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, 42 insertions, 49 deletions

diff --git a/src/backend/parser/parse_relation.c b/src/backend/parser/parse_relation.c
index de4bf093ee9..d7d50e187e3 100644
--- a/src/backend/parser/parse_relation.c
+++ b/src/backend/parser/parse_relation.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/parser/parse_relation.c,v 1.94 2004/04/18 18:12:58 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/parser/parse_relation.c,v 1.95 2004/05/26 04:41:30 neilc Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -140,7 +140,7 @@ scanNameSpaceForRefname(ParseState *pstate, Node *nsnode,
 		return NULL;
 	if (IsA(nsnode, RangeTblRef))
 	{
-		int			varno = ((RangeTblRef *) nsnode)->rtindex;
+		int			   varno = ((RangeTblRef *) nsnode)->rtindex;
 		RangeTblEntry *rte = rt_fetch(varno, pstate->p_rtable);
 
 		if (strcmp(rte->eref->aliasname, refname) == 0)
@@ -174,7 +174,7 @@ scanNameSpaceForRefname(ParseState *pstate, Node *nsnode,
 	}
 	else if (IsA(nsnode, List))
 	{
-		List	   *l;
+		ListCell   *l;
 
 		foreach(l, (List *) nsnode)
 		{
@@ -249,7 +249,7 @@ scanNameSpaceForRelid(ParseState *pstate, Node *nsnode, Oid relid)
 	}
 	else if (IsA(nsnode, List))
 	{
-		List	   *l;
+		ListCell   *l;
 
 		foreach(l, (List *) nsnode)
 		{
@@ -321,7 +321,7 @@ checkNameSpaceConflicts(ParseState *pstate, Node *namespace1,
 	}
 	else if (IsA(namespace1, List))
 	{
-		List	   *l;
+		ListCell   *l;
 
 		foreach(l, (List *) namespace1)
 			checkNameSpaceConflicts(pstate, lfirst(l), namespace2);
@@ -378,7 +378,7 @@ scanNameSpaceForConflict(ParseState *pstate, Node *nsnode,
 	}
 	else if (IsA(nsnode, List))
 	{
-		List	   *l;
+		ListCell   *l;
 
 		foreach(l, (List *) nsnode)
 			scanNameSpaceForConflict(pstate, lfirst(l), rte1, aliasname1);
@@ -397,7 +397,7 @@ int
 RTERangeTablePosn(ParseState *pstate, RangeTblEntry *rte, int *sublevels_up)
 {
 	int			index;
-	List	   *temp;
+	ListCell   *l;
 
 	if (sublevels_up)
 		*sublevels_up = 0;
@@ -405,9 +405,9 @@ RTERangeTablePosn(ParseState *pstate, RangeTblEntry *rte, int *sublevels_up)
 	while (pstate != NULL)
 	{
 		index = 1;
-		foreach(temp, pstate->p_rtable)
+		foreach(l, pstate->p_rtable)
 		{
-			if (rte == (RangeTblEntry *) lfirst(temp))
+			if (rte == (RangeTblEntry *) lfirst(l))
 				return index;
 			index++;
 		}
@@ -460,7 +460,7 @@ scanRTEForColumn(ParseState *pstate, RangeTblEntry *rte, char *colname)
 {
 	Node	   *result = NULL;
 	int			attnum = 0;
-	List	   *c;
+	ListCell   *c;
 
 	/*
 	 * Scan the user column names (or aliases) for a match. Complain if
@@ -546,7 +546,7 @@ colNameToVar(ParseState *pstate, char *colname, bool localonly)
 
 	while (pstate != NULL)
 	{
-		List	   *ns;
+		ListCell   *ns;
 
 		/*
 		 * We need to look only at top-level namespace items, and even for
@@ -841,7 +841,7 @@ addRangeTableEntryForSubquery(ParseState *pstate,
 	Alias	   *eref;
 	int			numaliases;
 	int			varattno;
-	List	   *tlistitem;
+	ListCell   *tlistitem;
 
 	rte->rtekind = RTE_SUBQUERY;
 	rte->relid = InvalidOid;
@@ -1027,7 +1027,7 @@ addRangeTableEntryForFunction(ParseState *pstate,
 	}
 	else if (functyptype == 'p' && funcrettype == RECORDOID)
 	{
-		List	   *col;
+		ListCell   *col;
 
 		/* Use the column definition list to form the alias list */
 		eref->colnames = NIL;
@@ -1101,11 +1101,8 @@ addRangeTableEntryForJoin(ParseState *pstate,
 
 	/* fill in any unspecified alias columns */
 	if (numaliases < length(colnames))
-	{
-		while (numaliases-- > 0)
-			colnames = lnext(colnames);
-		eref->colnames = nconc(eref->colnames, colnames);
-	}
+		eref->colnames = nconc(eref->colnames,
+							   list_copy_tail(colnames, numaliases));
 
 	rte->eref = eref;
 
@@ -1145,7 +1142,7 @@ isForUpdate(ParseState *pstate, char *refname)
 	{
 		if (pstate->p_forUpdate != NIL)
 		{
-			if (lfirst(pstate->p_forUpdate) == NULL)
+			if (linitial(pstate->p_forUpdate) == NULL)
 			{
 				/* all tables used in query */
 				return true;
@@ -1153,7 +1150,7 @@ isForUpdate(ParseState *pstate, char *refname)
 			else
 			{
 				/* just the named tables */
-				List	   *l;
+				ListCell   *l;
 
 				foreach(l, pstate->p_forUpdate)
 				{
@@ -1282,8 +1279,8 @@ expandRTE(ParseState *pstate, RangeTblEntry *rte,
 		case RTE_SUBQUERY:
 			{
 				/* Subquery RTE */
-				List	   *aliasp = rte->eref->colnames;
-				List	   *tlistitem;
+				ListCell	   *aliasp_item = list_head(rte->eref->colnames);
+				ListCell	   *tlistitem;
 
 				varattno = 0;
 				foreach(tlistitem, rte->subquery->targetList)
@@ -1298,10 +1295,10 @@ expandRTE(ParseState *pstate, RangeTblEntry *rte,
 					if (colnames)
 					{
 						/* Assume there is one alias per target item */
-						char	   *label = strVal(lfirst(aliasp));
+						char	   *label = strVal(lfirst(aliasp_item));
 
 						*colnames = lappend(*colnames, makeString(pstrdup(label)));
-						aliasp = lnext(aliasp);
+						aliasp_item = lnext(aliasp_item);
 					}
 
 					if (colvars)
@@ -1385,7 +1382,7 @@ expandRTE(ParseState *pstate, RangeTblEntry *rte,
 					 */
 					if (colnames)
 						*colnames = lappend(*colnames,
-											lfirst(rte->eref->colnames));
+											linitial(rte->eref->colnames));
 
 					if (colvars)
 					{
@@ -1400,7 +1397,7 @@ expandRTE(ParseState *pstate, RangeTblEntry *rte,
 				}
 				else if (functyptype == 'p' && funcrettype == RECORDOID)
 				{
-					List	   *col;
+					ListCell   *col;
 					int			attnum = 0;
 
 					foreach(col, coldeflist)
@@ -1442,39 +1439,36 @@ expandRTE(ParseState *pstate, RangeTblEntry *rte,
 		case RTE_JOIN:
 			{
 				/* Join RTE */
-				List	   *aliasp = rte->eref->colnames;
-				List	   *aliasvars = rte->joinaliasvars;
+				ListCell	*colname;
+				ListCell	*aliasvar;
+
+				Assert(length(rte->eref->colnames) == length(rte->joinaliasvars));
 
 				varattno = 0;
-				while (aliasp)
+				forboth (colname, rte->eref->colnames, aliasvar, rte->joinaliasvars)
 				{
-					Assert(aliasvars);
 					varattno++;
 
 					if (colnames)
 					{
-						char	   *label = strVal(lfirst(aliasp));
+						char	   *label = strVal(lfirst(colname));
 
 						*colnames = lappend(*colnames, makeString(pstrdup(label)));
 					}
 
 					if (colvars)
 					{
-						Node	   *aliasvar = (Node *) lfirst(aliasvars);
+						Node	   *avar = (Node *) lfirst(aliasvar);
 						Var		   *varnode;
 
 						varnode = makeVar(rtindex, varattno,
-										  exprType(aliasvar),
-										  exprTypmod(aliasvar),
+										  exprType(avar),
+										  exprTypmod(avar),
 										  sublevels_up);
 
 						*colvars = lappend(*colvars, varnode);
 					}
-
-					aliasp = lnext(aliasp);
-					aliasvars = lnext(aliasvars);
 				}
-				Assert(aliasvars == NIL);
 			}
 			break;
 		default:
@@ -1492,14 +1486,16 @@ expandRelAttrs(ParseState *pstate, RangeTblEntry *rte)
 {
 	List	   *names,
 			   *vars;
+	ListCell   *name,
+			   *var;
 	List	   *te_list = NIL;
 
 	expandRTE(pstate, rte, &names, &vars);
 
-	while (names)
+	forboth (name, names, var, vars)
 	{
-		char	   *label = strVal(lfirst(names));
-		Node	   *varnode = (Node *) lfirst(vars);
+		char	   *label = strVal(lfirst(name));
+		Node	   *varnode = (Node *) lfirst(var);
 		TargetEntry *te = makeNode(TargetEntry);
 
 		te->resdom = makeResdom((AttrNumber) pstate->p_next_resno++,
@@ -1509,12 +1505,9 @@ expandRelAttrs(ParseState *pstate, RangeTblEntry *rte)
 								false);
 		te->expr = (Expr *) varnode;
 		te_list = lappend(te_list, te);
-
-		names = lnext(names);
-		vars = lnext(vars);
 	}
 
-	Assert(vars == NIL);		/* lists not same length? */
+	Assert(name == NULL && var == NULL); /* lists not the same length? */
 
 	return te_list;
 }
@@ -1790,11 +1783,11 @@ get_rte_attribute_is_dropped(RangeTblEntry *rte, AttrNumber attnum)
 TargetEntry *
 get_tle_by_resno(List *tlist, AttrNumber resno)
 {
-	List	   *i;
+	ListCell  *l;
 
-	foreach(i, tlist)
+	foreach(l, tlist)
 	{
-		TargetEntry *tle = (TargetEntry *) lfirst(i);
+		TargetEntry *tle = (TargetEntry *) lfirst(l);
 
 		if (tle->resdom->resno == resno)
 			return tle;
@@ -1917,7 +1910,7 @@ static void
 warnAutoRange(ParseState *pstate, RangeVar *relation)
 {
 	bool		foundInFromCl = false;
-	List	   *temp;
+	ListCell   *temp;
 
 	if (!add_missing_from)
 	{