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, 27 deletions

diff --git a/src/backend/optimizer/path/joinrels.c b/src/backend/optimizer/path/joinrels.c
index 07caab48ac6..6debd825c11 100644
--- a/src/backend/optimizer/path/joinrels.c
+++ b/src/backend/optimizer/path/joinrels.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/optimizer/path/joinrels.c,v 1.67 2004/03/08 17:20:17 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/optimizer/path/joinrels.c,v 1.68 2004/05/26 04:41:22 neilc Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -20,10 +20,10 @@
 
 static List *make_rels_by_clause_joins(Query *root,
 						  RelOptInfo *old_rel,
-						  List *other_rels);
+						  ListCell *other_rels);
 static List *make_rels_by_clauseless_joins(Query *root,
 							  RelOptInfo *old_rel,
-							  List *other_rels);
+							  ListCell *other_rels);
 static bool is_inside_IN(Query *root, RelOptInfo *rel);
 
 
@@ -43,8 +43,8 @@ make_rels_by_joins(Query *root, int level, List **joinrels)
 {
 	List	   *result_rels = NIL;
 	List	   *new_rels;
-	List	   *nr;
-	List	   *r;
+	ListCell   *nr;
+	ListCell   *r;
 	int			k;
 
 	/*
@@ -64,13 +64,13 @@ make_rels_by_joins(Query *root, int level, List **joinrels)
 	foreach(r, joinrels[level - 1])
 	{
 		RelOptInfo *old_rel = (RelOptInfo *) lfirst(r);
-		List	   *other_rels;
+		ListCell   *other_rels;
 
 		if (level == 2)
 			other_rels = lnext(r);		/* only consider remaining initial
 										 * rels */
 		else
-			other_rels = joinrels[1];	/* consider all initial rels */
+			other_rels = list_head(joinrels[1]);	/* consider all initial rels */
 
 		if (old_rel->joininfo != NIL)
 		{
@@ -149,8 +149,8 @@ make_rels_by_joins(Query *root, int level, List **joinrels)
 		foreach(r, joinrels[k])
 		{
 			RelOptInfo *old_rel = (RelOptInfo *) lfirst(r);
-			List	   *other_rels;
-			List	   *r2;
+			ListCell   *other_rels;
+			ListCell   *r2;
 
 			if (old_rel->joininfo == NIL)
 				continue;		/* we ignore clauseless joins here */
@@ -158,15 +158,15 @@ make_rels_by_joins(Query *root, int level, List **joinrels)
 			if (k == other_level)
 				other_rels = lnext(r);	/* only consider remaining rels */
 			else
-				other_rels = joinrels[other_level];
+				other_rels = list_head(joinrels[other_level]);
 
-			foreach(r2, other_rels)
+			for_each_cell(r2, other_rels)
 			{
 				RelOptInfo *new_rel = (RelOptInfo *) lfirst(r2);
 
 				if (!bms_overlap(old_rel->relids, new_rel->relids))
 				{
-					List	   *i;
+					ListCell   *i;
 
 					/*
 					 * OK, we can build a rel of the right level from this
@@ -217,14 +217,14 @@ make_rels_by_joins(Query *root, int level, List **joinrels)
 		foreach(r, joinrels[level - 1])
 		{
 			RelOptInfo *old_rel = (RelOptInfo *) lfirst(r);
-			List	   *other_rels;
+			ListCell   *other_rels;
 
 			if (level == 2)
 				other_rels = lnext(r);	/* only consider remaining initial
 										 * rels */
 			else
-				other_rels = joinrels[1];		/* consider all initial
-												 * rels */
+				other_rels = list_head(joinrels[1]); /* consider all initial
+													  * rels */
 
 			new_rels = make_rels_by_clauseless_joins(root,
 													 old_rel,
@@ -271,7 +271,8 @@ make_rels_by_joins(Query *root, int level, List **joinrels)
  *	  The join rel nodes are returned in a list.
  *
  * 'old_rel' is the relation entry for the relation to be joined
- * 'other_rels': other rels to be considered for joining
+ * 'other_rels': the first cell in a linked list containing the other
+ * rels to be considered for joining
  *
  * Currently, this is only used with initial rels in other_rels, but it
  * will work for joining to joinrels too, if the caller ensures there is no
@@ -282,10 +283,10 @@ make_rels_by_joins(Query *root, int level, List **joinrels)
 static List *
 make_rels_by_clause_joins(Query *root,
 						  RelOptInfo *old_rel,
-						  List *other_rels)
+						  ListCell *other_rels)
 {
 	List	   *result = NIL;
-	List	   *i,
+	ListCell   *i,
 			   *j;
 
 	foreach(i, old_rel->joininfo)
@@ -293,7 +294,7 @@ make_rels_by_clause_joins(Query *root,
 		JoinInfo   *joininfo = (JoinInfo *) lfirst(i);
 		Relids		unjoined_relids = joininfo->unjoined_relids;
 
-		foreach(j, other_rels)
+		for_each_cell(j, other_rels)
 		{
 			RelOptInfo *other_rel = (RelOptInfo *) lfirst(j);
 
@@ -324,7 +325,8 @@ make_rels_by_clause_joins(Query *root,
  *	  The join rel nodes are returned in a list.
  *
  * 'old_rel' is the relation entry for the relation to be joined
- * 'other_rels': other rels to be considered for joining
+ * 'other_rels': the first cell of a linked list containing the
+ * other rels to be considered for joining
  *
  * Currently, this is only used with initial rels in other_rels, but it would
  * work for joining to joinrels too.
@@ -332,12 +334,12 @@ make_rels_by_clause_joins(Query *root,
 static List *
 make_rels_by_clauseless_joins(Query *root,
 							  RelOptInfo *old_rel,
-							  List *other_rels)
+							  ListCell *other_rels)
 {
 	List	   *result = NIL;
-	List	   *i;
+	ListCell   *i;
 
-	foreach(i, other_rels)
+	for_each_cell(i, other_rels)
 	{
 		RelOptInfo *other_rel = (RelOptInfo *) lfirst(i);
 
@@ -370,11 +372,11 @@ make_rels_by_clauseless_joins(Query *root,
 static bool
 is_inside_IN(Query *root, RelOptInfo *rel)
 {
-	List	   *i;
+	ListCell   *l;
 
-	foreach(i, root->in_info_list)
+	foreach(l, root->in_info_list)
 	{
-		InClauseInfo *ininfo = (InClauseInfo *) lfirst(i);
+		InClauseInfo *ininfo = (InClauseInfo *) lfirst(l);
 
 		if (bms_is_subset(rel->relids, ininfo->righthand))
 			return true;
@@ -476,7 +478,7 @@ make_join_rel(Query *root, RelOptInfo *rel1, RelOptInfo *rel2,
 	 */
 	if (jointype == JOIN_INNER)
 	{
-		List	   *l;
+		ListCell   *l;
 
 		foreach(l, root->in_info_list)
 		{