From 302f1a86dc1125f681b9a3b3509d1be7e33b0e4f Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Mon, 11 Aug 2003 23:04:50 +0000
Subject: [PATCH] Rewriter and planner should use only resno, not resname, to
 identify target columns in INSERT and UPDATE targetlists.  Don't rely on
 resname to be accurate in ruleutils, either.  This fixes bug reported by
 Donald Fraser, in which renaming a column referenced in a rule did not work
 very well.

---
 src/backend/access/common/tupdesc.c    | 16 +++---
 src/backend/catalog/dependency.c       |  6 +--
 src/backend/nodes/print.c              |  5 +-
 src/backend/optimizer/prep/preptlist.c |  4 +-
 src/backend/optimizer/prep/prepunion.c | 21 +++++---
 src/backend/parser/analyze.c           | 13 +++--
 src/backend/parser/parse_relation.c    | 12 +----
 src/backend/parser/parse_target.c      | 17 ++++---
 src/backend/rewrite/rewriteHandler.c   | 22 ++++-----
 src/backend/utils/adt/ruleutils.c      | 68 +++++++++++---------------
 src/backend/utils/cache/lsyscache.c    | 25 ++++++++--
 src/backend/utils/misc/guc.c           |  6 +--
 src/include/access/tupdesc.h           |  4 +-
 src/include/nodes/primnodes.h          | 39 +++++++++++----
 src/include/utils/lsyscache.h          |  3 +-
 15 files changed, 145 insertions(+), 116 deletions(-)

diff --git a/src/backend/access/common/tupdesc.c b/src/backend/access/common/tupdesc.c
index b76e03ed43..9a40c08ca9 100644
--- a/src/backend/access/common/tupdesc.c
+++ b/src/backend/access/common/tupdesc.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/access/common/tupdesc.c,v 1.98 2003/08/04 02:39:56 momjian Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/access/common/tupdesc.c,v 1.99 2003/08/11 23:04:49 tgl Exp $
  *
  * NOTES
  *	  some of the executor utility code such as "ExecTypeFromTL" should be
@@ -357,7 +357,7 @@ equalTupleDescs(TupleDesc tupdesc1, TupleDesc tupdesc2)
 void
 TupleDescInitEntry(TupleDesc desc,
 				   AttrNumber attributeNumber,
-				   char *attributeName,
+				   const char *attributeName,
 				   Oid oidtypeid,
 				   int32 typmod,
 				   int attdim,
@@ -373,13 +373,6 @@ TupleDescInitEntry(TupleDesc desc,
 	AssertArg(PointerIsValid(desc));
 	AssertArg(attributeNumber >= 1);
 	AssertArg(attributeNumber <= desc->natts);
-
-	/*
-	 * attributeName's are sometimes NULL, from resdom's.  I don't know
-	 * why that is, though -- Jolly
-	 */
-/*	  AssertArg(NameIsValid(attributeName));*/
-
 	AssertArg(!PointerIsValid(desc->attrs[attributeNumber - 1]));
 
 	/*
@@ -394,6 +387,11 @@ TupleDescInitEntry(TupleDesc desc,
 	 */
 	att->attrelid = 0;			/* dummy value */
 
+	/*
+	 * Note: attributeName can be NULL, because the planner doesn't always
+	 * fill in valid resname values in targetlists, particularly for resjunk
+	 * attributes.
+	 */
 	if (attributeName != NULL)
 		namestrcpy(&(att->attname), attributeName);
 	else
diff --git a/src/backend/catalog/dependency.c b/src/backend/catalog/dependency.c
index 870a2320c2..8155f4fff3 100644
--- a/src/backend/catalog/dependency.c
+++ b/src/backend/catalog/dependency.c
@@ -8,7 +8,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/catalog/dependency.c,v 1.30 2003/08/04 02:39:58 momjian Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/catalog/dependency.c,v 1.31 2003/08/11 23:04:49 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -1439,8 +1439,8 @@ getObjectDescription(const ObjectAddress *object)
 			getRelationDescription(&buffer, object->objectId);
 			if (object->objectSubId != 0)
 				appendStringInfo(&buffer, " column %s",
-								 get_attname(object->objectId,
-											 object->objectSubId));
+								 get_relid_attribute_name(object->objectId,
+														  object->objectSubId));
 			break;
 
 		case OCLASS_PROC:
diff --git a/src/backend/nodes/print.c b/src/backend/nodes/print.c
index c3d702316d..c3417d8efa 100644
--- a/src/backend/nodes/print.c
+++ b/src/backend/nodes/print.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/nodes/print.c,v 1.63 2003/08/04 02:39:59 momjian Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/nodes/print.c,v 1.64 2003/08/11 23:04:49 tgl Exp $
  *
  * HISTORY
  *	  AUTHOR			DATE			MAJOR EVENT
@@ -448,7 +448,8 @@ print_tl(List *tlist, List *rtable)
 	{
 		TargetEntry *tle = lfirst(tl);
 
-		printf("\t%d %s\t", tle->resdom->resno, tle->resdom->resname);
+		printf("\t%d %s\t", tle->resdom->resno,
+			   tle->resdom->resname ? tle->resdom->resname : "<null>");
 		if (tle->resdom->ressortgroupref != 0)
 			printf("(%u):\t", tle->resdom->ressortgroupref);
 		else
diff --git a/src/backend/optimizer/prep/preptlist.c b/src/backend/optimizer/prep/preptlist.c
index 5796870e76..f2368d0677 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
- *	  $Header: /cvsroot/pgsql/src/backend/optimizer/prep/preptlist.c,v 1.64 2003/08/04 02:40:01 momjian Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/optimizer/prep/preptlist.c,v 1.65 2003/08/11 23:04:49 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -150,8 +150,6 @@ expand_targetlist(List *tlist, int command_type,
 
 			if (!resdom->resjunk && resdom->resno == attrno)
 			{
-				Assert(strcmp(resdom->resname,
-							  NameStr(att_tup->attname)) == 0);
 				new_tle = old_tle;
 				tlist = lnext(tlist);
 			}
diff --git a/src/backend/optimizer/prep/prepunion.c b/src/backend/optimizer/prep/prepunion.c
index d023fd97a8..281b15571d 100644
--- a/src/backend/optimizer/prep/prepunion.c
+++ b/src/backend/optimizer/prep/prepunion.c
@@ -14,7 +14,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/optimizer/prep/prepunion.c,v 1.103 2003/08/04 02:40:01 momjian Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/optimizer/prep/prepunion.c,v 1.104 2003/08/11 23:04:49 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -64,7 +64,7 @@ static bool tlist_same_datatypes(List *tlist, List *colTypes, bool junkOK);
 static Node *adjust_inherited_attrs_mutator(Node *node,
 							   adjust_inherited_attrs_context *context);
 static Relids adjust_relid_set(Relids relids, Index oldrelid, Index newrelid);
-static List *adjust_inherited_tlist(List *tlist, Oid new_relid);
+static List *adjust_inherited_tlist(List *tlist, Oid old_relid, Oid new_relid);
 
 
 /*
@@ -787,6 +787,7 @@ adjust_inherited_attrs(Node *node,
 			if (newnode->commandType == CMD_UPDATE)
 				newnode->targetList =
 					adjust_inherited_tlist(newnode->targetList,
+										   old_relid,
 										   new_relid);
 		}
 		return (Node *) newnode;
@@ -812,9 +813,10 @@ adjust_inherited_attrs_mutator(Node *node,
 			var->varnoold = context->new_rt_index;
 			if (var->varattno > 0)
 			{
-				char	   *attname = get_attname(context->old_relid,
-												  var->varattno);
+				char	   *attname;
 
+				attname = get_relid_attribute_name(context->old_relid,
+												   var->varattno);
 				var->varattno = get_attnum(context->new_relid, attname);
 				if (var->varattno == InvalidAttrNumber)
 					elog(ERROR, "attribute \"%s\" of relation \"%s\" does not exist",
@@ -976,7 +978,7 @@ adjust_relid_set(Relids relids, Index oldrelid, Index newrelid)
  * Note that this is not needed for INSERT because INSERT isn't inheritable.
  */
 static List *
-adjust_inherited_tlist(List *tlist, Oid new_relid)
+adjust_inherited_tlist(List *tlist, Oid old_relid, Oid new_relid)
 {
 	bool		changed_it = false;
 	List	   *tl;
@@ -989,21 +991,26 @@ adjust_inherited_tlist(List *tlist, Oid new_relid)
 	{
 		TargetEntry *tle = (TargetEntry *) lfirst(tl);
 		Resdom	   *resdom = tle->resdom;
+		char	   *attname;
 
 		if (resdom->resjunk)
 			continue;			/* ignore junk items */
 
-		attrno = get_attnum(new_relid, resdom->resname);
+		attname = get_relid_attribute_name(old_relid, resdom->resno);
+		attrno = get_attnum(new_relid, attname);
 		if (attrno == InvalidAttrNumber)
 			elog(ERROR, "attribute \"%s\" of relation \"%s\" does not exist",
-				 resdom->resname, get_rel_name(new_relid));
+				 attname, get_rel_name(new_relid));
 		if (resdom->resno != attrno)
 		{
 			resdom = (Resdom *) copyObject((Node *) resdom);
 			resdom->resno = attrno;
+			resdom->resname = attname;
 			tle->resdom = resdom;
 			changed_it = true;
 		}
+		else
+			pfree(attname);
 	}
 
 	/*
diff --git a/src/backend/parser/analyze.c b/src/backend/parser/analyze.c
index ea9a1d80a8..832c98a1c1 100644
--- a/src/backend/parser/analyze.c
+++ b/src/backend/parser/analyze.c
@@ -6,7 +6,7 @@
  * Portions Copyright (c) 1996-2003, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- *	$Header: /cvsroot/pgsql/src/backend/parser/analyze.c,v 1.286 2003/08/08 21:41:55 momjian Exp $
+ *	$Header: /cvsroot/pgsql/src/backend/parser/analyze.c,v 1.287 2003/08/11 23:04:49 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -2124,10 +2124,12 @@ transformSetOperationStmt(ParseState *pstate, SelectStmt *stmt)
 	{
 		Oid			colType = lfirsto(dtlist);
 		Resdom	   *leftResdom = ((TargetEntry *) lfirst(lefttl))->resdom;
-		char	   *colName = pstrdup(leftResdom->resname);
+		char	   *colName;
 		Resdom	   *resdom;
 		Expr	   *expr;
 
+		Assert(!leftResdom->resjunk);
+		colName = pstrdup(leftResdom->resname);
 		resdom = makeResdom((AttrNumber) pstate->p_next_resno++,
 							colType,
 							-1,
@@ -2501,11 +2503,12 @@ transformUpdateStmt(ParseState *pstate, UpdateStmt *stmt)
 		{
 			/*
 			 * Resjunk nodes need no additional processing, but be sure
-			 * they have names and resnos that do not match any target
-			 * columns; else rewriter or planner might get confused.
+			 * they have resnos that do not match any target columns;
+			 * else rewriter or planner might get confused.  They don't
+			 * need a resname either.
 			 */
-			resnode->resname = "?resjunk?";
 			resnode->resno = (AttrNumber) pstate->p_next_resno++;
+			resnode->resname = NULL;
 			continue;
 		}
 		if (origTargetList == NIL)
diff --git a/src/backend/parser/parse_relation.c b/src/backend/parser/parse_relation.c
index b8c2d8c8e3..ba1eea0475 100644
--- a/src/backend/parser/parse_relation.c
+++ b/src/backend/parser/parse_relation.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/parser/parse_relation.c,v 1.88 2003/08/11 20:46:46 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/parser/parse_relation.c,v 1.89 2003/08/11 23:04:49 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -1516,8 +1516,6 @@ expandRelAttrs(ParseState *pstate, RangeTblEntry *rte)
 char *
 get_rte_attribute_name(RangeTblEntry *rte, AttrNumber attnum)
 {
-	char	   *attname;
-
 	if (attnum == InvalidAttrNumber)
 		return "*";
 
@@ -1535,13 +1533,7 @@ get_rte_attribute_name(RangeTblEntry *rte, AttrNumber attnum)
 	 * built (which can easily happen for rules).
 	 */
 	if (rte->rtekind == RTE_RELATION)
-	{
-		attname = get_attname(rte->relid, attnum);
-		if (attname == NULL)
-			elog(ERROR, "cache lookup failed for attribute %d of relation %u",
-				 attnum, rte->relid);
-		return attname;
-	}
+		return get_relid_attribute_name(rte->relid, attnum);
 
 	/*
 	 * Otherwise use the column name from eref.  There should always be
diff --git a/src/backend/parser/parse_target.c b/src/backend/parser/parse_target.c
index a525e8795f..5d5ee56eb1 100644
--- a/src/backend/parser/parse_target.c
+++ b/src/backend/parser/parse_target.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/parser/parse_target.c,v 1.111 2003/08/11 20:46:46 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/parser/parse_target.c,v 1.112 2003/08/11 23:04:49 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -71,7 +71,7 @@ transformTargetEntry(ParseState *pstate,
 	type_id = exprType(expr);
 	type_mod = exprTypmod(expr);
 
-	if (colname == NULL)
+	if (colname == NULL && !resjunk)
 	{
 		/*
 		 * Generate a suitable column name for a column without any
@@ -428,14 +428,19 @@ updateTargetListEntry(ParseState *pstate,
 
 	/*
 	 * The result of the target expression should now match the
-	 * destination column's type.  Also, reset the resname and resno to
-	 * identify the destination column --- rewriter and planner depend on
-	 * that!
+	 * destination column's type.
 	 */
 	resnode->restype = attrtype;
 	resnode->restypmod = attrtypmod;
-	resnode->resname = colname;
+	/*
+	 * Set the resno to identify the target column --- the rewriter and
+	 * planner depend on this.  We also set the resname to identify the
+	 * target column, but this is only for debugging purposes; it should
+	 * not be relied on.  (In particular, it might be out of date in a
+	 * stored rule.)
+	 */
 	resnode->resno = (AttrNumber) attrno;
+	resnode->resname = colname;
 }
 
 
diff --git a/src/backend/rewrite/rewriteHandler.c b/src/backend/rewrite/rewriteHandler.c
index e8f3c185d1..d0ca89ee6a 100644
--- a/src/backend/rewrite/rewriteHandler.c
+++ b/src/backend/rewrite/rewriteHandler.c
@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/rewrite/rewriteHandler.c,v 1.128 2003/08/08 21:41:56 momjian Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/rewrite/rewriteHandler.c,v 1.129 2003/08/11 23:04:49 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -48,7 +48,8 @@ static Query *rewriteRuleAction(Query *parsetree,
 static List *adjustJoinTreeList(Query *parsetree, bool removert, int rt_index);
 static void rewriteTargetList(Query *parsetree, Relation target_relation);
 static TargetEntry *process_matched_tle(TargetEntry *src_tle,
-					TargetEntry *prior_tle);
+										TargetEntry *prior_tle,
+										const char *attrName);
 static void markQueryForUpdate(Query *qry, bool skipOldNew);
 static List *matchLocks(CmdType event, RuleLock *rulelocks,
 		   int varno, Query *parsetree);
@@ -312,8 +313,7 @@ rewriteTargetList(Query *parsetree, Relation target_relation)
 			continue;
 
 		/*
-		 * Look for targetlist entries matching this attr.	We match by
-		 * resno, but the resname should match too.
+		 * Look for targetlist entries matching this attr.
 		 *
 		 * Junk attributes are not candidates to be matched.
 		 */
@@ -324,9 +324,8 @@ rewriteTargetList(Query *parsetree, Relation target_relation)
 
 			if (!resdom->resjunk && resdom->resno == attrno)
 			{
-				Assert(strcmp(resdom->resname,
-							  NameStr(att_tup->attname)) == 0);
-				new_tle = process_matched_tle(old_tle, new_tle);
+				new_tle = process_matched_tle(old_tle, new_tle,
+											  NameStr(att_tup->attname));
 				/* keep scanning to detect multiple assignments to attr */
 			}
 		}
@@ -424,11 +423,12 @@ rewriteTargetList(Query *parsetree, Relation target_relation)
  * Convert a matched TLE from the original tlist into a correct new TLE.
  *
  * This routine detects and handles multiple assignments to the same target
- * attribute.
+ * attribute.  (The attribute name is needed only for error messages.)
  */
 static TargetEntry *
 process_matched_tle(TargetEntry *src_tle,
-					TargetEntry *prior_tle)
+					TargetEntry *prior_tle,
+					const char *attrName)
 {
 	Resdom	   *resdom = src_tle->resdom;
 	Node	   *priorbottom;
@@ -456,7 +456,7 @@ process_matched_tle(TargetEntry *src_tle,
 		ereport(ERROR,
 				(errcode(ERRCODE_SYNTAX_ERROR),
 				 errmsg("multiple assignments to same attribute \"%s\"",
-						resdom->resname)));
+						attrName)));
 
 	/*
 	 * Prior TLE could be a nest of ArrayRefs if we do this more than
@@ -470,7 +470,7 @@ process_matched_tle(TargetEntry *src_tle,
 		ereport(ERROR,
 				(errcode(ERRCODE_SYNTAX_ERROR),
 				 errmsg("multiple assignments to same attribute \"%s\"",
-						resdom->resname)));
+						attrName)));
 
 	/*
 	 * Looks OK to nest 'em.
diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index 49cc73f24e..83989292d6 100644
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -3,7 +3,7 @@
  *				back to source text
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/utils/adt/ruleutils.c,v 1.150 2003/08/08 21:42:09 momjian Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/utils/adt/ruleutils.c,v 1.151 2003/08/11 23:04:49 tgl Exp $
  *
  *	  This software is copyrighted by Jan Wieck - Hamburg.
  *
@@ -207,7 +207,6 @@ static char *generate_relation_name(Oid relid);
 static char *generate_function_name(Oid funcid, int nargs, Oid *argtypes);
 static char *generate_operator_name(Oid operid, Oid arg1, Oid arg2);
 static void print_operator_name(StringInfo buf, List *opname);
-static char *get_relid_attribute_name(Oid relid, AttrNumber attnum);
 
 #define only_marker(rte)  ((rte)->inh ? "" : "ONLY ")
 
@@ -1140,7 +1139,7 @@ decompile_column_index_array(Datum column_index_array, Oid relId,
 	{
 		char	   *colName;
 
-		colName = get_attname(relId, DatumGetInt16(keys[j]));
+		colName = get_relid_attribute_name(relId, DatumGetInt16(keys[j]));
 
 		if (j == 0)
 			appendStringInfo(buf, "%s",
@@ -1901,7 +1900,6 @@ get_basic_select_query(Query *query, deparse_context *context,
 	foreach(l, query->targetList)
 	{
 		TargetEntry *tle = (TargetEntry *) lfirst(l);
-		bool		tell_as = false;
 		char	   *colname;
 
 		if (tle->resdom->resjunk)
@@ -1924,24 +1922,30 @@ get_basic_select_query(Query *query, deparse_context *context,
 		else
 			colname = tle->resdom->resname;
 
-		/* Check if we must say AS ... */
-		if (!IsA(tle->expr, Var))
-			tell_as = (strcmp(colname, "?column?") != 0);
-		else
+		if (colname)			/* resname could be NULL */
 		{
-			Var		   *var = (Var *) (tle->expr);
-			char	   *schemaname;
-			char	   *refname;
-			char	   *attname;
+			/* Check if we must say AS ... */
+			bool		tell_as;
 
-			get_names_for_var(var, context, &schemaname, &refname, &attname);
-			tell_as = (attname == NULL ||
-					   strcmp(attname, colname) != 0);
-		}
+			if (!IsA(tle->expr, Var))
+				tell_as = (strcmp(colname, "?column?") != 0);
+			else
+			{
+				Var		   *var = (Var *) (tle->expr);
+				char	   *schemaname;
+				char	   *refname;
+				char	   *attname;
 
-		/* and do if so */
-		if (tell_as)
-			appendStringInfo(buf, " AS %s", quote_identifier(colname));
+				get_names_for_var(var, context,
+								  &schemaname, &refname, &attname);
+				tell_as = (attname == NULL ||
+						   strcmp(attname, colname) != 0);
+			}
+
+			/* and do if so */
+			if (tell_as)
+				appendStringInfo(buf, " AS %s", quote_identifier(colname));
+		}
 	}
 
 	/* Add the FROM clause if needed */
@@ -2151,7 +2155,9 @@ get_insert_query_def(Query *query, deparse_context *context)
 
 		appendStringInfo(buf, sep);
 		sep = ", ";
-		appendStringInfo(buf, "%s", quote_identifier(tle->resdom->resname));
+		appendStringInfo(buf, "%s",
+						 quote_identifier(get_relid_attribute_name(rte->relid,
+														tle->resdom->resno)));
 	}
 	appendStringInfo(buf, ") ");
 
@@ -2225,7 +2231,8 @@ get_update_query_def(Query *query, deparse_context *context)
 		 */
 		if (!tleIsArrayAssign(tle))
 			appendStringInfo(buf, "%s = ",
-							 quote_identifier(tle->resdom->resname));
+						quote_identifier(get_relid_attribute_name(rte->relid,
+														tle->resdom->resno)));
 		get_rule_expr((Node *) tle->expr, context, false);
 	}
 
@@ -4351,22 +4358,3 @@ print_operator_name(StringInfo buf, List *opname)
 		appendStringInfo(buf, "%s)", strVal(lfirst(opname)));
 	}
 }
-
-/*
- * get_relid_attribute_name
- *		Get an attribute name by its relations Oid and its attnum
- *
- * Same as underlying syscache routine get_attname(), except that error
- * is handled by elog() instead of returning NULL.
- */
-static char *
-get_relid_attribute_name(Oid relid, AttrNumber attnum)
-{
-	char	   *attname;
-
-	attname = get_attname(relid, attnum);
-	if (attname == NULL)
-		elog(ERROR, "cache lookup failed for attribute %d of relation %u",
-			 attnum, relid);
-	return attname;
-}
diff --git a/src/backend/utils/cache/lsyscache.c b/src/backend/utils/cache/lsyscache.c
index 0dfa0eb7c7..0faa097f34 100644
--- a/src/backend/utils/cache/lsyscache.c
+++ b/src/backend/utils/cache/lsyscache.c
@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/utils/cache/lsyscache.c,v 1.105 2003/08/04 02:40:06 momjian Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/utils/cache/lsyscache.c,v 1.106 2003/08/11 23:04:49 tgl Exp $
  *
  * NOTES
  *	  Eventually, the index information should go through here, too.
@@ -180,11 +180,10 @@ get_op_hash_function(Oid opno)
 
 /*
  * get_attname
- *
  *		Given the relation id and the attribute number,
  *		return the "attname" field from the attribute relation.
  *
- * Note: returns a palloc'd copy of the string, or NULL if no such operator.
+ * Note: returns a palloc'd copy of the string, or NULL if no such attribute.
  */
 char *
 get_attname(Oid relid, AttrNumber attnum)
@@ -208,6 +207,24 @@ get_attname(Oid relid, AttrNumber attnum)
 		return NULL;
 }
 
+/*
+ * get_relid_attribute_name
+ *
+ * Same as above routine get_attname(), except that error
+ * is handled by elog() instead of returning NULL.
+ */
+char *
+get_relid_attribute_name(Oid relid, AttrNumber attnum)
+{
+	char	   *attname;
+
+	attname = get_attname(relid, attnum);
+	if (attname == NULL)
+		elog(ERROR, "cache lookup failed for attribute %d of relation %u",
+			 attnum, relid);
+	return attname;
+}
+
 /*
  * get_attnum
  *
@@ -1443,7 +1460,7 @@ get_typtype(Oid typid)
  * get_typname
  *		Returns the name of a given type.
  *
- * Returns a palloc'd copy of the string, or NULL if no such relation.
+ * Returns a palloc'd copy of the string, or NULL if no such type.
  *
  * NOTE: since type name is not unique, be wary of code that uses this
  * for anything except preparing error messages.
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index ddaee15de5..2ff904510c 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -10,7 +10,7 @@
  * Written by Peter Eisentraut <peter_e@gmx.net>.
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/utils/misc/guc.c,v 1.148 2003/08/04 23:59:39 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/utils/misc/guc.c,v 1.149 2003/08/11 23:04:49 tgl Exp $
  *
  *--------------------------------------------------------------------
  */
@@ -3293,7 +3293,7 @@ GetPGVariableResultDesc(const char *name)
 
 		/* need a tuple descriptor representing a single TEXT column */
 		tupdesc = CreateTemplateTupleDesc(1, false);
-		TupleDescInitEntry(tupdesc, (AttrNumber) 1, (char *) varname,
+		TupleDescInitEntry(tupdesc, (AttrNumber) 1, varname,
 						   TEXTOID, -1, 0, false);
 	}
 	return tupdesc;
@@ -3333,7 +3333,7 @@ ShowGUCConfigOption(const char *name, DestReceiver *dest)
 
 	/* need a tuple descriptor representing a single TEXT column */
 	tupdesc = CreateTemplateTupleDesc(1, false);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 1, (char *) varname,
+	TupleDescInitEntry(tupdesc, (AttrNumber) 1, varname,
 					   TEXTOID, -1, 0, false);
 
 	/* prepare for projection of tuples */
diff --git a/src/include/access/tupdesc.h b/src/include/access/tupdesc.h
index c955689663..4ecb951a90 100644
--- a/src/include/access/tupdesc.h
+++ b/src/include/access/tupdesc.h
@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2003, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $Id: tupdesc.h,v 1.40 2003/08/04 02:40:10 momjian Exp $
+ * $Id: tupdesc.h,v 1.41 2003/08/11 23:04:50 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -70,7 +70,7 @@ extern bool equalTupleDescs(TupleDesc tupdesc1, TupleDesc tupdesc2);
 
 extern void TupleDescInitEntry(TupleDesc desc,
 				   AttrNumber attributeNumber,
-				   char *attributeName,
+				   const char *attributeName,
 				   Oid oidtypeid,
 				   int32 typmod,
 				   int attdim,
diff --git a/src/include/nodes/primnodes.h b/src/include/nodes/primnodes.h
index 49d5f49467..f6e4436d95 100644
--- a/src/include/nodes/primnodes.h
+++ b/src/include/nodes/primnodes.h
@@ -10,7 +10,7 @@
  * Portions Copyright (c) 1996-2003, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $Id: primnodes.h,v 1.90 2003/08/08 21:42:48 momjian Exp $
+ * $Id: primnodes.h,v 1.91 2003/08/11 23:04:50 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -31,13 +31,29 @@
  *
  * Notes:
  *
- * resno will normally be equal to the item's position in a targetlist,
- * but the code generally tries to avoid relying on that (eg, we avoid
- * using "nth()" rather than a search to find an item by resno).
- *
- * resname will be null if no name can easily be assigned to the column.
- * But it should never be null for user-visible columns (i.e., non-junk
- * columns in a toplevel targetlist).
+ * In a SELECT's targetlist, resno should always be equal to the item's
+ * ordinal position (counting from 1).  However, in an INSERT or UPDATE
+ * targetlist, resno represents the attribute number of the destination
+ * column for the item; so there may be missing or out-of-order resnos.
+ * In an UPDATE, it is even legal to have duplicated resnos; consider
+ *		UPDATE table SET arraycol[1] = ..., arraycol[2] = ..., ...
+ * The two meanings come together in the executor, because the planner
+ * transforms INSERT/UPDATE tlists into a normalized form with exactly
+ * one entry for each column of the destination table.  Before that's
+ * happened, however, it is risky to assume that resno == position.
+ * Generally get_tle_by_resno() should be used rather than nth() to fetch
+ * tlist entries by resno.
+ *
+ * resname is required to represent the correct column name in non-resjunk
+ * entries of top-level SELECT targetlists, since it will be used as the
+ * column title sent to the frontend.  In most other contexts it is only
+ * a debugging aid, and may be wrong or even NULL.  (In particular, it may
+ * be wrong in a tlist from a stored rule, if the referenced column has been
+ * renamed by ALTER TABLE since the rule was made.  Also, the planner tends
+ * to store NULL rather than look up a valid name for tlist entries in
+ * non-toplevel plan nodes.)  In resjunk entries, resname should be either
+ * a specific system-generated name (such as "ctid") or NULL; anything else
+ * risks confusing ExecGetJunkAttribute!
  *
  * ressortgroupref is used in the representation of ORDER BY and
  * GROUP BY items.	Targetlist entries with ressortgroupref=0 are not
@@ -53,13 +69,16 @@
  * a simple reference, these fields are zeroes.
  *
  * If resjunk is true then the column is a working column (such as a sort key)
- * that should be removed from the final output of the query.
+ * that should be removed from the final output of the query.  Resjunk columns
+ * must have resnos that cannot duplicate any regular column's resno.  Also
+ * note that there are places that assume resjunk columns come after non-junk
+ * columns.
  *--------------------
  */
 typedef struct Resdom
 {
 	NodeTag		type;
-	AttrNumber	resno;			/* attribute number (1..N) */
+	AttrNumber	resno;			/* attribute number (see notes above) */
 	Oid			restype;		/* type of the value */
 	int32		restypmod;		/* type-specific modifier of the value */
 	char	   *resname;		/* name of the column (could be NULL) */
diff --git a/src/include/utils/lsyscache.h b/src/include/utils/lsyscache.h
index c94e78eb49..4c9c073ade 100644
--- a/src/include/utils/lsyscache.h
+++ b/src/include/utils/lsyscache.h
@@ -6,7 +6,7 @@
  * Portions Copyright (c) 1996-2003, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $Id: lsyscache.h,v 1.79 2003/08/08 21:42:55 momjian Exp $
+ * $Id: lsyscache.h,v 1.80 2003/08/11 23:04:50 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -29,6 +29,7 @@ extern bool op_requires_recheck(Oid opno, Oid opclass);
 extern Oid	get_opclass_member(Oid opclass, int16 strategy);
 extern Oid	get_op_hash_function(Oid opno);
 extern char *get_attname(Oid relid, AttrNumber attnum);
+extern char *get_relid_attribute_name(Oid relid, AttrNumber attnum);
 extern AttrNumber get_attnum(Oid relid, const char *attname);
 extern Oid	get_atttype(Oid relid, AttrNumber attnum);
 extern int32 get_atttypmod(Oid relid, AttrNumber attnum);
-- 
2.40.0