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, 26 insertions, 25 deletions

diff --git a/src/backend/optimizer/path/allpaths.c b/src/backend/optimizer/path/allpaths.c
index 217f06a6b2b..a4bc92b1c3b 100644
--- a/src/backend/optimizer/path/allpaths.c
+++ b/src/backend/optimizer/path/allpaths.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/optimizer/path/allpaths.c,v 1.114 2004/05/10 22:44:44 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/optimizer/path/allpaths.c,v 1.115 2004/05/26 04:41:21 neilc Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -102,11 +102,11 @@ make_one_rel(Query *root)
 static void
 set_base_rel_pathlists(Query *root)
 {
-	List	   *rellist;
+	ListCell	   *l;
 
-	foreach(rellist, root->base_rel_list)
+	foreach(l, root->base_rel_list)
 	{
-		RelOptInfo *rel = (RelOptInfo *) lfirst(rellist);
+		RelOptInfo *rel = (RelOptInfo *) lfirst(l);
 		Index		rti = rel->relid;
 		RangeTblEntry *rte;
 		List	   *inheritlist;
@@ -212,7 +212,7 @@ set_inherited_rel_pathlist(Query *root, RelOptInfo *rel,
 	int			parentRTindex = rti;
 	Oid			parentOID = rte->relid;
 	List	   *subpaths = NIL;
-	List	   *il;
+	ListCell   *il;
 
 	/*
 	 * XXX for now, can't handle inherited expansion of FOR UPDATE; can we
@@ -247,8 +247,8 @@ set_inherited_rel_pathlist(Query *root, RelOptInfo *rel,
 		Oid			childOID;
 		RelOptInfo *childrel;
 		List	   *reltlist;
-		List	   *parentvars;
-		List	   *childvars;
+		ListCell   *parentvars;
+		ListCell   *childvars;
 
 		childrte = rt_fetch(childRTindex, root->rtable);
 		childOID = childrte->relid;
@@ -300,7 +300,7 @@ set_inherited_rel_pathlist(Query *root, RelOptInfo *rel,
 		if (childrel->width > rel->width)
 			rel->width = childrel->width;
 
-		childvars = FastListValue(&childrel->reltargetlist);
+		childvars = list_head(FastListValue(&childrel->reltargetlist));
 		foreach(parentvars, FastListValue(&rel->reltargetlist))
 		{
 			Var		   *parentvar = (Var *) lfirst(parentvars);
@@ -366,11 +366,11 @@ set_subquery_pathlist(Query *root, RelOptInfo *rel,
 	{
 		/* OK to consider pushing down individual quals */
 		List	   *upperrestrictlist = NIL;
-		List	   *lst;
+		ListCell   *l;
 
-		foreach(lst, rel->baserestrictinfo)
+		foreach(l, rel->baserestrictinfo)
 		{
-			RestrictInfo *rinfo = (RestrictInfo *) lfirst(lst);
+			RestrictInfo *rinfo = (RestrictInfo *) lfirst(l);
 			Node	   *clause = (Node *) rinfo->clause;
 
 			if (qual_is_pushdown_safe(subquery, rti, clause, differentTypes))
@@ -434,7 +434,7 @@ make_fromexpr_rel(Query *root, FromExpr *from)
 {
 	int			levels_needed;
 	List	   *initial_rels = NIL;
-	List	   *jt;
+	ListCell   *jt;
 
 	/*
 	 * Count the number of child jointree nodes.  This is the depth of the
@@ -464,7 +464,7 @@ make_fromexpr_rel(Query *root, FromExpr *from)
 		/*
 		 * Single jointree node, so we're done.
 		 */
-		return (RelOptInfo *) lfirst(initial_rels);
+		return (RelOptInfo *) linitial(initial_rels);
 	}
 	else
 	{
@@ -516,7 +516,7 @@ make_one_rel_by_joins(Query *root, int levels_needed, List *initial_rels)
 
 	for (lev = 2; lev <= levels_needed; lev++)
 	{
-		List	   *x;
+		ListCell   *x;
 
 		/*
 		 * Determine all possible pairs of relations to be joined at this
@@ -548,7 +548,7 @@ make_one_rel_by_joins(Query *root, int levels_needed, List *initial_rels)
 		elog(ERROR, "failed to build any %d-way joins", levels_needed);
 	Assert(length(joinitems[levels_needed]) == 1);
 
-	rel = (RelOptInfo *) lfirst(joinitems[levels_needed]);
+	rel = (RelOptInfo *) linitial(joinitems[levels_needed]);
 
 	return rel;
 }
@@ -660,21 +660,22 @@ static void
 compare_tlist_datatypes(List *tlist, List *colTypes,
 						bool *differentTypes)
 {
-	List	   *i;
+	ListCell   *l;
+	ListCell   *colType = list_head(colTypes);
 
-	foreach(i, tlist)
+	foreach(l, tlist)
 	{
-		TargetEntry *tle = (TargetEntry *) lfirst(i);
+		TargetEntry *tle = (TargetEntry *) lfirst(l);
 
 		if (tle->resdom->resjunk)
 			continue;			/* ignore resjunk columns */
-		if (colTypes == NIL)
+		if (colType == NULL)
 			elog(ERROR, "wrong number of tlist entries");
-		if (tle->resdom->restype != lfirsto(colTypes))
+		if (tle->resdom->restype != lfirst_oid(colType))
 			differentTypes[tle->resdom->resno] = true;
-		colTypes = lnext(colTypes);
+		colType = lnext(colType);
 	}
-	if (colTypes != NIL)
+	if (colType != NULL)
 		elog(ERROR, "wrong number of tlist entries");
 }
 
@@ -712,7 +713,7 @@ qual_is_pushdown_safe(Query *subquery, Index rti, Node *qual,
 {
 	bool		safe = true;
 	List	   *vars;
-	List	   *vl;
+	ListCell   *vl;
 	Bitmapset  *tested = NULL;
 
 	/* Refuse subselects (point 1) */
@@ -869,7 +870,7 @@ print_relids(Relids relids)
 static void
 print_restrictclauses(Query *root, List *clauses)
 {
-	List	   *l;
+	ListCell   *l;
 
 	foreach(l, clauses)
 	{
@@ -987,7 +988,7 @@ print_path(Query *root, Path *path, int indent)
 void
 debug_print_rel(Query *root, RelOptInfo *rel)
 {
-	List	   *l;
+	ListCell   *l;
 
 	printf("RELOPTINFO (");
 	print_relids(rel->relids);