Cause schema-qualified FROM items and schema-qualified variable references

to behave according to SQL92 (or according to my current understanding
of same, anyway).  Per pghackers discussion way back in March 2002:
thread 'Do FROM items of different schemas conflict?'

src/backend/catalog/namespace.c

@@ -13,7 +13,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/catalog/namespace.c,v 1.28 2002/08/06 05:40:44 ishii Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/catalog/namespace.c,v 1.29 2002/08/08 01:44:30 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -1080,7 +1080,7 @@ DeconstructQualifiedName(List *names,
  * Returns the namespace OID.  Raises elog if any problem.
  */
 Oid
-LookupExplicitNamespace(char *nspname)
+LookupExplicitNamespace(const char *nspname)
 {
 	Oid			namespaceId;
 	AclResult	aclresult;

src/backend/parser/parse_expr.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/parser/parse_expr.c,v 1.124 2002/08/04 06:46:12 thomas Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/parser/parse_expr.c,v 1.125 2002/08/08 01:44:30 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -709,6 +709,7 @@ transformColumnRef(ParseState *pstate, ColumnRef *cref)
 
 			/* Try to identify as an unqualified column */
 			node = colnameToVar(pstate, name);
+
 			if (node == NULL)
 			{
 				/*
@@ -716,11 +717,15 @@ transformColumnRef(ParseState *pstate, ColumnRef *cref)
 				 * try to find the name as a relation ... but not if
 				 * subscripts appear.  Note also that only relations
 				 * already entered into the rangetable will be recognized.
+				 *
+				 * This is a hack for backwards compatibility with PostQUEL-
+				 * inspired syntax.  The preferred form now is "rel.*".
 				 */
 				int		levels_up;
 
 				if (cref->indirection == NIL &&
-					refnameRangeTblEntry(pstate, name, &levels_up) != NULL)
+					refnameRangeTblEntry(pstate, NULL, name,
+										 &levels_up) != NULL)
 				{
 					rv = makeNode(RangeVar);
 					rv->relname = name;
@@ -748,7 +753,7 @@ transformColumnRef(ParseState *pstate, ColumnRef *cref)
 			}
 
 			/* Try to identify as a once-qualified column */
-			node = qualifiedNameToVar(pstate, name1, name2, true);
+			node = qualifiedNameToVar(pstate, NULL, name1, name2, true);
 			if (node == NULL)
 			{
 				/*
@@ -784,8 +789,7 @@ transformColumnRef(ParseState *pstate, ColumnRef *cref)
 			}
 
 			/* Try to identify as a twice-qualified column */
-			/* XXX do something with schema name here */
-			node = qualifiedNameToVar(pstate, name2, name3, true);
+			node = qualifiedNameToVar(pstate, name1, name2, name3, true);
 			if (node == NULL)
 			{
 				/* Try it as a function call */
@@ -825,8 +829,7 @@ transformColumnRef(ParseState *pstate, ColumnRef *cref)
 			}
 
 			/* Try to identify as a twice-qualified column */
-			/* XXX do something with schema name here */
-			node = qualifiedNameToVar(pstate, name3, name4, true);
+			node = qualifiedNameToVar(pstate, name2, name3, name4, true);
 			if (node == NULL)
 			{
 				/* Try it as a function call */

src/backend/parser/parse_func.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/parser/parse_func.c,v 1.133 2002/08/02 18:15:07 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/parser/parse_func.c,v 1.134 2002/08/08 01:44:30 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -51,6 +51,8 @@ static int match_argtypes(int nargs,
 static FieldSelect *setup_field_select(Node *input, char *attname, Oid relid);
 static FuncCandidateList func_select_candidate(int nargs, Oid *input_typeids,
 								  FuncCandidateList candidates);
+static void unknown_attribute(const char *schemaname, const char *relname,
+							  const char *attname);
 
 
 /*
@@ -80,7 +82,6 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 	Oid			funcid;
 	List	   *i;
 	Node	   *first_arg = NULL;
-	char	   *refname;
 	int			nargs = length(fargs);
 	int			argn;
 	Oid			oid_array[FUNC_MAX_ARGS];
@@ -121,10 +122,11 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 		if (IsA(first_arg, RangeVar))
 		{
 			/* First arg is a relation. This could be a projection. */
-			refname = ((RangeVar *) first_arg)->relname;
-
-			/* XXX WRONG: ignores possible qualification of argument */
-			retval = qualifiedNameToVar(pstate, refname, cname, true);
+			retval = qualifiedNameToVar(pstate,
+										((RangeVar *) first_arg)->schemaname,
+										((RangeVar *) first_arg)->relname,
+										cname,
+										true);
 			if (retval)
 				return retval;
 		}
@@ -156,16 +158,19 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 
 		if (IsA(arg, RangeVar))
 		{
+			char	   *schemaname;
+			char	   *relname;
 			RangeTblEntry *rte;
 			int			vnum;
 			int			sublevels_up;
 
 			/*
-			 * a relation
+			 * a relation: look it up in the range table, or add if needed
 			 */
-			refname = ((RangeVar *) arg)->relname;
+			schemaname = ((RangeVar *) arg)->schemaname;
+			relname = ((RangeVar *) arg)->relname;
 
-			rte = refnameRangeTblEntry(pstate, refname,
+			rte = refnameRangeTblEntry(pstate, schemaname, relname,
 									   &sublevels_up);
 
 			if (rte == NULL)
@@ -199,11 +204,11 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 					 * named tuple type
 					 */
 					if (is_column)
-						elog(ERROR, "No such attribute %s.%s",
-							 refname, strVal(lfirst(funcname)));
+						unknown_attribute(schemaname, relname,
+										  strVal(lfirst(funcname)));
 					else
 						elog(ERROR, "Cannot pass result of sub-select or join %s to a function",
-							 refname);
+							 relname);
 					toid = InvalidOid; /* keep compiler quiet */
 					break;
 			}
@@ -268,8 +273,9 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 
 			Assert(nargs == 1);
 			if (IsA(first_arg, RangeVar))
-				elog(ERROR, "No such attribute %s.%s",
-					 ((RangeVar *) first_arg)->relname, colname);
+				unknown_attribute(((RangeVar *) first_arg)->schemaname,
+								  ((RangeVar *) first_arg)->relname,
+								  colname);
 			relTypeId = exprType(first_arg);
 			if (!ISCOMPLEX(relTypeId))
 				elog(ERROR, "Attribute notation .%s applied to type %s, which is not a complex type",
@@ -1225,6 +1231,21 @@ ParseComplexProjection(ParseState *pstate,
 	return (Node *) fselect;
 }
 
+/*
+ * Simple helper routine for delivering "No such attribute" error message
+ */
+static void
+unknown_attribute(const char *schemaname, const char *relname,
+				  const char *attname)
+{
+	if (schemaname)
+		elog(ERROR, "No such attribute %s.%s.%s",
+			 schemaname, relname, attname);
+	else
+		elog(ERROR, "No such attribute %s.%s",
+			 relname, attname);
+}
+
 /*
  * Error message when function lookup fails that gives details of the
  * argument types

src/backend/parser/parse_relation.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/parser/parse_relation.c,v 1.75 2002/08/06 05:34:10 momjian Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/parser/parse_relation.c,v 1.76 2002/08/08 01:44:30 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -19,6 +19,7 @@
 #include "access/heapam.h"
 #include "access/htup.h"
 #include "catalog/heap.h"
+#include "catalog/namespace.h"
 #include "catalog/pg_type.h"
 #include "nodes/makefuncs.h"
 #include "parser/parsetree.h"
@@ -33,7 +34,11 @@
 
 
 static Node *scanNameSpaceForRefname(ParseState *pstate, Node *nsnode,
-						char *refname);
+						const char *refname);
+static Node *scanNameSpaceForRelid(ParseState *pstate, Node *nsnode,
+								   Oid relid);
+static void scanNameSpaceForConflict(ParseState *pstate, Node *nsnode,
+						 RangeTblEntry *rte1, const char *aliasname1);
 static Node *scanRTEForColumn(ParseState *pstate, RangeTblEntry *rte,
 				 char *colname);
 static bool isForUpdate(ParseState *pstate, char *refname);
@@ -45,26 +50,58 @@ static void warnAutoRange(ParseState *pstate, RangeVar *relation);
 
 /*
  * refnameRangeTblEntry
- *	  Given a refname, look to see if it matches any RTE.
- *	  If so, return a pointer to the RangeTblEntry.
- *	  Optionally get its nesting depth (0 = current).	If sublevels_up
- *	  is NULL, only consider items at the current nesting level.
+ *	  Given a possibly-qualified refname, look to see if it matches any RTE.
+ *	  If so, return a pointer to the RangeTblEntry; else return NULL.
+ *
+ *	  Optionally get RTE's nesting depth (0 = current) into *sublevels_up.
+ *	  If sublevels_up is NULL, only consider items at the current nesting
+ *	  level.
+ *
+ * An unqualified refname (schemaname == NULL) can match any RTE with matching
+ * alias, or matching unqualified relname in the case of alias-less relation
+ * RTEs.  It is possible that such a refname matches multiple RTEs in the
+ * nearest nesting level that has a match; if so, we report an error via elog.
+ *
+ * A qualified refname (schemaname != NULL) can only match a relation RTE
+ * that (a) has no alias and (b) is for the same relation identified by
+ * schemaname.refname.  In this case we convert schemaname.refname to a
+ * relation OID and search by relid, rather than by alias name.  This is
+ * peculiar, but it's what SQL92 says to do.
  */
 RangeTblEntry *
 refnameRangeTblEntry(ParseState *pstate,
-					 char *refname,
+					 const char *schemaname,
+					 const char *refname,
 					 int *sublevels_up)
 {
+	Oid			relId = InvalidOid;
+
 	if (sublevels_up)
 		*sublevels_up = 0;
 
+	if (schemaname != NULL)
+	{
+		Oid			namespaceId;
+
+		namespaceId = LookupExplicitNamespace(schemaname);
+		relId = get_relname_relid(refname, namespaceId);
+		if (!OidIsValid(relId))
+			return NULL;
+	}
+
 	while (pstate != NULL)
 	{
 		Node	   *nsnode;
 
-		nsnode = scanNameSpaceForRefname(pstate,
-										 (Node *) pstate->p_namespace,
-										 refname);
+		if (OidIsValid(relId))
+			nsnode = scanNameSpaceForRelid(pstate,
+										   (Node *) pstate->p_namespace,
+										   relId);
+		else
+			nsnode = scanNameSpaceForRefname(pstate,
+											 (Node *) pstate->p_namespace,
+											 refname);
+
 		if (nsnode)
 		{
 			/* should get an RTE or JoinExpr */
@@ -84,20 +121,19 @@ refnameRangeTblEntry(ParseState *pstate,
 }
 
 /*
- * Recursively search a namespace for an RTE or joinexpr with given refname.
+ * Recursively search a namespace for an RTE or joinexpr matching the
+ * given unqualified refname.  Return the node if a unique match, or NULL
+ * if no match.  Raise error if multiple matches.
  *
  * The top level of p_namespace is a list, and we recurse into any joins
- * that are not subqueries.  It is also possible to pass an individual
- * join subtree (useful when checking for name conflicts within a scope).
- *
- * Note: we do not worry about the possibility of multiple matches;
- * we assume the code that built the namespace checked for duplicates.
+ * that are not subqueries.
  */
 static Node *
 scanNameSpaceForRefname(ParseState *pstate, Node *nsnode,
-						char *refname)
+						const char *refname)
 {
 	Node	   *result = NULL;
+	Node	   *newresult;
 
 	if (nsnode == NULL)
 		return NULL;
@@ -126,8 +162,11 @@ scanNameSpaceForRefname(ParseState *pstate, Node *nsnode,
 			return NULL;
 		}
 		result = scanNameSpaceForRefname(pstate, j->larg, refname);
+		newresult = scanNameSpaceForRefname(pstate, j->rarg, refname);
 		if (!result)
-			result = scanNameSpaceForRefname(pstate, j->rarg, refname);
+			result = newresult;
+		else if (newresult)
+			elog(ERROR, "Table reference \"%s\" is ambiguous", refname);
 	}
 	else if (IsA(nsnode, List))
 	{
@@ -135,9 +174,11 @@ scanNameSpaceForRefname(ParseState *pstate, Node *nsnode,
 
 		foreach(l, (List *) nsnode)
 		{
-			result = scanNameSpaceForRefname(pstate, lfirst(l), refname);
-			if (result)
-				break;
+			newresult = scanNameSpaceForRefname(pstate, lfirst(l), refname);
+			if (!result)
+				result = newresult;
+			else if (newresult)
+				elog(ERROR, "Table reference \"%s\" is ambiguous", refname);
 		}
 	}
 	else
@@ -146,25 +187,89 @@ scanNameSpaceForRefname(ParseState *pstate, Node *nsnode,
 	return result;
 }
 
-/* Convenience subroutine for checkNameSpaceConflicts */
-static void
-scanNameSpaceForConflict(ParseState *pstate, Node *nsnode,
-						 char *refname)
+/*
+ * Recursively search a namespace for a relation RTE matching the
+ * given relation OID.  Return the node if a unique match, or NULL
+ * if no match.  Raise error if multiple matches (which shouldn't
+ * happen if the namespace was checked correctly when it was created).
+ *
+ * The top level of p_namespace is a list, and we recurse into any joins
+ * that are not subqueries.
+ *
+ * See the comments for refnameRangeTblEntry to understand why this
+ * acts the way it does.
+ */
+static Node *
+scanNameSpaceForRelid(ParseState *pstate, Node *nsnode, Oid relid)
 {
-	if (scanNameSpaceForRefname(pstate, nsnode, refname) != NULL)
-		elog(ERROR, "Table name \"%s\" specified more than once", refname);
+	Node	   *result = NULL;
+	Node	   *newresult;
+
+	if (nsnode == NULL)
+		return NULL;
+	if (IsA(nsnode, RangeTblRef))
+	{
+		int			varno = ((RangeTblRef *) nsnode)->rtindex;
+		RangeTblEntry *rte = rt_fetch(varno, pstate->p_rtable);
+
+		/* yes, the test for alias==NULL should be there... */
+		if (rte->rtekind == RTE_RELATION &&
+			rte->relid == relid &&
+			rte->alias == NULL)
+			result = (Node *) rte;
+	}
+	else if (IsA(nsnode, JoinExpr))
+	{
+		JoinExpr   *j = (JoinExpr *) nsnode;
+
+		if (j->alias)
+		{
+			/*
+			 * Tables within an aliased join are invisible from outside
+			 * the join, according to the scope rules of SQL92 (the join
+			 * is considered a subquery).  So, stop here.
+			 */
+			return NULL;
+		}
+		result = scanNameSpaceForRelid(pstate, j->larg, relid);
+		newresult = scanNameSpaceForRelid(pstate, j->rarg, relid);
+		if (!result)
+			result = newresult;
+		else if (newresult)
+			elog(ERROR, "Table reference %u is ambiguous", relid);
+	}
+	else if (IsA(nsnode, List))
+	{
+		List	   *l;
+
+		foreach(l, (List *) nsnode)
+		{
+			newresult = scanNameSpaceForRelid(pstate, lfirst(l), relid);
+			if (!result)
+				result = newresult;
+			else if (newresult)
+				elog(ERROR, "Table reference %u is ambiguous", relid);
+		}
+	}
+	else
+		elog(ERROR, "scanNameSpaceForRelid: unexpected node type %d",
+			 nodeTag(nsnode));
+	return result;
 }
 
 /*
- * Recursively check for refname conflicts between two namespaces or
+ * Recursively check for name conflicts between two namespaces or
  * namespace subtrees.	Raise an error if any is found.
  *
- * Works by recursively scanning namespace1 in the same way that
- * scanNameSpaceForRefname does, and then looking in namespace2 for
- * a match to each refname found in namespace1.
+ * Works by recursively scanning namespace1 for RTEs and join nodes,
+ * and for each one recursively scanning namespace2 for a match.
  *
  * Note: we assume that each given argument does not contain conflicts
  * itself; we just want to know if the two can be merged together.
+ *
+ * Per SQL92, two alias-less plain relation RTEs do not conflict even if
+ * they have the same eref->aliasname (ie, same relation name), if they
+ * are for different relation OIDs (implying they are in different schemas).
  */
 void
 checkNameSpaceConflicts(ParseState *pstate, Node *namespace1,
@@ -177,7 +282,12 @@ checkNameSpaceConflicts(ParseState *pstate, Node *namespace1,
 		int			varno = ((RangeTblRef *) namespace1)->rtindex;
 		RangeTblEntry *rte = rt_fetch(varno, pstate->p_rtable);
 
-		scanNameSpaceForConflict(pstate, namespace2, rte->eref->aliasname);
+		if (rte->rtekind == RTE_RELATION && rte->alias == NULL)
+			scanNameSpaceForConflict(pstate, namespace2,
+									 rte, rte->eref->aliasname);
+		else
+			scanNameSpaceForConflict(pstate, namespace2,
+									 NULL, rte->eref->aliasname);
 	}
 	else if (IsA(namespace1, JoinExpr))
 	{
@@ -185,7 +295,8 @@ checkNameSpaceConflicts(ParseState *pstate, Node *namespace1,
 
 		if (j->alias)
 		{
-			scanNameSpaceForConflict(pstate, namespace2, j->alias->aliasname);
+			scanNameSpaceForConflict(pstate, namespace2,
+									 NULL, j->alias->aliasname);
 
 			/*
 			 * Tables within an aliased join are invisible from outside
@@ -202,13 +313,70 @@ checkNameSpaceConflicts(ParseState *pstate, Node *namespace1,
 		List	   *l;
 
 		foreach(l, (List *) namespace1)
+		{
 			checkNameSpaceConflicts(pstate, lfirst(l), namespace2);
+		}
 	}
 	else
 		elog(ERROR, "checkNameSpaceConflicts: unexpected node type %d",
 			 nodeTag(namespace1));
 }
 
+/*
+ * Subroutine for checkNameSpaceConflicts: scan namespace2
+ */
+static void
+scanNameSpaceForConflict(ParseState *pstate, Node *nsnode,
+						 RangeTblEntry *rte1, const char *aliasname1)
+{
+	if (nsnode == NULL)
+		return;
+	if (IsA(nsnode, RangeTblRef))
+	{
+		int			varno = ((RangeTblRef *) nsnode)->rtindex;
+		RangeTblEntry *rte = rt_fetch(varno, pstate->p_rtable);
+
+		if (strcmp(rte->eref->aliasname, aliasname1) != 0)
+			return;				/* definitely no conflict */
+		if (rte->rtekind == RTE_RELATION && rte->alias == NULL &&
+			rte1 != NULL && rte->relid != rte1->relid)
+			return;				/* no conflict per SQL92 rule */
+		elog(ERROR, "Table name \"%s\" specified more than once",
+			 aliasname1);
+	}
+	else if (IsA(nsnode, JoinExpr))
+	{
+		JoinExpr   *j = (JoinExpr *) nsnode;
+
+		if (j->alias)
+		{
+			if (strcmp(j->alias->aliasname, aliasname1) == 0)
+				elog(ERROR, "Table name \"%s\" specified more than once",
+					 aliasname1);
+			/*
+			 * Tables within an aliased join are invisible from outside
+			 * the join, according to the scope rules of SQL92 (the join
+			 * is considered a subquery).  So, stop here.
+			 */
+			return;
+		}
+		scanNameSpaceForConflict(pstate, j->larg, rte1, aliasname1);
+		scanNameSpaceForConflict(pstate, j->rarg, rte1, aliasname1);
+	}
+	else if (IsA(nsnode, List))
+	{
+		List	   *l;
+
+		foreach(l, (List *) nsnode)
+		{
+			scanNameSpaceForConflict(pstate, lfirst(l), rte1, aliasname1);
+		}
+	}
+	else
+		elog(ERROR, "scanNameSpaceForConflict: unexpected node type %d",
+			 nodeTag(nsnode));
+}
+
 /*
  * given an RTE, return RT index (starting with 1) of the entry,
  * and optionally get its nesting depth (0 = current).	If sublevels_up
@@ -403,24 +571,29 @@ colnameToVar(ParseState *pstate, char *colname)
 
 /*
  * qualifiedNameToVar
- *	  Search for a qualified column name (refname + column name).
+ *	  Search for a qualified column name: either refname.colname or
+ *	  schemaname.relname.colname.
+ *
  *	  If found, return the appropriate Var node.
  *	  If not found, return NULL.  If the name proves ambiguous, raise error.
  */
 Node *
-qualifiedNameToVar(ParseState *pstate, char *refname, char *colname,
+qualifiedNameToVar(ParseState *pstate,
+				   char *schemaname,
+				   char *refname,
+				   char *colname,
 				   bool implicitRTEOK)
 {
 	RangeTblEntry *rte;
 	int			sublevels_up;
 
-	rte = refnameRangeTblEntry(pstate, refname, &sublevels_up);
+	rte = refnameRangeTblEntry(pstate, schemaname, refname, &sublevels_up);
 
 	if (rte == NULL)
 	{
 		if (!implicitRTEOK)
 			return NULL;
-		rte = addImplicitRTE(pstate, makeRangeVar(NULL, refname));
+		rte = addImplicitRTE(pstate, makeRangeVar(schemaname, refname));
 	}
 
 	return scanRTEForColumn(pstate, rte, colname);

src/backend/parser/parse_target.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/parser/parse_target.c,v 1.86 2002/08/02 18:15:07 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/parser/parse_target.c,v 1.87 2002/08/08 01:44:31 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -155,11 +155,11 @@ transformTargetList(ParseState *pstate, List *targetlist)
 						break;
 				}
 
-				/* XXX do something with schema name */
-				rte = refnameRangeTblEntry(pstate, relname,
+				rte = refnameRangeTblEntry(pstate, schemaname, relname,
 										   &sublevels_up);
 				if (rte == NULL)
-					rte = addImplicitRTE(pstate, makeRangeVar(NULL, relname));
+					rte = addImplicitRTE(pstate, makeRangeVar(schemaname,
+															  relname));
 
 				p_target = nconc(p_target,
 								 expandRelAttrs(pstate, rte));

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 1.112 2002/07/18 23:11:28 petere Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/utils/adt/ruleutils.c,v 1.113 2002/08/08 01:44:31 tgl Exp $
  *
  *	  This software is copyrighted by Jan Wieck - Hamburg.
  *
@@ -131,7 +131,9 @@ static Node *get_rule_sortgroupclause(SortClause *srt, List *tlist,
 						 bool force_colno,
 						 deparse_context *context);
 static void get_names_for_var(Var *var, deparse_context *context,
-				  char **refname, char **attname);
+				  char **schemaname, char **refname, char **attname);
+static RangeTblEntry *find_rte_by_refname(const char *refname,
+										  deparse_context *context);
 static void get_rule_expr(Node *node, deparse_context *context);
 static void get_oper_expr(Expr *expr, deparse_context *context);
 static void get_func_expr(Expr *expr, deparse_context *context);
@@ -1204,10 +1206,11 @@ get_basic_select_query(Query *query, deparse_context *context)
 		else
 		{
 			Var		   *var = (Var *) (tle->expr);
+			char	   *schemaname;
 			char	   *refname;
 			char	   *attname;
 
-			get_names_for_var(var, context, &refname, &attname);
+			get_names_for_var(var, context, &schemaname, &refname, &attname);
 			tell_as = (attname == NULL ||
 					   strcmp(attname, tle->resdom->resname) != 0);
 		}
@@ -1513,17 +1516,22 @@ get_utility_query_def(Query *query, deparse_context *context)
 
 
 /*
- * Get the relation refname and attname for a (possibly nonlocal) Var.
+ * Get the schemaname, refname and attname for a (possibly nonlocal) Var.
+ *
+ * schemaname is usually returned as NULL.  It will be non-null only if
+ * use of the unqualified refname would find the wrong RTE.
  *
  * refname will be returned as NULL if the Var references an unnamed join.
  * In this case the Var *must* be displayed without any qualification.
  *
  * attname will be returned as NULL if the Var represents a whole tuple
- * of the relation.
+ * of the relation.  (Typically we'd want to display the Var as "foo.*",
+ * but it's convenient to return NULL to make it easier for callers to
+ * distinguish this case.)
  */
 static void
 get_names_for_var(Var *var, deparse_context *context,
-				  char **refname, char **attname)
+				  char **schemaname, char **refname, char **attname)
 {
 	List	   *nslist = context->namespaces;
 	int			sup = var->varlevelsup;
@@ -1552,10 +1560,29 @@ get_names_for_var(Var *var, deparse_context *context,
 			 var->varno);
 
 	/* Emit results */
-	if (rte->rtekind == RTE_JOIN && rte->alias == NULL)
-		*refname = NULL;
-	else
-		*refname = rte->eref->aliasname;
+	*schemaname = NULL;			/* default assumptions */
+	*refname = rte->eref->aliasname;
+
+	/* Exceptions occur only if the RTE is alias-less */
+	if (rte->alias == NULL)
+	{
+		if (rte->rtekind == RTE_RELATION)
+		{
+			/*
+			 * It's possible that use of the bare refname would find another
+			 * more-closely-nested RTE, or be ambiguous, in which case
+			 * we need to specify the schemaname to avoid these errors.
+			 */
+			if (find_rte_by_refname(rte->eref->aliasname, context) != rte)
+				*schemaname =
+					get_namespace_name(get_rel_namespace(rte->relid));
+		}
+		else if (rte->rtekind == RTE_JOIN)
+		{
+			/* Unnamed join has neither schemaname nor refname */
+			*refname = NULL;
+		}
+	}
 
 	if (var->varattno == InvalidAttrNumber)
 		*attname = NULL;
@@ -1563,6 +1590,61 @@ get_names_for_var(Var *var, deparse_context *context,
 		*attname = get_rte_attribute_name(rte, var->varattno);
 }
 
+/*
+ * find_rte_by_refname		- look up an RTE by refname in a deparse context
+ *
+ * Returns NULL if there is no matching RTE or the refname is ambiguous.
+ *
+ * NOTE: this code is not really correct since it does not take account of
+ * the fact that not all the RTEs in a rangetable may be visible from the
+ * point where a Var reference appears.  For the purposes we need, however,
+ * the only consequence of a false match is that we might stick a schema
+ * qualifier on a Var that doesn't really need it.  So it seems close
+ * enough.
+ */
+static RangeTblEntry *
+find_rte_by_refname(const char *refname, deparse_context *context)
+{
+	RangeTblEntry *result = NULL;
+	List	   *nslist;
+
+	foreach(nslist, context->namespaces)
+	{
+		deparse_namespace *dpns = (deparse_namespace *) lfirst(nslist);
+		List	   *rtlist;
+
+		foreach(rtlist, dpns->rtable)
+		{
+			RangeTblEntry *rte = (RangeTblEntry *) lfirst(rtlist);
+
+			if (strcmp(rte->eref->aliasname, refname) == 0)
+			{
+				if (result)
+					return NULL; /* it's ambiguous */
+				result = rte;
+			}
+		}
+		if (dpns->outer_rte &&
+			strcmp(dpns->outer_rte->eref->aliasname, refname) == 0)
+		{
+			if (result)
+				return NULL;	/* it's ambiguous */
+			result = dpns->outer_rte;
+		}
+		if (dpns->inner_rte &&
+			strcmp(dpns->inner_rte->eref->aliasname, refname) == 0)
+		{
+			if (result)
+				return NULL;	/* it's ambiguous */
+			result = dpns->inner_rte;
+		}
+		if (result)
+			break;
+	}
+	return result;
+}
+
+
 /* ----------
  * get_rule_expr			- Parse back an expression
  * ----------
@@ -1592,24 +1674,30 @@ get_rule_expr(Node *node, deparse_context *context)
 		case T_Var:
 			{
 				Var		   *var = (Var *) node;
+				char	   *schemaname;
 				char	   *refname;
 				char	   *attname;
 
-				get_names_for_var(var, context, &refname, &attname);
+				get_names_for_var(var, context,
+								  &schemaname, &refname, &attname);
 				if (refname && (context->varprefix || attname == NULL))
 				{
+					if (schemaname)
+						appendStringInfo(buf, "%s.",
+										 quote_identifier(schemaname));
+
 					if (strcmp(refname, "*NEW*") == 0)
-						appendStringInfo(buf, "new");
+						appendStringInfo(buf, "new.");
 					else if (strcmp(refname, "*OLD*") == 0)
-						appendStringInfo(buf, "old");
+						appendStringInfo(buf, "old.");
 					else
-						appendStringInfo(buf, "%s",
+						appendStringInfo(buf, "%s.",
 										 quote_identifier(refname));
-					if (attname)
-						appendStringInfoChar(buf, '.');
 				}
 				if (attname)
 					appendStringInfo(buf, "%s", quote_identifier(attname));
+				else
+					appendStringInfo(buf, "*");
 			}
 			break;
 

src/include/catalog/namespace.h

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $Id: namespace.h,v 1.18 2002/08/06 05:40:45 ishii Exp $
+ * $Id: namespace.h,v 1.19 2002/08/08 01:44:31 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -69,7 +69,7 @@ extern bool OpclassIsVisible(Oid opcid);
 extern void DeconstructQualifiedName(List *names,
 									 char **nspname_p,
 									 char **objname_p);
-extern Oid	LookupExplicitNamespace(char *nspname);
+extern Oid	LookupExplicitNamespace(const char *nspname);
 
 extern Oid	QualifiedNameGetCreationNamespace(List *names, char **objname_p);
 extern RangeVar *makeRangeVarFromNameList(List *names);

src/include/parser/parse_relation.h

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $Id: parse_relation.h,v 1.37 2002/08/05 02:30:50 tgl Exp $
+ * $Id: parse_relation.h,v 1.38 2002/08/08 01:44:31 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -17,7 +17,8 @@
 #include "parser/parse_node.h"
 
 extern RangeTblEntry *refnameRangeTblEntry(ParseState *pstate,
-						char *refname,
+						const char *schemaname,
+						const char *refname,
 						int *sublevels_up);
 extern void checkNameSpaceConflicts(ParseState *pstate, Node *namespace1,
 						Node *namespace2);
@@ -25,8 +26,11 @@ extern int RTERangeTablePosn(ParseState *pstate,
 				  RangeTblEntry *rte,
 				  int *sublevels_up);
 extern Node *colnameToVar(ParseState *pstate, char *colname);
-extern Node *qualifiedNameToVar(ParseState *pstate, char *refname,
-				   char *colname, bool implicitRTEOK);
+extern Node *qualifiedNameToVar(ParseState *pstate,
+								char *schemaname,
+								char *refname,
+								char *colname,
+								bool implicitRTEOK);
 extern RangeTblEntry *addRangeTableEntry(ParseState *pstate,
 				   RangeVar *relation,
 				   Alias *alias,