Allow ALTER FUNCTION to change a function's strictness, volatility, and

whether or not it is a security definer. Changing a function's strictness
is required by SQL2003, and the other capabilities make sense. Also, allow
an optional RESTRICT noise word to be specified, for SQL conformance.

Some trivial regression tests added and the documentation has been
updated.

10 files changed, 307 insertions, 67 deletions

diff --git a/src/backend/commands/functioncmds.c b/src/backend/commands/functioncmds.c
index e2afbce1029..cbe14d130be 100644
--- a/src/backend/commands/functioncmds.c
+++ b/src/backend/commands/functioncmds.c
@@ -3,14 +3,14 @@
  * functioncmds.c
  *
  *	  Routines for CREATE and DROP FUNCTION commands and CREATE and DROP
- *		  CAST commands.
+ *	  CAST commands.
  *
  * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/commands/functioncmds.c,v 1.55 2005/03/13 05:19:26 neilc Exp $
+ *	  $PostgreSQL: pgsql/src/backend/commands/functioncmds.c,v 1.56 2005/03/14 00:19:36 neilc Exp $
  *
  * DESCRIPTION
  *	  These routines take the parse tree and pick out the
@@ -195,12 +195,75 @@ examine_parameter_list(List *parameter, Oid languageOid,
 	return parameterCount;
 }
 
+/*
+ * Recognize one of the options that can be passed to both CREATE
+ * FUNCTION and ALTER FUNCTION and return it via one of the out
+ * parameters. Returns true if the passed option was recognized. If
+ * the out parameter we were going to assign to points to non-NULL,
+ * raise a duplicate error.
+ */
+static bool
+compute_common_attribute(DefElem *defel,
+						 DefElem **volatility_item,
+						 DefElem **strict_item,
+						 DefElem **security_item)
+{
+	if (strcmp(defel->defname, "volatility") == 0)
+	{
+		if (*volatility_item)
+			goto duplicate_error;
+
+		*volatility_item = defel;
+	}
+	else if (strcmp(defel->defname, "strict") == 0)
+	{
+		if (*strict_item)
+			goto duplicate_error;
+
+		*strict_item = defel;
+	}
+	else if (strcmp(defel->defname, "security") == 0)
+	{
+		if (*security_item)
+			goto duplicate_error;
+
+		*security_item = defel;
+	}
+	else
+		return false;
+
+	/* Recognized an option */
+	return true;
+
+duplicate_error:
+	ereport(ERROR,
+			(errcode(ERRCODE_SYNTAX_ERROR),
+			 errmsg("conflicting or redundant options")));
+	return false; /* keep compiler quiet */
+}
+
+static char
+interpret_func_volatility(DefElem *defel)
+{
+	char *str = strVal(defel->arg);
+
+	if (strcmp(str, "immutable") == 0)
+		return PROVOLATILE_IMMUTABLE;
+	else if (strcmp(str, "stable") == 0)
+		return PROVOLATILE_STABLE;
+	else if (strcmp(str, "volatile") == 0)
+		return PROVOLATILE_VOLATILE;
+	else
+	{
+		elog(ERROR, "invalid volatility \"%s\"", str);
+		return 0; /* keep compiler quiet */
+	}
+}
 
 /*
  * Dissect the list of options assembled in gram.y into function
  * attributes.
  */
-
 static void
 compute_attributes_sql_style(List *options,
 							 List **as,
@@ -236,29 +299,13 @@ compute_attributes_sql_style(List *options,
 						 errmsg("conflicting or redundant options")));
 			language_item = defel;
 		}
-		else if (strcmp(defel->defname, "volatility") == 0)
+		else if (compute_common_attribute(defel,
+										  &volatility_item,
+										  &strict_item,
+										  &security_item))
 		{
-			if (volatility_item)
-				ereport(ERROR,
-						(errcode(ERRCODE_SYNTAX_ERROR),
-						 errmsg("conflicting or redundant options")));
-			volatility_item = defel;
-		}
-		else if (strcmp(defel->defname, "strict") == 0)
-		{
-			if (strict_item)
-				ereport(ERROR,
-						(errcode(ERRCODE_SYNTAX_ERROR),
-						 errmsg("conflicting or redundant options")));
-			strict_item = defel;
-		}
-		else if (strcmp(defel->defname, "security") == 0)
-		{
-			if (security_item)
-				ereport(ERROR,
-						(errcode(ERRCODE_SYNTAX_ERROR),
-						 errmsg("conflicting or redundant options")));
-			security_item = defel;
+			/* recognized common option */
+			continue;
 		}
 		else
 			elog(ERROR, "option \"%s\" not recognized",
@@ -280,18 +327,7 @@ compute_attributes_sql_style(List *options,
 				 errmsg("no language specified")));
 
 	if (volatility_item)
-	{
-		if (strcmp(strVal(volatility_item->arg), "immutable") == 0)
-			*volatility_p = PROVOLATILE_IMMUTABLE;
-		else if (strcmp(strVal(volatility_item->arg), "stable") == 0)
-			*volatility_p = PROVOLATILE_STABLE;
-		else if (strcmp(strVal(volatility_item->arg), "volatile") == 0)
-			*volatility_p = PROVOLATILE_VOLATILE;
-		else
-			elog(ERROR, "invalid volatility \"%s\"",
-				 strVal(volatility_item->arg));
-	}
-
+		*volatility_p = interpret_func_volatility(volatility_item);
 	if (strict_item)
 		*strict_p = intVal(strict_item->arg);
 	if (security_item)
@@ -301,7 +337,7 @@ compute_attributes_sql_style(List *options,
 
 /*-------------
  *	 Interpret the parameters *parameters and return their contents via
- *	 out parameters *isStrict_p and *volatility_p.
+ *	 *isStrict_p and *volatility_p.
  *
  *	These parameters supply optional information about a function.
  *	All have defaults if not specified. Parameters:
@@ -347,9 +383,7 @@ compute_attributes_with_style(List *parameters, bool *isStrict_p, char *volatili
  * In all other cases
  *
  *	   AS <object reference, or sql code>
- *
  */
-
 static void
 interpret_AS_clause(Oid languageOid, const char *languageName, List *as,
 					char **prosrc_str_p, char **probin_str_p)
@@ -799,7 +833,74 @@ AlterFunctionOwner(List *name, List *argtypes, AclId newOwnerSysId)
 	heap_close(rel, NoLock);
 }
 
+/*
+ * Implements the ALTER FUNCTION utility command (except for the
+ * RENAME and OWNER clauses, which are handled as part of the generic
+ * ALTER framework).
+ */
+void
+AlterFunction(AlterFunctionStmt *stmt)
+{
+	HeapTuple tup;
+	Oid funcOid;
+	Form_pg_proc procForm;
+	Relation rel;
+	ListCell *l;
+	DefElem *volatility_item = NULL;
+	DefElem *strict_item = NULL;
+	DefElem *security_def_item = NULL;
+
+	rel = heap_openr(ProcedureRelationName, RowExclusiveLock);
+
+	funcOid = LookupFuncNameTypeNames(stmt->func->funcname,
+									  stmt->func->funcargs,
+									  false);
+
+	tup = SearchSysCacheCopy(PROCOID,
+							 ObjectIdGetDatum(funcOid),
+							 0, 0, 0);
+	if (!HeapTupleIsValid(tup)) /* should not happen */
+		elog(ERROR, "cache lookup failed for function %u", funcOid);
+
+	procForm = (Form_pg_proc) GETSTRUCT(tup);
 
+	/* Permission check: must own function */
+	if (!pg_proc_ownercheck(funcOid, GetUserId()))
+		aclcheck_error(ACLCHECK_NOT_OWNER, ACL_KIND_PROC,
+					   NameListToString(stmt->func->funcname));
+
+	if (procForm->proisagg)
+		ereport(ERROR,
+				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
+				 errmsg("\"%s\" is an aggregate function",
+						NameListToString(stmt->func->funcname))));
+
+	/* Examine requested actions. */
+	foreach (l, stmt->actions)
+	{
+		DefElem *defel = (DefElem *) lfirst(l);
+
+		if (compute_common_attribute(defel,
+									 &volatility_item,
+									 &strict_item,
+									 &security_def_item) == false)
+			elog(ERROR, "option \"%s\" not recognized", defel->defname);
+	}
+
+	if (volatility_item)
+		procForm->provolatile = interpret_func_volatility(volatility_item);
+	if (strict_item)
+		procForm->proisstrict = intVal(strict_item->arg);
+	if (security_def_item)
+		procForm->prosecdef = intVal(security_def_item->arg);
+
+	/* Do the update */
+	simple_heap_update(rel, &tup->t_self, tup);
+	CatalogUpdateIndexes(rel, tup);
+
+	heap_close(rel, NoLock);
+	heap_freetuple(tup);
+}
 
 /*
  * SetFunctionReturnType - change declared return type of a function
diff --git a/src/backend/nodes/copyfuncs.c b/src/backend/nodes/copyfuncs.c
index 4acf02908b6..92f7168ae9f 100644
--- a/src/backend/nodes/copyfuncs.c
+++ b/src/backend/nodes/copyfuncs.c
@@ -15,7 +15,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/nodes/copyfuncs.c,v 1.297 2005/03/10 23:21:21 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/nodes/copyfuncs.c,v 1.298 2005/03/14 00:19:36 neilc Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -1892,6 +1892,17 @@ _copyFunctionParameter(FunctionParameter *from)
 	return newnode;
 }
 
+static AlterFunctionStmt *
+_copyAlterFunctionStmt(AlterFunctionStmt *from)
+{
+	AlterFunctionStmt *newnode = makeNode(AlterFunctionStmt);
+
+	COPY_NODE_FIELD(func);
+	COPY_NODE_FIELD(actions);
+
+	return newnode;
+}
+
 static RemoveAggrStmt *
 _copyRemoveAggrStmt(RemoveAggrStmt *from)
 {
@@ -2882,6 +2893,9 @@ copyObject(void *from)
 		case T_FunctionParameter:
 			retval = _copyFunctionParameter(from);
 			break;
+		case T_AlterFunctionStmt:
+			retval = _copyAlterFunctionStmt(from);
+			break;
 		case T_RemoveAggrStmt:
 			retval = _copyRemoveAggrStmt(from);
 			break;
diff --git a/src/backend/nodes/equalfuncs.c b/src/backend/nodes/equalfuncs.c
index f80da7572b5..cbd99dab720 100644
--- a/src/backend/nodes/equalfuncs.c
+++ b/src/backend/nodes/equalfuncs.c
@@ -18,7 +18,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/nodes/equalfuncs.c,v 1.236 2005/03/10 23:21:21 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/nodes/equalfuncs.c,v 1.237 2005/03/14 00:19:36 neilc Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -954,6 +954,15 @@ _equalFunctionParameter(FunctionParameter *a, FunctionParameter *b)
 }
 
 static bool
+_equalAlterFunctionStmt(AlterFunctionStmt *a, AlterFunctionStmt *b)
+{
+	COMPARE_NODE_FIELD(func);
+	COMPARE_NODE_FIELD(actions);
+
+	return true;
+}
+
+static bool
 _equalRemoveAggrStmt(RemoveAggrStmt *a, RemoveAggrStmt *b)
 {
 	COMPARE_NODE_FIELD(aggname);
@@ -2014,6 +2023,9 @@ equal(void *a, void *b)
 		case T_FunctionParameter:
 			retval = _equalFunctionParameter(a, b);
 			break;
+		case T_AlterFunctionStmt:
+			retval = _equalAlterFunctionStmt(a, b);
+			break;
 		case T_RemoveAggrStmt:
 			retval = _equalRemoveAggrStmt(a, b);
 			break;
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index 69e70821970..a88262d4328 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -11,7 +11,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/parser/gram.y,v 2.483 2005/02/02 06:36:01 neilc Exp $
+ *	  $PostgreSQL: pgsql/src/backend/parser/gram.y,v 2.484 2005/03/14 00:19:36 neilc Exp $
  *
  * HISTORY
  *	  AUTHOR			DATE			MAJOR EVENT
@@ -142,7 +142,7 @@ static void doNegateFloat(Value *v);
 		DropUserStmt DropdbStmt DropTableSpaceStmt ExplainStmt FetchStmt
 		GrantStmt IndexStmt InsertStmt ListenStmt LoadStmt
 		LockStmt NotifyStmt ExplainableStmt PreparableStmt
-		CreateFunctionStmt ReindexStmt RemoveAggrStmt
+		CreateFunctionStmt AlterFunctionStmt ReindexStmt RemoveAggrStmt
 		RemoveFuncStmt RemoveOperStmt RenameStmt RevokeStmt
 		RuleActionStmt RuleActionStmtOrEmpty RuleStmt
 		SelectStmt TransactionStmt TruncateStmt
@@ -213,7 +213,7 @@ static void doNegateFloat(Value *v);
 %type <list>	stmtblock stmtmulti
 				OptTableElementList TableElementList OptInherit definition
 				opt_distinct opt_definition func_args
-				func_args_list func_as createfunc_opt_list
+				func_args_list func_as createfunc_opt_list alterfunc_opt_list
 				oper_argtypes RuleActionList RuleActionMulti
 				opt_column_list columnList opt_name_list
 				sort_clause opt_sort_clause sortby_list index_params
@@ -231,7 +231,7 @@ static void doNegateFloat(Value *v);
 
 %type <range>	into_clause OptTempTableName
 
-%type <defelt>	createfunc_opt_item
+%type <defelt>	createfunc_opt_item common_func_opt_item
 %type <fun_param> func_arg
 %type <typnam>	func_return func_type aggr_argtype
 
@@ -486,6 +486,7 @@ stmtmulti:	stmtmulti ';' stmt
 stmt :
 			AlterDatabaseSetStmt
 			| AlterDomainStmt
+			| AlterFunctionStmt
 			| AlterGroupStmt
 			| AlterOwnerStmt
 			| AlterSeqStmt
@@ -3371,14 +3372,21 @@ createfunc_opt_list:
 			| createfunc_opt_list createfunc_opt_item { $$ = lappend($1, $2); }
 	;
 
-createfunc_opt_item:
-			AS func_as
+/*
+ * Options common to both CREATE FUNCTION and ALTER FUNCTION
+ */
+common_func_opt_item:
+			CALLED ON NULL_P INPUT_P
 				{
-					$$ = makeDefElem("as", (Node *)$2);
+					$$ = makeDefElem("strict", (Node *)makeInteger(FALSE));
 				}
-			| LANGUAGE ColId_or_Sconst
+			| RETURNS NULL_P ON NULL_P INPUT_P
 				{
-					$$ = makeDefElem("language", (Node *)makeString($2));
+					$$ = makeDefElem("strict", (Node *)makeInteger(TRUE));
+				}
+			| STRICT_P
+				{
+					$$ = makeDefElem("strict", (Node *)makeInteger(TRUE));
 				}
 			| IMMUTABLE
 				{
@@ -3392,18 +3400,7 @@ createfunc_opt_item:
 				{
 					$$ = makeDefElem("volatility", (Node *)makeString("volatile"));
 				}
-			| CALLED ON NULL_P INPUT_P
-				{
-					$$ = makeDefElem("strict", (Node *)makeInteger(FALSE));
-				}
-			| RETURNS NULL_P ON NULL_P INPUT_P
-				{
-					$$ = makeDefElem("strict", (Node *)makeInteger(TRUE));
-				}
-			| STRICT_P
-				{
-					$$ = makeDefElem("strict", (Node *)makeInteger(TRUE));
-				}
+
 			| EXTERNAL SECURITY DEFINER
 				{
 					$$ = makeDefElem("security", (Node *)makeInteger(TRUE));
@@ -3422,6 +3419,21 @@ createfunc_opt_item:
 				}
 		;
 
+createfunc_opt_item:
+			AS func_as
+				{
+					$$ = makeDefElem("as", (Node *)$2);
+				}
+			| LANGUAGE ColId_or_Sconst
+				{
+					$$ = makeDefElem("language", (Node *)makeString($2));
+				}
+			| common_func_opt_item
+				{
+					$$ = $1;
+				}
+		;
+
 func_as:	Sconst						{ $$ = list_make1(makeString($1)); }
 			| Sconst ',' Sconst
 				{
@@ -3434,6 +3446,36 @@ opt_definition:
 			| /*EMPTY*/								{ $$ = NIL; }
 		;
 
+/*****************************************************************************
+ * ALTER FUNCTION
+ *
+ * RENAME and OWNER subcommands are already provided by the generic
+ * ALTER infrastructure, here we just specify alterations that can
+ * only be applied to functions.
+ *
+ *****************************************************************************/
+AlterFunctionStmt:
+			ALTER FUNCTION function_with_argtypes alterfunc_opt_list opt_restrict
+				{
+					AlterFunctionStmt *n = makeNode(AlterFunctionStmt);
+					n->func = (FuncWithArgs *) $3;
+					n->actions = $4;
+					$$ = (Node *) n;
+				}
+		;
+
+alterfunc_opt_list:
+			/* At least one option must be specified */
+			common_func_opt_item					{ $$ = list_make1($1); }
+			| alterfunc_opt_list common_func_opt_item { $$ = lappend($1, $2); }
+		;
+
+/* Ignored, merely for SQL compliance */
+opt_restrict:
+			RESTRICT
+			| /* EMPTY */
+		;
+
 
 /*****************************************************************************
  *
diff --git a/src/backend/tcop/utility.c b/src/backend/tcop/utility.c
index 006f904f72e..a3b946647ac 100644
--- a/src/backend/tcop/utility.c
+++ b/src/backend/tcop/utility.c
@@ -10,7 +10,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/tcop/utility.c,v 1.233 2005/01/27 03:18:10 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/tcop/utility.c,v 1.234 2005/03/14 00:19:36 neilc Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -277,6 +277,7 @@ check_xact_readonly(Node *parsetree)
 	{
 		case T_AlterDatabaseSetStmt:
 		case T_AlterDomainStmt:
+		case T_AlterFunctionStmt:
 		case T_AlterGroupStmt:
 		case T_AlterOwnerStmt:
 		case T_AlterSeqStmt:
@@ -711,6 +712,10 @@ ProcessUtility(Node *parsetree,
 			CreateFunction((CreateFunctionStmt *) parsetree);
 			break;
 
+		case T_AlterFunctionStmt: /* ALTER FUNCTION */
+			AlterFunction((AlterFunctionStmt *) parsetree);
+			break;
+
 		case T_IndexStmt:		/* CREATE INDEX */
 			{
 				IndexStmt  *stmt = (IndexStmt *) parsetree;
@@ -1394,10 +1399,15 @@ CreateCommandTag(Node *parsetree)
 					tag = "ALTER TABLE";
 			}
 			break;
+
 		case T_AlterDomainStmt:
 			tag = "ALTER DOMAIN";
 			break;
 
+		case T_AlterFunctionStmt:
+			tag = "ALTER FUNCTION";
+			break;
+
 		case T_GrantStmt:
 			{
 				GrantStmt  *stmt = (GrantStmt *) parsetree;
diff --git a/src/include/commands/defrem.h b/src/include/commands/defrem.h
index 30f576d7811..546e9f8dc0d 100644
--- a/src/include/commands/defrem.h
+++ b/src/include/commands/defrem.h
@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/commands/defrem.h,v 1.62 2004/12/31 22:03:28 pgsql Exp $
+ * $PostgreSQL: pgsql/src/include/commands/defrem.h,v 1.63 2005/03/14 00:19:37 neilc Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -49,6 +49,7 @@ extern void SetFunctionReturnType(Oid funcOid, Oid newRetType);
 extern void SetFunctionArgType(Oid funcOid, int argIndex, Oid newArgType);
 extern void RenameFunction(List *name, List *argtypes, const char *newname);
 extern void AlterFunctionOwner(List *name, List *argtypes, AclId newOwnerSysId);
+extern void AlterFunction(AlterFunctionStmt *stmt);
 extern void CreateCast(CreateCastStmt *stmt);
 extern void DropCast(DropCastStmt *stmt);
 extern void DropCastById(Oid castOid);
diff --git a/src/include/nodes/nodes.h b/src/include/nodes/nodes.h
index 291b1f281f2..5d70180a0c5 100644
--- a/src/include/nodes/nodes.h
+++ b/src/include/nodes/nodes.h
@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/nodes/nodes.h,v 1.163 2004/12/31 22:03:34 pgsql Exp $
+ * $PostgreSQL: pgsql/src/include/nodes/nodes.h,v 1.164 2005/03/14 00:19:37 neilc Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -223,6 +223,7 @@ typedef enum NodeTag
 	T_FetchStmt,
 	T_IndexStmt,
 	T_CreateFunctionStmt,
+	T_AlterFunctionStmt,
 	T_RemoveAggrStmt,
 	T_RemoveFuncStmt,
 	T_RemoveOperStmt,
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index cd3eb634d4a..8cf274b14ce 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/nodes/parsenodes.h,v 1.273 2005/03/10 23:21:24 tgl Exp $
+ * $PostgreSQL: pgsql/src/include/nodes/parsenodes.h,v 1.274 2005/03/14 00:19:37 neilc Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -1397,6 +1397,13 @@ typedef struct FunctionParameter
 	/* someday add IN/OUT/INOUT indicator here */
 } FunctionParameter;
 
+typedef struct AlterFunctionStmt
+{
+	NodeTag		type;
+	FuncWithArgs *func;			/* name and args of function */
+	List	   *actions;		/* list of DefElem */
+} AlterFunctionStmt;
+
 /* ----------------------
  *		Drop Aggregate Statement
  * ----------------------
diff --git a/src/test/regress/expected/alter_table.out b/src/test/regress/expected/alter_table.out
index fbb23a4b127..b9edbc649d4 100644
--- a/src/test/regress/expected/alter_table.out
+++ b/src/test/regress/expected/alter_table.out
@@ -1235,3 +1235,38 @@ select * from another;
 (3 rows)
 
 drop table another;
+--
+-- alter function
+--
+create function test_strict(text) returns text as
+    'select coalesce($1, ''got passed a null'');'
+    language sql returns null on null input;
+select test_strict(NULL);
+ test_strict 
+-------------
+ 
+(1 row)
+
+alter function test_strict(text) called on null input;
+select test_strict(NULL);
+    test_strict    
+-------------------
+ got passed a null
+(1 row)
+
+create function non_strict(text) returns text as
+    'select coalesce($1, ''got passed a null'');'
+    language sql called on null input;
+select non_strict(NULL);
+    non_strict     
+-------------------
+ got passed a null
+(1 row)
+
+alter function non_strict(text) returns null on null input;
+select non_strict(NULL);
+ non_strict 
+------------
+ 
+(1 row)
+
diff --git a/src/test/regress/sql/alter_table.sql b/src/test/regress/sql/alter_table.sql
index e6be119ff7d..445fabf7e09 100644
--- a/src/test/regress/sql/alter_table.sql
+++ b/src/test/regress/sql/alter_table.sql
@@ -975,3 +975,20 @@ alter table another
 select * from another;
 
 drop table another;
+
+--
+-- alter function
+--
+create function test_strict(text) returns text as
+    'select coalesce($1, ''got passed a null'');'
+    language sql returns null on null input;
+select test_strict(NULL);
+alter function test_strict(text) called on null input;
+select test_strict(NULL);
+
+create function non_strict(text) returns text as
+    'select coalesce($1, ''got passed a null'');'
+    language sql called on null input;
+select non_strict(NULL);
+alter function non_strict(text) returns null on null input;
+select non_strict(NULL);
\ No newline at end of file