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, 15 insertions, 15 deletions

diff --git a/src/backend/utils/adt/selfuncs.c b/src/backend/utils/adt/selfuncs.c
index ded7260c784..cd9a6444d41 100644
--- a/src/backend/utils/adt/selfuncs.c
+++ b/src/backend/utils/adt/selfuncs.c
@@ -15,7 +15,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/utils/adt/selfuncs.c,v 1.158 2004/02/27 21:44:34 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/utils/adt/selfuncs.c,v 1.159 2004/05/26 04:41:39 neilc Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -1936,7 +1936,7 @@ estimate_num_groups(Query *root, List *groupExprs, double input_rows)
 	List	   *allvars = NIL;
 	List	   *varinfos = NIL;
 	double		numdistinct;
-	List	   *l;
+	ListCell   *l;
 	typedef struct
 	{							/* varinfos is a List of these */
 		Var		   *var;
@@ -1987,14 +1987,14 @@ estimate_num_groups(Query *root, List *groupExprs, double input_rows)
 		VariableStatData vardata;
 		double		ndistinct;
 		bool		keep = true;
-		List	   *l2;
+		ListCell   *l2;
 
 		examine_variable(root, (Node *) var, 0, &vardata);
 		ndistinct = get_variable_numdistinct(&vardata);
 		ReleaseVariableStats(vardata);
 
 		/* cannot use foreach here because of possible lremove */
-		l2 = varinfos;
+		l2 = list_head(varinfos);
 		while (l2)
 		{
 			MyVarInfo  *varinfo = (MyVarInfo *) lfirst(l2);
@@ -2043,7 +2043,7 @@ estimate_num_groups(Query *root, List *groupExprs, double input_rows)
 
 	do
 	{
-		MyVarInfo  *varinfo1 = (MyVarInfo *) lfirst(varinfos);
+		MyVarInfo  *varinfo1 = (MyVarInfo *) linitial(varinfos);
 		RelOptInfo *rel = find_base_rel(root, varinfo1->var->varno);
 		double		reldistinct = varinfo1->ndistinct;
 		List	   *newvarinfos = NIL;
@@ -2052,7 +2052,7 @@ estimate_num_groups(Query *root, List *groupExprs, double input_rows)
 		 * Get the largest numdistinct estimate of the Vars for this rel.
 		 * Also, construct new varinfos list of remaining Vars.
 		 */
-		foreach(l, lnext(varinfos))
+		for_each_cell(l, lnext(list_head(varinfos)))
 		{
 			MyVarInfo  *varinfo2 = (MyVarInfo *) lfirst(l);
 
@@ -2844,7 +2844,7 @@ get_restriction_variable(Query *root, List *args, int varRelid,
 	if (length(args) != 2)
 		return false;
 
-	left = (Node *) lfirst(args);
+	left = (Node *) linitial(args);
 	right = (Node *) lsecond(args);
 
 	/*
@@ -2895,7 +2895,7 @@ get_join_variables(Query *root, List *args,
 	if (length(args) != 2)
 		elog(ERROR, "join operator should take two arguments");
 
-	left = (Node *) lfirst(args);
+	left = (Node *) linitial(args);
 	right = (Node *) lsecond(args);
 
 	examine_variable(root, left, 0, vardata1);
@@ -3033,16 +3033,16 @@ examine_variable(Query *root, Node *node, int varRelid,
 		 * different index opclasses; if so, we need to pick one that
 		 * matches the operator we are estimating for.  FIXME later.
 		 */
-		List	   *ilist;
+		ListCell   *ilist;
 
 		foreach(ilist, onerel->indexlist)
 		{
 			IndexOptInfo *index = (IndexOptInfo *) lfirst(ilist);
-			List	   *indexprs;
+			ListCell   *indexpr_item;
 			int			pos;
 
-			indexprs = index->indexprs;
-			if (indexprs == NIL)
+			indexpr_item = list_head(index->indexprs);
+			if (indexpr_item == NULL)
 				continue;		/* no expressions here... */
 
 			/*
@@ -3058,9 +3058,9 @@ examine_variable(Query *root, Node *node, int varRelid,
 				{
 					Node	   *indexkey;
 
-					if (indexprs == NIL)
+					if (indexpr_item == NULL)
 						elog(ERROR, "too few entries in indexprs list");
-					indexkey = (Node *) lfirst(indexprs);
+					indexkey = (Node *) lfirst(indexpr_item);
 					if (indexkey && IsA(indexkey, RelabelType))
 						indexkey = (Node *) ((RelabelType *) indexkey)->arg;
 					if (equal(node, indexkey))
@@ -3081,7 +3081,7 @@ examine_variable(Query *root, Node *node, int varRelid,
 						if (vardata->statsTuple)
 							break;
 					}
-					indexprs = lnext(indexprs);
+					indexpr_item = lnext(indexpr_item);
 				}
 			}
 			if (vardata->statsTuple)