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, 64 insertions, 68 deletions

diff --git a/src/backend/optimizer/path/pathkeys.c b/src/backend/optimizer/path/pathkeys.c
index 65eb5cb8a65..af232bd0c98 100644
--- a/src/backend/optimizer/path/pathkeys.c
+++ b/src/backend/optimizer/path/pathkeys.c
@@ -11,7 +11,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/optimizer/path/pathkeys.c,v 1.56 2004/04/07 17:42:28 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/optimizer/path/pathkeys.c,v 1.57 2004/05/26 04:41:22 neilc Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -95,8 +95,8 @@ add_equijoined_keys(Query *root, RestrictInfo *restrictinfo)
 	PathKeyItem *item2 = makePathKeyItem(get_rightop(clause),
 										 restrictinfo->right_sortop,
 										 false);
-	List	   *newset,
-			   *cursetlink;
+	List	   *newset;
+	ListCell   *cursetlink;
 
 	/* We might see a clause X=X; don't make a single-element list from it */
 	if (equal(item1, item2))
@@ -122,10 +122,10 @@ add_equijoined_keys(Query *root, RestrictInfo *restrictinfo)
 	newset = NIL;
 
 	/* cannot use foreach here because of possible lremove */
-	cursetlink = root->equi_key_list;
+	cursetlink = list_head(root->equi_key_list);
 	while (cursetlink)
 	{
-		List	   *curset = lfirst(cursetlink);
+		List	   *curset = (List *) lfirst(cursetlink);
 		bool		item1here = member(item1, curset);
 		bool		item2here = member(item2, curset);
 
@@ -199,15 +199,15 @@ add_equijoined_keys(Query *root, RestrictInfo *restrictinfo)
 void
 generate_implied_equalities(Query *root)
 {
-	List	   *cursetlink;
+	ListCell   *cursetlink;
 
 	foreach(cursetlink, root->equi_key_list)
 	{
-		List	   *curset = lfirst(cursetlink);
+		List	   *curset = (List *) lfirst(cursetlink);
 		int			nitems = length(curset);
 		Relids	   *relids;
 		bool		have_consts;
-		List	   *ptr1;
+		ListCell   *ptr1;
 		int			i1;
 
 		/*
@@ -245,10 +245,10 @@ generate_implied_equalities(Query *root)
 		{
 			PathKeyItem *item1 = (PathKeyItem *) lfirst(ptr1);
 			bool		i1_is_variable = !bms_is_empty(relids[i1]);
-			List	   *ptr2;
+			ListCell   *ptr2;
 			int			i2 = i1 + 1;
 
-			foreach(ptr2, lnext(ptr1))
+			for_each_cell(ptr2, lnext(ptr1))
 			{
 				PathKeyItem *item2 = (PathKeyItem *) lfirst(ptr2);
 				bool		i2_is_variable = !bms_is_empty(relids[i2]);
@@ -294,14 +294,14 @@ generate_implied_equalities(Query *root)
 bool
 exprs_known_equal(Query *root, Node *item1, Node *item2)
 {
-	List	   *cursetlink;
+	ListCell   *cursetlink;
 
 	foreach(cursetlink, root->equi_key_list)
 	{
-		List	   *curset = lfirst(cursetlink);
+		List	   *curset = (List *) lfirst(cursetlink);
 		bool		item1member = false;
 		bool		item2member = false;
-		List	   *ptr;
+		ListCell   *ptr;
 
 		foreach(ptr, curset)
 		{
@@ -334,12 +334,12 @@ exprs_known_equal(Query *root, Node *item1, Node *item2)
 static List *
 make_canonical_pathkey(Query *root, PathKeyItem *item)
 {
-	List	   *cursetlink;
 	List	   *newset;
+	ListCell   *cursetlink;
 
 	foreach(cursetlink, root->equi_key_list)
 	{
-		List	   *curset = lfirst(cursetlink);
+		List	   *curset = (List *) lfirst(cursetlink);
 
 		if (member(item, curset))
 			return curset;
@@ -360,11 +360,11 @@ List *
 canonicalize_pathkeys(Query *root, List *pathkeys)
 {
 	List	   *new_pathkeys = NIL;
-	List	   *i;
+	ListCell   *l;
 
-	foreach(i, pathkeys)
+	foreach(l, pathkeys)
 	{
-		List	   *pathkey = (List *) lfirst(i);
+		List	   *pathkey = (List *) lfirst(l);
 		PathKeyItem *item;
 		List	   *cpathkey;
 
@@ -374,7 +374,7 @@ canonicalize_pathkeys(Query *root, List *pathkeys)
 		 * set by definition.
 		 */
 		Assert(pathkey != NIL);
-		item = (PathKeyItem *) lfirst(pathkey);
+		item = (PathKeyItem *) linitial(pathkey);
 		cpathkey = make_canonical_pathkey(root, item);
 
 		/*
@@ -402,11 +402,11 @@ canonicalize_pathkeys(Query *root, List *pathkeys)
 static int
 count_canonical_peers(Query *root, PathKeyItem *item)
 {
-	List	   *cursetlink;
+	ListCell   *cursetlink;
 
 	foreach(cursetlink, root->equi_key_list)
 	{
-		List	   *curset = lfirst(cursetlink);
+		List	   *curset = (List *) lfirst(cursetlink);
 
 		if (member(item, curset))
 			return length(curset) - 1;
@@ -430,15 +430,13 @@ count_canonical_peers(Query *root, PathKeyItem *item)
 PathKeysComparison
 compare_pathkeys(List *keys1, List *keys2)
 {
-	List	   *key1,
+	ListCell   *key1,
 			   *key2;
 
-	for (key1 = keys1, key2 = keys2;
-		 key1 != NIL && key2 != NIL;
-		 key1 = lnext(key1), key2 = lnext(key2))
+	forboth(key1, keys1, key2, keys2)
 	{
-		List	   *subkey1 = lfirst(key1);
-		List	   *subkey2 = lfirst(key2);
+		List	   *subkey1 = (List *) lfirst(key1);
+		List	   *subkey2 = (List *) lfirst(key2);
 
 		/*
 		 * XXX would like to check that we've been given canonicalized
@@ -465,9 +463,9 @@ compare_pathkeys(List *keys1, List *keys2)
 	 * the other list are not NIL --- no pathkey list should ever have a
 	 * NIL sublist.)
 	 */
-	if (key1 == NIL && key2 == NIL)
+	if (key1 == NULL && key2 == NULL)
 		return PATHKEYS_EQUAL;
-	if (key1 != NIL)
+	if (key1 != NULL)
 		return PATHKEYS_BETTER1;	/* key1 is longer */
 	return PATHKEYS_BETTER2;	/* key2 is longer */
 }
@@ -493,15 +491,13 @@ compare_pathkeys(List *keys1, List *keys2)
 PathKeysComparison
 compare_noncanonical_pathkeys(List *keys1, List *keys2)
 {
-	List	   *key1,
+	ListCell   *key1,
 			   *key2;
 
-	for (key1 = keys1, key2 = keys2;
-		 key1 != NIL && key2 != NIL;
-		 key1 = lnext(key1), key2 = lnext(key2))
+	forboth(key1, keys1, key2, keys2)
 	{
-		List	   *subkey1 = lfirst(key1);
-		List	   *subkey2 = lfirst(key2);
+		List	   *subkey1 = (List *) lfirst(key1);
+		List	   *subkey2 = (List *) lfirst(key2);
 
 		Assert(length(subkey1) == 1);
 		Assert(length(subkey2) == 1);
@@ -515,9 +511,9 @@ compare_noncanonical_pathkeys(List *keys1, List *keys2)
 	 * the other list are not NIL --- no pathkey list should ever have a
 	 * NIL sublist.)
 	 */
-	if (key1 == NIL && key2 == NIL)
+	if (key1 == NULL && key2 == NULL)
 		return PATHKEYS_EQUAL;
-	if (key1 != NIL)
+	if (key1 != NULL)
 		return PATHKEYS_BETTER1;	/* key1 is longer */
 	return PATHKEYS_BETTER2;	/* key2 is longer */
 }
@@ -573,11 +569,11 @@ get_cheapest_path_for_pathkeys(List *paths, List *pathkeys,
 							   CostSelector cost_criterion)
 {
 	Path	   *matched_path = NULL;
-	List	   *i;
+	ListCell   *l;
 
-	foreach(i, paths)
+	foreach(l, paths)
 	{
-		Path	   *path = (Path *) lfirst(i);
+		Path	   *path = (Path *) lfirst(l);
 
 		/*
 		 * Since cost comparison is a lot cheaper than pathkey comparison,
@@ -612,11 +608,11 @@ get_cheapest_fractional_path_for_pathkeys(List *paths,
 										  double fraction)
 {
 	Path	   *matched_path = NULL;
-	List	   *i;
+	ListCell   *l;
 
-	foreach(i, paths)
+	foreach(l, paths)
 	{
-		Path	   *path = (Path *) lfirst(i);
+		Path	   *path = (Path *) lfirst(l);
 
 		/*
 		 * Since cost comparison is a lot cheaper than pathkey comparison,
@@ -658,7 +654,7 @@ build_index_pathkeys(Query *root,
 	List	   *retval = NIL;
 	int		   *indexkeys = index->indexkeys;
 	Oid		   *ordering = index->ordering;
-	List	   *indexprs = index->indexprs;
+	ListCell   *indexprs_item = list_head(index->indexprs);
 
 	while (*ordering != InvalidOid)
 	{
@@ -683,10 +679,10 @@ build_index_pathkeys(Query *root,
 		else
 		{
 			/* expression --- assume we need not copy it */
-			if (indexprs == NIL)
+			if (indexprs_item == NULL)
 				elog(ERROR, "wrong number of index expressions");
-			indexkey = (Node *) lfirst(indexprs);
-			indexprs = lnext(indexprs);
+			indexkey = (Node *) lfirst(indexprs_item);
+			indexprs_item = lnext(indexprs_item);
 		}
 
 		/* OK, make a sublist for this sort key */
@@ -719,7 +715,7 @@ build_index_pathkeys(Query *root,
 static Var *
 find_indexkey_var(Query *root, RelOptInfo *rel, AttrNumber varattno)
 {
-	List	   *temp;
+	ListCell   *temp;
 	Index		relid;
 	Oid			reloid,
 				vartypeid;
@@ -758,12 +754,12 @@ build_subquery_pathkeys(Query *root, RelOptInfo *rel, Query *subquery)
 	int			retvallen = 0;
 	int			outer_query_keys = length(root->query_pathkeys);
 	List	   *sub_tlist = rel->subplan->targetlist;
-	List	   *l;
+	ListCell   *i;
 
-	foreach(l, subquery->query_pathkeys)
+	foreach(i, subquery->query_pathkeys)
 	{
-		List	   *sub_pathkey = (List *) lfirst(l);
-		List	   *j;
+		List	   *sub_pathkey = (List *) lfirst(i);
+		ListCell   *j;
 		PathKeyItem *best_item = NULL;
 		int			best_score = 0;
 		List	   *cpathkey;
@@ -788,7 +784,7 @@ build_subquery_pathkeys(Query *root, RelOptInfo *rel, Query *subquery)
 		{
 			PathKeyItem *sub_item = (PathKeyItem *) lfirst(j);
 			Node	   *sub_key = sub_item->key;
-			List	   *k;
+			ListCell   *k;
 
 			foreach(k, sub_tlist)
 			{
@@ -908,11 +904,11 @@ make_pathkeys_for_sortclauses(List *sortclauses,
 							  List *tlist)
 {
 	List	   *pathkeys = NIL;
-	List	   *i;
+	ListCell   *l;
 
-	foreach(i, sortclauses)
+	foreach(l, sortclauses)
 	{
-		SortClause *sortcl = (SortClause *) lfirst(i);
+		SortClause *sortcl = (SortClause *) lfirst(l);
 		Node	   *sortkey;
 		PathKeyItem *pathkey;
 
@@ -1000,21 +996,21 @@ find_mergeclauses_for_pathkeys(Query *root,
 							   List *restrictinfos)
 {
 	List	   *mergeclauses = NIL;
-	List	   *i;
+	ListCell   *i;
 
 	/* make sure we have pathkeys cached in the clauses */
 	foreach(i, restrictinfos)
 	{
-		RestrictInfo *restrictinfo = lfirst(i);
+		RestrictInfo *restrictinfo = (RestrictInfo *) lfirst(i);
 
 		cache_mergeclause_pathkeys(root, restrictinfo);
 	}
 
 	foreach(i, pathkeys)
 	{
-		List	   *pathkey = lfirst(i);
+		List	   *pathkey = (List *) lfirst(i);
 		List	   *matched_restrictinfos = NIL;
-		List	   *j;
+		ListCell   *j;
 
 		/*
 		 * We can match a pathkey against either left or right side of any
@@ -1037,7 +1033,7 @@ find_mergeclauses_for_pathkeys(Query *root,
 		 */
 		foreach(j, restrictinfos)
 		{
-			RestrictInfo *restrictinfo = lfirst(j);
+			RestrictInfo *restrictinfo = (RestrictInfo *) lfirst(j);
 
 			/*
 			 * We can compare canonical pathkey sublists by simple pointer
@@ -1093,11 +1089,11 @@ make_pathkeys_for_mergeclauses(Query *root,
 							   RelOptInfo *rel)
 {
 	List	   *pathkeys = NIL;
-	List	   *i;
+	ListCell   *l;
 
-	foreach(i, mergeclauses)
+	foreach(l, mergeclauses)
 	{
-		RestrictInfo *restrictinfo = (RestrictInfo *) lfirst(i);
+		RestrictInfo *restrictinfo = (RestrictInfo *) lfirst(l);
 		List	   *pathkey;
 
 		cache_mergeclause_pathkeys(root, restrictinfo);
@@ -1160,18 +1156,18 @@ int
 pathkeys_useful_for_merging(Query *root, RelOptInfo *rel, List *pathkeys)
 {
 	int			useful = 0;
-	List	   *i;
+	ListCell   *i;
 
 	foreach(i, pathkeys)
 	{
-		List	   *pathkey = lfirst(i);
+		List	   *pathkey = (List *) lfirst(i);
 		bool		matched = false;
-		List	   *j;
+		ListCell   *j;
 
 		foreach(j, rel->joininfo)
 		{
 			JoinInfo   *joininfo = (JoinInfo *) lfirst(j);
-			List	   *k;
+			ListCell   *k;
 
 			foreach(k, joininfo->jinfo_restrictinfo)
 			{