 +258,7 @@ find_nots(Expr *qual)
 	if (and_clause((Node *) qual))
 	{
 		FastList	t_list;
-		List	   *temp;
+		ListCell   *temp;
 
 		FastListInit(&t_list);
 		foreach(temp, ((BoolExpr *) qual)->args)
@@ -268,7 +268,7 @@ find_nots(Expr *qual)
 	else if (or_clause((Node *) qual))
 	{
 		FastList	t_list;
-		List	   *temp;
+		ListCell   *temp;
 
 		FastListInit(&t_list);
 		foreach(temp, ((BoolExpr *) qual)->args)
@@ -324,7 +324,7 @@ push_nots(Expr *qual)
 		 *--------------------
 		 */
 		FastList	t_list;
-		List	   *temp;
+		ListCell   *temp;
 
 		FastListInit(&t_list);
 		foreach(temp, ((BoolExpr *) qual)->args)
@@ -334,7 +334,7 @@ push_nots(Expr *qual)
 	else if (or_clause((Node *) qual))
 	{
 		FastList	t_list;
-		List	   *temp;
+		ListCell   *temp;
 
 		FastListInit(&t_list);
 		foreach(temp, ((BoolExpr *) qual)->args)
@@ -398,7 +398,7 @@ find_duplicate_ors(Expr *qual)
 	if (or_clause((Node *) qual))
 	{
 		List	   *orlist = NIL;
-		List	   *temp;
+		ListCell   *temp;
 
 		/* Recurse */
 		foreach(temp, ((BoolExpr *) qual)->args)
@@ -412,7 +412,7 @@ find_duplicate_ors(Expr *qual)
 	else if (and_clause((Node *) qual))
 	{
 		List	   *andlist = NIL;
-		List	   *temp;
+		ListCell   *temp;
 
 		/* Recurse */
 		foreach(temp, ((BoolExpr *) qual)->args)
@@ -441,13 +441,12 @@ process_duplicate_ors(List *orlist)
 	int			num_subclauses = 0;
 	List	   *winners;
 	List	   *neworlist;
-	List	   *temp;
-	List	   *temp2;
+	ListCell   *temp;
 
 	if (orlist == NIL)
 		return NULL;			/* probably can't happen */
-	if (lnext(orlist) == NIL)
-		return lfirst(orlist);	/* single-expression OR (can this happen?) */
+	if (length(orlist) == 1)	/* single-expression OR (can this happen?) */
+		return linitial(orlist);
 
 	/*
 	 * Choose the shortest AND clause as the reference list --- obviously,
@@ -457,7 +456,7 @@ process_duplicate_ors(List *orlist)
 	 */
 	foreach(temp, orlist)
 	{
-		Expr	   *clause = lfirst(temp);
+		Expr	   *clause = (Expr *) lfirst(temp);
 
 		if (and_clause((Node *) clause))
 		{
@@ -489,12 +488,13 @@ process_duplicate_ors(List *orlist)
 	winners = NIL;
 	foreach(temp, reference)
 	{
-		Expr	   *refclause = lfirst(temp);
+		Expr	   *refclause = (Expr *) lfirst(temp);
 		bool		win = true;
+		ListCell   *temp2;
 
 		foreach(temp2, orlist)
 		{
-			Expr	   *clause = lfirst(temp2);
+			Expr	   *clause = (Expr *) lfirst(temp2);
 
 			if (and_clause((Node *) clause))
 			{
@@ -537,7 +537,7 @@ process_duplicate_ors(List *orlist)
 	neworlist = NIL;
 	foreach(temp, orlist)
 	{
-		Expr	   *clause = lfirst(temp);
+		Expr	   *clause = (Expr *) lfirst(temp);
 
 		if (and_clause((Node *) clause))
 		{
@@ -546,8 +546,8 @@ process_duplicate_ors(List *orlist)
 			subclauses = set_difference(subclauses, winners);
 			if (subclauses != NIL)
 			{
-				if (lnext(subclauses) == NIL)
-					neworlist = lappend(neworlist, lfirst(subclauses));
+				if (length(subclauses) == 1)
+					neworlist = lappend(neworlist, linitial(subclauses));
 				else
 					neworlist = lappend(neworlist, make_andclause(subclauses));
 			}
@@ -577,8 +577,8 @@ process_duplicate_ors(List *orlist)
 	 */
 	if (neworlist != NIL)
 	{
-		if (lnext(neworlist) == NIL)
-			winners = lappend(winners, lfirst(neworlist));
+		if (length(neworlist) == 1)
+			winners = lappend(winners, linitial(neworlist));
 		else
 			winners = lappend(winners, make_orclause(pull_ors(neworlist)));
 	}
@@ -587,8 +587,8 @@ process_duplicate_ors(List *orlist)
 	 * And return the constructed AND clause, again being wary of a single
 	 * element and AND/OR flatness.
 	 */
-	if (lnext(winners) == NIL)
-		return (Expr *) lfirst(winners);
+	if (length(winners) == 1)
+		return (Expr *) linitial(winners);
 	else
 		return make_andclause(pull_ands(winners));
 }