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, 34 insertions, 29 deletions

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;