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, 40 insertions, 41 deletions

diff --git a/src/backend/parser/parse_clause.c b/src/backend/parser/parse_clause.c
index 2c6e9942899..610c4fa2960 100644
--- a/src/backend/parser/parse_clause.c
+++ b/src/backend/parser/parse_clause.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/parser/parse_clause.c,v 1.129 2004/05/23 17:10:54 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/parser/parse_clause.c,v 1.130 2004/05/26 04:41:29 neilc Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -79,7 +79,7 @@ static TargetEntry *findTargetlistEntry(ParseState *pstate, Node *node,
 void
 transformFromClause(ParseState *pstate, List *frmList)
 {
-	List	   *fl;
+	ListCell   *fl;
 
 	/*
 	 * The grammar will have produced a list of RangeVars,
@@ -231,14 +231,15 @@ extractRemainingColumns(List *common_colnames,
 {
 	List	   *new_colnames = NIL;
 	List	   *new_colvars = NIL;
-	List	   *lnames,
-			   *lvars = src_colvars;
+	ListCell   *lnames, *lvars;
 
-	foreach(lnames, src_colnames)
+	Assert(length(src_colnames) == length(src_colvars));
+
+	forboth(lnames, src_colnames, lvars, src_colvars)
 	{
 		char	   *colname = strVal(lfirst(lnames));
 		bool		match = false;
-		List	   *cnames;
+		ListCell   *cnames;
 
 		foreach(cnames, common_colnames)
 		{
@@ -256,8 +257,6 @@ extractRemainingColumns(List *common_colnames,
 			new_colnames = lappend(new_colnames, lfirst(lnames));
 			new_colvars = lappend(new_colvars, lfirst(lvars));
 		}
-
-		lvars = lnext(lvars);
 	}
 
 	*res_colnames = new_colnames;
@@ -273,8 +272,7 @@ static Node *
 transformJoinUsingClause(ParseState *pstate, List *leftVars, List *rightVars)
 {
 	Node	   *result = NULL;
-	List	   *lvars,
-			   *rvars = rightVars;
+	ListCell   *lvars, *rvars;
 
 	/*
 	 * We cheat a little bit here by building an untransformed operator
@@ -282,7 +280,7 @@ transformJoinUsingClause(ParseState *pstate, List *leftVars, List *rightVars)
 	 * because transformExpr() won't complain about already-transformed
 	 * subnodes.
 	 */
-	foreach(lvars, leftVars)
+	forboth(lvars, leftVars, rvars, rightVars)
 	{
 		Node	   *lvar = (Node *) lfirst(lvars);
 		Node	   *rvar = (Node *) lfirst(rvars);
@@ -299,8 +297,6 @@ transformJoinUsingClause(ParseState *pstate, List *leftVars, List *rightVars)
 			a = makeA_Expr(AEXPR_AND, NIL, result, (Node *) e);
 			result = (Node *) a;
 		}
-
-		rvars = lnext(rvars);
 	}
 
 	/*
@@ -314,7 +310,7 @@ transformJoinUsingClause(ParseState *pstate, List *leftVars, List *rightVars)
 	result = coerce_to_boolean(pstate, result, "JOIN/USING");
 
 	return result;
-}	/* transformJoinUsingClause() */
+}
 
 /* transformJoinOnClause()
  *	  Transform the qual conditions for JOIN/ON.
@@ -435,7 +431,7 @@ transformRangeSubselect(ParseState *pstate, RangeSubselect *r)
 	 */
 	if (length(parsetrees) != 1)
 		elog(ERROR, "unexpected parse analysis result for subquery in FROM");
-	query = (Query *) lfirst(parsetrees);
+	query = (Query *) linitial(parsetrees);
 	if (query == NULL || !IsA(query, Query))
 		elog(ERROR, "unexpected parse analysis result for subquery in FROM");
 
@@ -686,7 +682,7 @@ transformFromClauseItem(ParseState *pstate, Node *n, List **containedRels)
 		if (j->isNatural)
 		{
 			List	   *rlist = NIL;
-			List	   *lx,
+			ListCell   *lx,
 					   *rx;
 
 			Assert(j->using == NIL);	/* shouldn't have USING() too */
@@ -731,14 +727,14 @@ transformFromClauseItem(ParseState *pstate, Node *n, List **containedRels)
 			List	   *ucols = j->using;
 			List	   *l_usingvars = NIL;
 			List	   *r_usingvars = NIL;
-			List	   *ucol;
+			ListCell   *ucol;
 
 			Assert(j->quals == NULL);	/* shouldn't have ON() too */
 
 			foreach(ucol, ucols)
 			{
 				char	   *u_colname = strVal(lfirst(ucol));
-				List	   *col;
+				ListCell   *col;
 				int			ndx;
 				int			l_index = -1;
 				int			r_index = -1;
@@ -1083,7 +1079,7 @@ static TargetEntry *
 findTargetlistEntry(ParseState *pstate, Node *node, List **tlist, int clause)
 {
 	TargetEntry *target_result = NULL;
-	List	   *tl;
+	ListCell   *tl;
 	Node	   *expr;
 
 	/*----------
@@ -1129,7 +1125,7 @@ findTargetlistEntry(ParseState *pstate, Node *node, List **tlist, int clause)
 		length(((ColumnRef *) node)->fields) == 1 &&
 		((ColumnRef *) node)->indirection == NIL)
 	{
-		char	   *name = strVal(lfirst(((ColumnRef *) node)->fields));
+		char	   *name = strVal(linitial(((ColumnRef *) node)->fields));
 
 		if (clause == GROUP_CLAUSE)
 		{
@@ -1255,8 +1251,11 @@ List *
 transformGroupClause(ParseState *pstate, List *grouplist,
 					 List **targetlist, List *sortClause)
 {
-	List	   *glist = NIL,
-			   *gl;
+	List	   *glist = NIL;
+	ListCell   *gl;
+	ListCell   *sortItem;
+
+	sortItem = list_head(sortClause);
 
 	foreach(gl, grouplist)
 	{
@@ -1293,17 +1292,17 @@ transformGroupClause(ParseState *pstate, List *grouplist,
 		 * any user-supplied ordering operator will bring equal values
 		 * together, which is all that GROUP BY needs.
 		 */
-		if (sortClause &&
-			((SortClause *) lfirst(sortClause))->tleSortGroupRef ==
+		if (sortItem &&
+			((SortClause *) lfirst(sortItem))->tleSortGroupRef ==
 			tle->resdom->ressortgroupref)
 		{
-			ordering_op = ((SortClause *) lfirst(sortClause))->sortop;
-			sortClause = lnext(sortClause);
+			ordering_op = ((SortClause *) lfirst(sortItem))->sortop;
+			sortItem = lnext(sortItem);
 		}
 		else
 		{
 			ordering_op = ordering_oper_opid(restype);
-			sortClause = NIL;	/* disregard ORDER BY once match fails */
+			sortItem = NULL;	/* disregard ORDER BY once match fails */
 		}
 
 		grpcl = makeNode(GroupClause);
@@ -1329,7 +1328,7 @@ transformSortClause(ParseState *pstate,
 					bool resolveUnknown)
 {
 	List	   *sortlist = NIL;
-	List	   *olitem;
+	ListCell   *olitem;
 
 	foreach(olitem, orderlist)
 	{
@@ -1361,14 +1360,14 @@ transformDistinctClause(ParseState *pstate, List *distinctlist,
 						List **targetlist, List **sortClause)
 {
 	List	   *result = NIL;
-	List	   *slitem;
-	List	   *dlitem;
+	ListCell   *slitem;
+	ListCell   *dlitem;
 
 	/* No work if there was no DISTINCT clause */
 	if (distinctlist == NIL)
 		return NIL;
 
-	if (lfirst(distinctlist) == NIL)
+	if (linitial(distinctlist) == NULL)
 	{
 		/* We had SELECT DISTINCT */
 
@@ -1423,7 +1422,7 @@ transformDistinctClause(ParseState *pstate, List *distinctlist,
 		 * match in any order, but implementing that check seems like more
 		 * trouble than it's worth.
 		 */
-		List	   *nextsortlist = *sortClause;
+		ListCell   *nextsortlist = list_head(*sortClause);
 
 		foreach(dlitem, distinctlist)
 		{
@@ -1432,7 +1431,7 @@ transformDistinctClause(ParseState *pstate, List *distinctlist,
 			tle = findTargetlistEntry(pstate, lfirst(dlitem),
 									  targetlist, DISTINCT_ON_CLAUSE);
 
-			if (nextsortlist != NIL)
+			if (nextsortlist != NULL)
 			{
 				SortClause *scl = (SortClause *) lfirst(nextsortlist);
 
@@ -1463,7 +1462,7 @@ transformDistinctClause(ParseState *pstate, List *distinctlist,
 						break;
 					}
 				}
-				if (slitem == NIL)		/* should not happen */
+				if (slitem == NULL)		/* should not happen */
 					elog(ERROR, "failed to add DISTINCT ON clause to target list");
 			}
 		}
@@ -1486,11 +1485,11 @@ List *
 addAllTargetsToSortList(ParseState *pstate, List *sortlist,
 						List *targetlist, bool resolveUnknown)
 {
-	List	   *i;
+	ListCell  *l;
 
-	foreach(i, targetlist)
+	foreach(l, targetlist)
 	{
-		TargetEntry *tle = (TargetEntry *) lfirst(i);
+		TargetEntry *tle = (TargetEntry *) lfirst(l);
 
 		if (!tle->resdom->resjunk)
 			sortlist = addTargetToSortList(pstate, tle,
@@ -1575,7 +1574,7 @@ Index
 assignSortGroupRef(TargetEntry *tle, List *tlist)
 {
 	Index		maxRef;
-	List	   *l;
+	ListCell   *l;
 
 	if (tle->resdom->ressortgroupref)	/* already has one? */
 		return tle->resdom->ressortgroupref;
@@ -1605,15 +1604,15 @@ bool
 targetIsInSortList(TargetEntry *tle, List *sortList)
 {
 	Index		ref = tle->resdom->ressortgroupref;
-	List	   *i;
+	ListCell   *l;
 
 	/* no need to scan list if tle has no marker */
 	if (ref == 0)
 		return false;
 
-	foreach(i, sortList)
+	foreach(l, sortList)
 	{
-		SortClause *scl = (SortClause *) lfirst(i);
+		SortClause *scl = (SortClause *) lfirst(l);
 
 		if (scl->tleSortGroupRef == ref)
 			return true;