Add CREATE OR REPLACE FUNCTION syntax to allow replacing a function

definition without changing the function's OID, thereby not breaking
rules, views, triggers, etc that depend on it.  From Gavin Sherry.

src/backend/catalog/pg_proc.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/catalog/pg_proc.c,v 1.59 2001/09/08 01:10:19 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/catalog/pg_proc.c,v 1.60 2001/10/02 21:39:35 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -41,6 +41,7 @@ static void checkretval(Oid rettype, List *queryTreeList);
  */
 Oid
 ProcedureCreate(char *procedureName,
+				bool replace,
 				bool returnsSet,
 				char *returnTypeName,
 				char *languageName,
@@ -58,10 +59,12 @@ ProcedureCreate(char *procedureName,
 	int			i;
 	Relation	rel;
 	HeapTuple	tup;
+	HeapTuple	oldtup;
 	bool		defined;
 	uint16		parameterCount;
 	char		nulls[Natts_pg_proc];
 	Datum		values[Natts_pg_proc];
+	char		replaces[Natts_pg_proc];
 	Oid			languageObjectId;
 	Oid			typeObjectId;
 	List	   *x;
@@ -120,15 +123,6 @@ ProcedureCreate(char *procedureName,
 		typev[parameterCount++] = toid;
 	}
 
-	/* Check for duplicate definition */
-	if (SearchSysCacheExists(PROCNAME,
-							 PointerGetDatum(procedureName),
-							 UInt16GetDatum(parameterCount),
-							 PointerGetDatum(typev),
-							 0))
-		elog(ERROR, "function %s already exists with same argument types",
-			 procedureName);
-
 	if (languageObjectId == SQLlanguageId)
 	{
 
@@ -260,13 +254,14 @@ ProcedureCreate(char *procedureName,
 	}
 
 	/*
-	 * All seems OK; prepare the tuple to be inserted into pg_proc.
+	 * All seems OK; prepare the data to be inserted into pg_proc.
 	 */
 
 	for (i = 0; i < Natts_pg_proc; ++i)
 	{
 		nulls[i] = ' ';
 		values[i] = (Datum) NULL;
+		replaces[i] = 'r';
 	}
 
 	i = 0;
@@ -293,14 +288,49 @@ ProcedureCreate(char *procedureName,
 									  CStringGetDatum(probin));
 
 	rel = heap_openr(ProcedureRelationName, RowExclusiveLock);
-
 	tupDesc = rel->rd_att;
-	tup = heap_formtuple(tupDesc,
-						 values,
-						 nulls);
 
-	heap_insert(rel, tup);
+	/* Check for pre-existing definition */
+	oldtup = SearchSysCache(PROCNAME,
+							PointerGetDatum(procedureName),
+							UInt16GetDatum(parameterCount),
+							PointerGetDatum(typev),
+							0);
 
+	if (HeapTupleIsValid(oldtup))
+	{
+		/* There is one; okay to replace it? */
+		Form_pg_proc	oldproc = (Form_pg_proc) GETSTRUCT(oldtup);
+
+		if (!replace)
+			elog(ERROR, "function %s already exists with same argument types",
+				 procedureName);
+		if (GetUserId() != oldproc->proowner && !superuser())
+			elog(ERROR, "ProcedureCreate: you do not have permission to replace function %s",
+				 procedureName);
+		/*
+		 * Not okay to change the return type of the existing proc, since
+		 * existing rules, views, etc may depend on the return type.
+		 */
+		if (typeObjectId != oldproc->prorettype ||
+			returnsSet != oldproc->proretset)
+			elog(ERROR, "ProcedureCreate: cannot change return type of existing function."
+				 "\n\tUse DROP FUNCTION first.");
+
+		/* Okay, do it... */
+ 		tup = heap_modifytuple(oldtup, rel, values, nulls, replaces);
+ 	   	simple_heap_update(rel, &tup->t_self, tup);
+
+		ReleaseSysCache(oldtup);
+	}
+	else
+	{
+		/* Creating a new procedure */
+		tup = heap_formtuple(tupDesc, values, nulls);
+		heap_insert(rel, tup);
+	}
+
+	/* Need to update indices for either the insert or update case */
 	if (RelationGetForm(rel)->relhasindex)
 	{
 		Relation	idescs[Num_pg_proc_indices];
@@ -309,9 +339,12 @@ ProcedureCreate(char *procedureName,
 		CatalogIndexInsert(idescs, Num_pg_proc_indices, rel, tup);
 		CatalogCloseIndices(Num_pg_proc_indices, idescs);
 	}
-	heap_close(rel, RowExclusiveLock);
+
 	retval = tup->t_data->t_oid;
 	heap_freetuple(tup);
+
+	heap_close(rel, RowExclusiveLock);
+
 	return retval;
 }
 

src/backend/commands/define.c

@@ -10,7 +10,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/commands/define.c,v 1.60 2001/09/08 01:10:20 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/commands/define.c,v 1.61 2001/10/02 21:39:35 tgl Exp $
  *
  * DESCRIPTION
  *	  The "DefineFoo" routines take the parse tree and pick out the
@@ -324,6 +324,7 @@ CreateFunction(ProcedureStmt *stmt)
 	 * to do so, go ahead and create the function.
 	 */
 	ProcedureCreate(stmt->funcname,
+					stmt->replace,
 					returnsSet,
 					prorettype,
 					languageName,

src/backend/nodes/copyfuncs.c

@@ -15,7 +15,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/nodes/copyfuncs.c,v 1.156 2001/09/18 01:59:06 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/nodes/copyfuncs.c,v 1.157 2001/10/02 21:39:35 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -2071,6 +2071,7 @@ _copyProcedureStmt(ProcedureStmt *from)
 {
 	ProcedureStmt *newnode = makeNode(ProcedureStmt);
 
+	newnode->replace = from->replace;
 	newnode->funcname = pstrdup(from->funcname);
 	Node_Copy(from, newnode, argTypes);
 	Node_Copy(from, newnode, returnType);

src/backend/nodes/equalfuncs.c

@@ -20,7 +20,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/nodes/equalfuncs.c,v 1.104 2001/09/18 01:59:06 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/nodes/equalfuncs.c,v 1.105 2001/10/02 21:39:35 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -941,6 +941,8 @@ _equalIndexStmt(IndexStmt *a, IndexStmt *b)
 static bool
 _equalProcedureStmt(ProcedureStmt *a, ProcedureStmt *b)
 {
+	if (a->replace != b->replace)
+		return false;
 	if (!equalstr(a->funcname, b->funcname))
 		return false;
 	if (!equal(a->argTypes, b->argTypes))

src/backend/parser/gram.y

@@ -11,7 +11,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/parser/gram.y,v 2.255 2001/10/01 04:19:18 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/parser/gram.y,v 2.256 2001/10/02 21:39:35 tgl Exp $
  *
  * HISTORY
  *	  AUTHOR			DATE			MAJOR EVENT
@@ -151,7 +151,7 @@ static void doNegateFloat(Value *v);
 %type <list>	createdb_opt_list, createdb_opt_item
 
 %type <ival>	opt_lock, lock_type
-%type <boolean>	opt_force
+%type <boolean>	opt_force, opt_or_replace
 
 %type <list>	user_list
 
@@ -321,13 +321,13 @@ static void doNegateFloat(Value *v);
 		VALUES, VARCHAR, VARYING, VIEW,
 		WHEN, WHERE, WITH, WORK, YEAR_P, ZONE
 
-/* Keywords (in SQL3 reserved words) */
+/* Keywords (in SQL99 reserved words) */
 %token	CHAIN, CHARACTERISTICS,
 		DEFERRABLE, DEFERRED,
 		IMMEDIATE, INITIALLY, INOUT,
 		OFF, OUT,
 		PATH_P, PENDANT,
-		RESTRICT,
+		REPLACE, RESTRICT,
         TRIGGER,
 		WITHOUT
 
@@ -2497,33 +2497,32 @@ RecipeStmt:  EXECUTE RECIPE recipe_name
 /*****************************************************************************
  *
  *		QUERY:
- *				define function <fname>
+ *				create [or replace] function <fname>
  *						[(<type-1> { , <type-n>})]
  *						returns <type-r>
  *						as <filename or code in language as appropriate>
- *						language <lang> [with
- *						[  arch_pct = <percentage | pre-defined>]
- *						[, disk_pct = <percentage | pre-defined>]
- *						[, byte_pct = <percentage | pre-defined>]
- *						[, perbyte_cpu = <int | pre-defined>]
- *						[, percall_cpu = <int | pre-defined>]
- *						[, iscachable] ]
+ *						language <lang> [with parameters]
  *
  *****************************************************************************/
 
-ProcedureStmt:	CREATE FUNCTION func_name func_args
+ProcedureStmt:	CREATE opt_or_replace FUNCTION func_name func_args
 			 RETURNS func_return AS func_as LANGUAGE ColId_or_Sconst opt_with
 				{
 					ProcedureStmt *n = makeNode(ProcedureStmt);
-					n->funcname = $3;
-					n->argTypes = $4;
-					n->returnType = (Node *)$6;
-					n->withClause = $11;
-					n->as = $8;
-					n->language = $10;
+					n->replace = $2;
+					n->funcname = $4;
+					n->argTypes = $5;
+					n->returnType = (Node *) $7;
+					n->withClause = $12;
+					n->as = $9;
+					n->language = $11;
 					$$ = (Node *)n;
 				};
 
+opt_or_replace:  OR REPLACE						{ $$ = TRUE; }
+		| /*EMPTY*/								{ $$ = FALSE; }
+		;
+
 opt_with:  WITH definition						{ $$ = $2; }
 		| /*EMPTY*/								{ $$ = NIL; }
 		;
@@ -5682,6 +5681,7 @@ TokenId:  ABSOLUTE						{ $$ = "absolute"; }
 		| REINDEX						{ $$ = "reindex"; }
 		| RELATIVE						{ $$ = "relative"; }
 		| RENAME						{ $$ = "rename"; }
+		| REPLACE						{ $$ = "replace"; }
 		| RESTRICT						{ $$ = "restrict"; }
 		| RETURNS						{ $$ = "returns"; }
 		| REVOKE						{ $$ = "revoke"; }

src/backend/parser/keywords.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/parser/keywords.c,v 1.97 2001/08/26 16:56:00 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/parser/keywords.c,v 1.98 2001/10/02 21:39:35 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -216,6 +216,7 @@ static ScanKeyword ScanKeywords[] = {
 	{"reindex", REINDEX},
 	{"relative", RELATIVE},
 	{"rename", RENAME},
+	{"replace", REPLACE},
 	{"reset", RESET},
 	{"restrict", RESTRICT},
 	{"returns", RETURNS},

src/backend/utils/adt/sets.c

@@ -10,7 +10,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/utils/adt/Attic/sets.c,v 1.38 2001/09/08 01:10:20 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/utils/adt/Attic/sets.c,v 1.39 2001/10/02 21:39:35 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -51,6 +51,7 @@ SetDefine(char *querystr, char *typename)
 	char		repl[Natts_pg_proc];
 
 	setoid = ProcedureCreate(procname,	/* changed below, after oid known */
+							 false,		/* don't replace */
 							 true,		/* returnsSet */
 							 typename,	/* returnTypeName */
 							 "sql",		/* languageName */