The attached patch cleans up the implementation of the TRUNCATE command;

in the current code, the authentication logic (check user, check the
relation we're operating on, etc) is done in tcop/utility.c, whereas the
actual TRUNCATE command in done in TruncateRelation() in
commands/createinh.c (which is really just a wrapper over
heap_truncate() in catalog/heap.c). This patch moves the authentication
logic into TruncateRelation(), as well as making some minor code
cleanups.

Neil Conway

Author: bmomjian

src/backend/catalog/heap.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/catalog/heap.c,v 1.187 2002/03/19 02:18:14 momjian Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/catalog/heap.c,v 1.188 2002/03/19 02:58:19 momjian Exp $
  *
  *
  * INTERFACE ROUTINES
@@ -1057,7 +1057,7 @@ RelationTruncateIndexes(Oid heapId)
  */
 
 void
-heap_truncate(char *relname)
+heap_truncate(const char *relname)
 {
 	Relation	rel;
 	Oid			rid;

src/backend/commands/creatinh.c

@@ -8,14 +8,15 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/commands/Attic/creatinh.c,v 1.86 2002/03/19 02:18:15 momjian Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/commands/Attic/creatinh.c,v 1.87 2002/03/19 02:58:19 momjian Exp $
  *
  *-------------------------------------------------------------------------
  */
 
 #include "postgres.h"
 
 #include "access/heapam.h"
+#include "catalog/catalog.h"
 #include "catalog/catname.h"
 #include "catalog/indexing.h"
 #include "catalog/heap.h"
@@ -221,7 +222,7 @@ DefineRelation(CreateStmt *stmt, char relkind)
  * themselves will be destroyed, too.
  */
 void
-RemoveRelation(char *name)
+RemoveRelation(const char *name)
 {
 	AssertArg(name);
 	heap_drop_with_catalog(name, allowSystemTableMods);
@@ -238,10 +239,34 @@ RemoveRelation(char *name)
  *				  Rows are removed, indices are truncated and reconstructed.
  */
 void
-TruncateRelation(char *name)
+TruncateRelation(const char *relname)
 {
-	AssertArg(name);
-	heap_truncate(name);
+	Relation	rel;
+
+	AssertArg(relname);
+
+	if (!allowSystemTableMods && IsSystemRelationName(relname))
+		elog(ERROR, "TRUNCATE cannot be used on system tables. '%s' is a system table",
+			 relname);
+
+	if (!pg_ownercheck(GetUserId(), relname, RELNAME))
+		elog(ERROR, "you do not own relation \"%s\"", relname);
+
+	/* Grab exclusive lock in preparation for truncate */
+	rel = heap_openr(relname, AccessExclusiveLock);
+
+	if (rel->rd_rel->relkind == RELKIND_SEQUENCE)
+		elog(ERROR, "TRUNCATE cannot be used on sequences. '%s' is a sequence",
+			 relname);
+
+	if (rel->rd_rel->relkind == RELKIND_VIEW)
+		elog(ERROR, "TRUNCATE cannot be used on views. '%s' is a view",
+			 relname);
+
+	/* Keep the lock until transaction commit */
+	heap_close(rel, NoLock);
+
+	heap_truncate(relname);
 }
 
 

src/backend/tcop/utility.c

@@ -10,7 +10,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/tcop/utility.c,v 1.133 2002/03/19 02:18:20 momjian Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/tcop/utility.c,v 1.134 2002/03/19 02:58:19 momjian Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -216,9 +216,7 @@ ProcessUtility(Node *parsetree,
 			break;
 
 			/*
-			 * ******************************** relation and attribute
-			 * manipulation ********************************
-			 *
+			 * relation and attribute manipulation
 			 */
 		case T_CreateStmt:
 			DefineRelation((CreateStmt *) parsetree, RELKIND_RELATION);
@@ -301,26 +299,7 @@ ProcessUtility(Node *parsetree,
 
 		case T_TruncateStmt:
 			{
-				Relation	rel;
-
-				relname = ((TruncateStmt *) parsetree)->relName;
-				if (!allowSystemTableMods && IsSystemRelationName(relname))
-					elog(ERROR, "TRUNCATE cannot be used on system tables. '%s' is a system table",
-						 relname);
-
-				/* Grab exclusive lock in preparation for truncate... */
-				rel = heap_openr(relname, AccessExclusiveLock);
-				if (rel->rd_rel->relkind == RELKIND_SEQUENCE)
-					elog(ERROR, "TRUNCATE cannot be used on sequences. '%s' is a sequence",
-						 relname);
-				if (rel->rd_rel->relkind == RELKIND_VIEW)
-					elog(ERROR, "TRUNCATE cannot be used on views. '%s' is a view",
-						 relname);
-				heap_close(rel, NoLock);
-
-				if (!pg_ownercheck(GetUserId(), relname, RELNAME))
-					elog(ERROR, "you do not own class \"%s\"", relname);
-				TruncateRelation(relname);
+				TruncateRelation(((TruncateStmt *) parsetree)->relName);
 			}
 			break;
 

src/include/catalog/heap.h

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2001, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $Id: heap.h,v 1.44 2002/03/19 02:18:22 momjian Exp $
+ * $Id: heap.h,v 1.45 2002/03/19 02:58:19 momjian Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -41,7 +41,7 @@ extern Oid heap_create_with_catalog(char *relname, TupleDesc tupdesc,
 extern void heap_drop_with_catalog(const char *relname,
 					   bool allow_system_table_mods);
 
-extern void heap_truncate(char *relname);
+extern void heap_truncate(const char *relname);
 
 extern void AddRelationRawConstraints(Relation rel,
 						  List *rawColDefaults,

src/include/commands/creatinh.h

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2001, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $Id: creatinh.h,v 1.17 2001/11/05 17:46:33 momjian Exp $
+ * $Id: creatinh.h,v 1.18 2002/03/19 02:58:20 momjian Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -17,7 +17,7 @@
 #include "nodes/parsenodes.h"
 
 extern void DefineRelation(CreateStmt *stmt, char relkind);
-extern void RemoveRelation(char *name);
-extern void TruncateRelation(char *name);
+extern void RemoveRelation(const char *name);
+extern void TruncateRelation(const char *name);
 
 #endif   /* CREATINH_H */