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.

4 files changed, 98 insertions, 82 deletions

diff --git a/src/backend/optimizer/prep/prepjointree.c b/src/backend/optimizer/prep/prepjointree.c
index 0ddf1ccd67f..f916d54602d 100644
--- a/src/backend/optimizer/prep/prepjointree.c
+++ b/src/backend/optimizer/prep/prepjointree.c
@@ -16,7 +16,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/optimizer/prep/prepjointree.c,v 1.17 2004/05/10 22:44:45 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/optimizer/prep/prepjointree.c,v 1.18 2004/05/26 04:41:26 neilc Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -97,11 +97,11 @@ pull_up_IN_clauses(Query *parse, Node *node)
 	if (and_clause(node))
 	{
 		List	   *newclauses = NIL;
-		List	   *oldclauses;
+		ListCell   *l;
 
-		foreach(oldclauses, ((BoolExpr *) node)->args)
+		foreach(l, ((BoolExpr *) node)->args)
 		{
-			Node	   *oldclause = lfirst(oldclauses);
+			Node	   *oldclause = (Node *) lfirst(l);
 
 			newclauses = lappend(newclauses,
 								 pull_up_IN_clauses(parse,
@@ -162,7 +162,7 @@ pull_up_subqueries(Query *parse, Node *jtnode, bool below_outer_join)
 		{
 			int			rtoffset;
 			List	   *subtlist;
-			List	   *rt;
+			ListCell   *rt;
 
 			/*
 			 * Need a modifiable copy of the subquery to hack on.  Even if
@@ -314,7 +314,7 @@ pull_up_subqueries(Query *parse, Node *jtnode, bool below_outer_join)
 	else if (IsA(jtnode, FromExpr))
 	{
 		FromExpr   *f = (FromExpr *) jtnode;
-		List	   *l;
+		ListCell   *l;
 
 		foreach(l, f->fromlist)
 			lfirst(l) = pull_up_subqueries(parse, lfirst(l),
@@ -447,7 +447,7 @@ is_simple_subquery(Query *subquery)
 static bool
 has_nullable_targetlist(Query *subquery)
 {
-	List	   *l;
+	ListCell   *l;
 
 	foreach(l, subquery->targetList)
 	{
@@ -488,7 +488,7 @@ resolvenew_in_jointree(Node *jtnode, int varno,
 	else if (IsA(jtnode, FromExpr))
 	{
 		FromExpr   *f = (FromExpr *) jtnode;
-		List	   *l;
+		ListCell   *l;
 
 		foreach(l, f->fromlist)
 			resolvenew_in_jointree(lfirst(l), varno, rte, subtlist);
@@ -588,7 +588,7 @@ reduce_outer_joins_pass1(Node *jtnode)
 	else if (IsA(jtnode, FromExpr))
 	{
 		FromExpr   *f = (FromExpr *) jtnode;
-		List	   *l;
+		ListCell   *l;
 
 		foreach(l, f->fromlist)
 		{
@@ -653,8 +653,8 @@ reduce_outer_joins_pass2(Node *jtnode,
 	else if (IsA(jtnode, FromExpr))
 	{
 		FromExpr   *f = (FromExpr *) jtnode;
-		List	   *l;
-		List	   *s;
+		ListCell   *l;
+		ListCell   *s;
 		Relids		pass_nonnullable;
 
 		/* Scan quals to see if we can add any nonnullability constraints */
@@ -662,15 +662,14 @@ reduce_outer_joins_pass2(Node *jtnode,
 		pass_nonnullable = bms_add_members(pass_nonnullable,
 										   nonnullable_rels);
 		/* And recurse --- but only into interesting subtrees */
-		s = state->sub_states;
-		foreach(l, f->fromlist)
+		Assert(length(f->fromlist) == length(state->sub_states));
+		forboth(l, f->fromlist, s, state->sub_states)
 		{
 			reduce_outer_joins_state *sub_state = lfirst(s);
 
 			if (sub_state->contains_outer)
 				reduce_outer_joins_pass2(lfirst(l), sub_state, parse,
 										 pass_nonnullable);
-			s = lnext(s);
 		}
 		bms_free(pass_nonnullable);
 	}
@@ -679,7 +678,7 @@ reduce_outer_joins_pass2(Node *jtnode,
 		JoinExpr   *j = (JoinExpr *) jtnode;
 		int			rtindex = j->rtindex;
 		JoinType	jointype = j->jointype;
-		reduce_outer_joins_state *left_state = lfirst(state->sub_states);
+		reduce_outer_joins_state *left_state = linitial(state->sub_states);
 		reduce_outer_joins_state *right_state = lsecond(state->sub_states);
 
 		/* Can we simplify this join? */
@@ -798,7 +797,7 @@ find_nonnullable_rels(Node *node, bool top_level)
 	}
 	else if (IsA(node, List))
 	{
-		List	   *l;
+		ListCell   *l;
 
 		foreach(l, (List *) node)
 		{
@@ -898,7 +897,7 @@ simplify_jointree(Query *parse, Node *jtnode)
 	{
 		FromExpr   *f = (FromExpr *) jtnode;
 		List	   *newlist = NIL;
-		List	   *l;
+		ListCell   *l;
 
 		foreach(l, f->fromlist)
 		{
@@ -918,7 +917,16 @@ simplify_jointree(Query *parse, Node *jtnode)
 				 */
 				FromExpr   *subf = (FromExpr *) child;
 				int			childlen = length(subf->fromlist);
-				int			myothers = length(newlist) + length(lnext(l));
+				int			myothers;
+				ListCell   *l2;
+
+				/*
+				 * XXX: This is a quick hack, not sure of the proper
+				 * fix.
+				 */
+				myothers = length(newlist);
+				for_each_cell(l2, lnext(l))
+					myothers++;
 
 				if (childlen <= 1 ||
 					(childlen + myothers) <= from_collapse_limit)
@@ -1022,7 +1030,7 @@ simplify_jointree(Query *parse, Node *jtnode)
 static void
 fix_in_clause_relids(List *in_info_list, int varno, Relids subrelids)
 {
-	List	   *l;
+	ListCell   *l;
 
 	foreach(l, in_info_list)
 	{
@@ -1060,7 +1068,7 @@ get_relids_in_jointree(Node *jtnode)
 	else if (IsA(jtnode, FromExpr))
 	{
 		FromExpr   *f = (FromExpr *) jtnode;
-		List	   *l;
+		ListCell   *l;
 
 		foreach(l, f->fromlist)
 		{
@@ -1119,7 +1127,7 @@ find_jointree_node_for_rel(Node *jtnode, int relid)
 	else if (IsA(jtnode, FromExpr))
 	{
 		FromExpr   *f = (FromExpr *) jtnode;
-		List	   *l;
+		ListCell   *l;
 
 		foreach(l, f->fromlist)
 		{
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));
 }
diff --git a/src/backend/optimizer/prep/preptlist.c b/src/backend/optimizer/prep/preptlist.c
index 86a14cacd80..89df7bca35a 100644
--- a/src/backend/optimizer/prep/preptlist.c
+++ b/src/backend/optimizer/prep/preptlist.c
@@ -15,7 +15,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/optimizer/prep/preptlist.c,v 1.66 2003/11/29 19:51:51 pgsql Exp $
+ *	  $PostgreSQL: pgsql/src/backend/optimizer/prep/preptlist.c,v 1.67 2004/05/26 04:41:26 neilc Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -122,10 +122,13 @@ expand_targetlist(List *tlist, int command_type,
 				  Index result_relation, List *range_table)
 {
 	List	   *new_tlist = NIL;
+	ListCell   *tlist_item;
 	Relation	rel;
 	int			attrno,
 				numattrs;
 
+	tlist_item = list_head(tlist);
+
 	/*
 	 * The rewriter should have already ensured that the TLEs are in
 	 * correct order; but we have to insert TLEs for any missing
@@ -143,15 +146,15 @@ expand_targetlist(List *tlist, int command_type,
 		Form_pg_attribute att_tup = rel->rd_att->attrs[attrno - 1];
 		TargetEntry *new_tle = NULL;
 
-		if (tlist != NIL)
+		if (tlist_item != NULL)
 		{
-			TargetEntry *old_tle = (TargetEntry *) lfirst(tlist);
+			TargetEntry *old_tle = (TargetEntry *) lfirst(tlist_item);
 			Resdom	   *resdom = old_tle->resdom;
 
 			if (!resdom->resjunk && resdom->resno == attrno)
 			{
 				new_tle = old_tle;
-				tlist = lnext(tlist);
+				tlist_item = lnext(tlist_item);
 			}
 		}
 
@@ -259,9 +262,9 @@ expand_targetlist(List *tlist, int command_type,
 	 * an UPDATE in a table with dropped columns, or an inheritance child
 	 * table with extra columns.)
 	 */
-	while (tlist)
+	while (tlist_item)
 	{
-		TargetEntry *old_tle = (TargetEntry *) lfirst(tlist);
+		TargetEntry *old_tle = (TargetEntry *) lfirst(tlist_item);
 		Resdom	   *resdom = old_tle->resdom;
 
 		if (!resdom->resjunk)
@@ -275,7 +278,7 @@ expand_targetlist(List *tlist, int command_type,
 		}
 		new_tlist = lappend(new_tlist, old_tle);
 		attrno++;
-		tlist = lnext(tlist);
+		tlist_item = lnext(tlist_item);
 	}
 
 	heap_close(rel, AccessShareLock);
diff --git a/src/backend/optimizer/prep/prepunion.c b/src/backend/optimizer/prep/prepunion.c
index 25dfc2611e8..41809bd69e0 100644
--- a/src/backend/optimizer/prep/prepunion.c
+++ b/src/backend/optimizer/prep/prepunion.c
@@ -14,7 +14,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/optimizer/prep/prepunion.c,v 1.110 2004/05/11 22:43:55 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/optimizer/prep/prepunion.c,v 1.111 2004/05/26 04:41:26 neilc Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -420,15 +420,19 @@ generate_setop_tlist(List *colTypes, int flag,
 {
 	List	   *tlist = NIL;
 	int			resno = 1;
-	List	   *i;
+	ListCell   *i,
+			   *j,
+			   *k;
 	Resdom	   *resdom;
 	Node	   *expr;
 
+	j = list_head(input_tlist);
+	k = list_head(refnames_tlist);
 	foreach(i, colTypes)
 	{
 		Oid			colType = lfirsto(i);
-		TargetEntry *inputtle = (TargetEntry *) lfirst(input_tlist);
-		TargetEntry *reftle = (TargetEntry *) lfirst(refnames_tlist);
+		TargetEntry *inputtle = (TargetEntry *) lfirst(j);
+		TargetEntry *reftle = (TargetEntry *) lfirst(k);
 		int32		colTypmod;
 
 		Assert(inputtle->resdom->resno == resno);
@@ -476,8 +480,8 @@ generate_setop_tlist(List *colTypes, int flag,
 							pstrdup(reftle->resdom->resname),
 							false);
 		tlist = lappend(tlist, makeTargetEntry(resdom, (Expr *) expr));
-		input_tlist = lnext(input_tlist);
-		refnames_tlist = lnext(refnames_tlist);
+		j = lnext(j);
+		k = lnext(k);
 	}
 
 	if (flag >= 0)
@@ -518,11 +522,12 @@ generate_append_tlist(List *colTypes, bool flag,
 {
 	List	   *tlist = NIL;
 	int			resno = 1;
-	List	   *curColType;
+	ListCell   *curColType;
+	ListCell   *ref_tl_item;
 	int			colindex;
 	Resdom	   *resdom;
 	Node	   *expr;
-	List	   *planl;
+	ListCell   *planl;
 	int32	   *colTypmods;
 
 	/*
@@ -536,9 +541,9 @@ generate_append_tlist(List *colTypes, bool flag,
 	foreach(planl, input_plans)
 	{
 		Plan	   *subplan = (Plan *) lfirst(planl);
-		List	   *subtlist;
+		ListCell   *subtlist;
 
-		curColType = colTypes;
+		curColType = list_head(colTypes);
 		colindex = 0;
 		foreach(subtlist, subplan->targetlist)
 		{
@@ -546,11 +551,11 @@ generate_append_tlist(List *colTypes, bool flag,
 
 			if (subtle->resdom->resjunk)
 				continue;
-			Assert(curColType != NIL);
-			if (subtle->resdom->restype == lfirsto(curColType))
+			Assert(curColType != NULL);
+			if (subtle->resdom->restype == lfirst_oid(curColType))
 			{
 				/* If first subplan, copy the typmod; else compare */
-				if (planl == input_plans)
+				if (planl == list_head(input_plans))
 					colTypmods[colindex] = subtle->resdom->restypmod;
 				else if (subtle->resdom->restypmod != colTypmods[colindex])
 					colTypmods[colindex] = -1;
@@ -563,18 +568,18 @@ generate_append_tlist(List *colTypes, bool flag,
 			curColType = lnext(curColType);
 			colindex++;
 		}
-		Assert(curColType == NIL);
+		Assert(curColType == NULL);
 	}
 
 	/*
 	 * Now we can build the tlist for the Append.
 	 */
 	colindex = 0;
-	foreach(curColType, colTypes)
+	forboth(curColType, colTypes, ref_tl_item, refnames_tlist)
 	{
 		Oid			colType = lfirsto(curColType);
 		int32		colTypmod = colTypmods[colindex++];
-		TargetEntry *reftle = (TargetEntry *) lfirst(refnames_tlist);
+		TargetEntry *reftle = (TargetEntry *) lfirst(ref_tl_item);
 
 		Assert(reftle->resdom->resno == resno);
 		Assert(!reftle->resdom->resjunk);
@@ -589,7 +594,6 @@ generate_append_tlist(List *colTypes, bool flag,
 							pstrdup(reftle->resdom->resname),
 							false);
 		tlist = lappend(tlist, makeTargetEntry(resdom, (Expr *) expr));
-		refnames_tlist = lnext(refnames_tlist);
 	}
 
 	if (flag)
@@ -623,11 +627,12 @@ generate_append_tlist(List *colTypes, bool flag,
 static bool
 tlist_same_datatypes(List *tlist, List *colTypes, bool junkOK)
 {
-	List	   *i;
+	ListCell   *l;
+	ListCell   *curColType = list_head(colTypes);
 
-	foreach(i, tlist)
+	foreach(l, tlist)
 	{
-		TargetEntry *tle = (TargetEntry *) lfirst(i);
+		TargetEntry *tle = (TargetEntry *) lfirst(l);
 
 		if (tle->resdom->resjunk)
 		{
@@ -636,14 +641,14 @@ tlist_same_datatypes(List *tlist, List *colTypes, bool junkOK)
 		}
 		else
 		{
-			if (colTypes == NIL)
+			if (curColType == NULL)
 				return false;
-			if (tle->resdom->restype != lfirsto(colTypes))
+			if (tle->resdom->restype != lfirst_oid(curColType))
 				return false;
-			colTypes = lnext(colTypes);
+			curColType = lnext(curColType);
 		}
 	}
-	if (colTypes != NIL)
+	if (curColType != NULL)
 		return false;
 	return true;
 }
@@ -667,10 +672,10 @@ find_all_inheritors(Oid parentrel)
 	 */
 	while (unexamined_relids != NIL)
 	{
-		Oid			currentrel = lfirsto(unexamined_relids);
+		Oid			currentrel = linitial_oid(unexamined_relids);
 		List	   *currentchildren;
 
-		unexamined_relids = lnext(unexamined_relids);
+		unexamined_relids = list_delete_first(unexamined_relids);
 		examined_relids = lappendo(examined_relids, currentrel);
 		currentchildren = find_inheritance_children(currentrel);
 
@@ -719,7 +724,7 @@ expand_inherited_rtentry(Query *parse, Index rti, bool dup_parent)
 	Oid			parentOID;
 	List	   *inhOIDs;
 	List	   *inhRTIs;
-	List	   *l;
+	ListCell   *l;
 
 	/* Does RT entry allow inheritance? */
 	if (!rte->inh)
@@ -739,7 +744,7 @@ expand_inherited_rtentry(Query *parse, Index rti, bool dup_parent)
 	 * case.  This could happen despite above has_subclass() check, if
 	 * table once had a child but no longer does.
 	 */
-	if (lnext(inhOIDs) == NIL)
+	if (length(inhOIDs) < 2)
 		return NIL;
 	/* OK, it's an inheritance set; expand it */
 	if (dup_parent)
@@ -1020,7 +1025,7 @@ static List *
 adjust_inherited_tlist(List *tlist, Oid old_relid, Oid new_relid)
 {
 	bool		changed_it = false;
-	List	   *tl;
+	ListCell   *tl;
 	List	   *new_tlist;
 	bool		more;
 	int			attrno;