Code cleanup inspired by recent resname bug report (doesn't fix the bug

yet, though).  Avoid using nth() to fetch tlist entries; provide a
common routine get_tle_by_resno() to search a tlist for a particular
resno.  This replaces a couple uses of nth() and a dozen hand-coded
search loops.  Also, replace a few uses of nth(length-1, list) with
llast().

2 files changed, 15 insertions, 24 deletions

diff --git a/src/backend/commands/comment.c b/src/backend/commands/comment.c
index 4ed3614506..df09337d72 100644
--- a/src/backend/commands/comment.c
+++ b/src/backend/commands/comment.c
@@ -7,7 +7,7 @@
  * Copyright (c) 1996-2003, PostgreSQL Global Development Group
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/commands/comment.c,v 1.69 2003/08/04 23:59:37 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/commands/comment.c,v 1.70 2003/08/11 20:46:46 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -365,7 +365,7 @@ CommentAttribute(List *qualname, char *comment)
 	if (nnames < 2)				/* parser messed up */
 		elog(ERROR, "must specify relation and attribute");
 	relname = ltruncate(nnames - 1, listCopy(qualname));
-	attrname = strVal(nth(nnames - 1, qualname));
+	attrname = strVal(llast(qualname));
 
 	/* Open the containing relation to ensure it won't go away meanwhile */
 	rel = makeRangeVarFromNameList(relname);
@@ -583,7 +583,7 @@ CommentRule(List *qualname, char *comment)
 		/* New-style: rule and relname both provided */
 		Assert(nnames >= 2);
 		relname = ltruncate(nnames - 1, listCopy(qualname));
-		rulename = strVal(nth(nnames - 1, qualname));
+		rulename = strVal(llast(qualname));
 
 		/* Open the owning relation to ensure it won't go away meanwhile */
 		rel = makeRangeVarFromNameList(relname);
@@ -778,7 +778,7 @@ CommentTrigger(List *qualname, char *comment)
 	if (nnames < 2)				/* parser messed up */
 		elog(ERROR, "must specify relation and trigger");
 	relname = ltruncate(nnames - 1, listCopy(qualname));
-	trigname = strVal(nth(nnames - 1, qualname));
+	trigname = strVal(llast(qualname));
 
 	/* Open the owning relation to ensure it won't go away meanwhile */
 	rel = makeRangeVarFromNameList(relname);
@@ -856,7 +856,7 @@ CommentConstraint(List *qualname, char *comment)
 	if (nnames < 2)				/* parser messed up */
 		elog(ERROR, "must specify relation and constraint");
 	relName = ltruncate(nnames - 1, listCopy(qualname));
-	conName = strVal(nth(nnames - 1, qualname));
+	conName = strVal(llast(qualname));
 
 	/* Open the owning relation to ensure it won't go away meanwhile */
 	rel = makeRangeVarFromNameList(relName);
diff --git a/src/backend/commands/explain.c b/src/backend/commands/explain.c
index 6e2b857271..e664b3e494 100644
--- a/src/backend/commands/explain.c
+++ b/src/backend/commands/explain.c
@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1994-5, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/commands/explain.c,v 1.114 2003/08/08 21:41:30 momjian Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/commands/explain.c,v 1.115 2003/08/11 20:46:46 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -947,7 +947,6 @@ show_sort_keys(List *tlist, int nkeys, AttrNumber *keycols,
 	List	   *context;
 	bool		useprefix;
 	int			keyno;
-	List	   *tl;
 	char	   *exprstr;
 	Relids		varnos;
 	int			i;
@@ -993,25 +992,17 @@ show_sort_keys(List *tlist, int nkeys, AttrNumber *keycols,
 	{
 		/* find key expression in tlist */
 		AttrNumber	keyresno = keycols[keyno];
+		TargetEntry *target = get_tle_by_resno(tlist, keyresno);
 
-		foreach(tl, tlist)
-		{
-			TargetEntry *target = (TargetEntry *) lfirst(tl);
-
-			if (target->resdom->resno == keyresno)
-			{
-				/* Deparse the expression, showing any top-level cast */
-				exprstr = deparse_expression((Node *) target->expr, context,
-											 useprefix, true);
-				/* And add to str */
-				if (keyno > 0)
-					appendStringInfo(str, ", ");
-				appendStringInfo(str, "%s", exprstr);
-				break;
-			}
-		}
-		if (tl == NIL)
+		if (!target)
 			elog(ERROR, "no tlist entry for key %d", keyresno);
+		/* Deparse the expression, showing any top-level cast */
+		exprstr = deparse_expression((Node *) target->expr, context,
+									 useprefix, true);
+		/* And add to str */
+		if (keyno > 0)
+			appendStringInfo(str, ", ");
+		appendStringInfo(str, "%s", exprstr);
 	}
 
 	appendStringInfo(str, "\n");