This patch allows ALTER FUNCTION set change a function's strictness. In and of itself this isn't very useful, but it is defined in SQL2003, so it's probably worth implementing.

Notes:

- the optimizer considers strictness; for example, the optimizer will pre-evaluate calls to a strict function that is passed NULL (i.e. replacing the function call with a NULL). This means if you create a function, create a plan that calls the function, change the function's strictness, and then invoke the stored plan, the function's old strictness will still apply. Considering we have rather more serious problems involving out-of-date plans following DDL, I don't think this is a big deal, but I thought I'd mention it.

- SQL *requires* a "CASCADE" keyword following the ALTER command. I made it optional, but even optional it's a little ugly.

- I considered making it possible to change other attributes of a function (e.g. volatility and security definer), and the patch is implemented such that this should be easy to do. Does anyone think this is worth doing? (The same kinds of not-flushing-dependent-objects on ALTER issues apply as with strictness and saved plans.)

- SQL also specifies that the LANGUAGE clause of the function definition should be modifiable, but that strikes me as quite bizarre. The other things SQL defines for ALTER FUNCTION don't have equivalents in PG (<parameter style clause>, <SQL-data access indication>, <dynamic result sets characteristic>, and NAME <external routine name>).

Incidentally, is there a reason that DROP FUNCTION doesn't use the FuncWithArgs node? Given that the latter exists, ISTM we may as well use it where applicable.

-Neil
Index: doc/src/sgml/ref/alter_function.sgml
===================================================================
RCS file: /Users/neilc/local/cvs/pgsql/doc/src/sgml/ref/alter_function.sgml,v
retrieving revision 1.5
diff -c -r1.5 alter_function.sgml
*** doc/src/sgml/ref/alter_function.sgml	25 Jun 2004 21:55:50 -0000	1.5
--- doc/src/sgml/ref/alter_function.sgml	12 Mar 2005 13:42:28 -0000
***************
*** 20,27 ****
--- 20,34 ----
  
   <refsynopsisdiv>
  <synopsis>
+ ALTER FUNCTION <replaceable>name</replaceable> ( [ <replaceable class="parameter">type</replaceable> [, ...] ] ) <replaceable class="PARAMETER">action</replaceable> [, ... ] [ RESTRICT ]
  ALTER FUNCTION <replaceable>name</replaceable> ( [ <replaceable class="parameter">type</replaceable> [, ...] ] ) RENAME TO <replaceable>newname</replaceable>
  ALTER FUNCTION <replaceable>name</replaceable> ( [ <replaceable class="parameter">type</replaceable> [, ...] ] ) OWNER TO <replaceable>newowner</replaceable>
+ 
+ where <replaceable class="PARAMETER">action</replaceable> is one of:
+ 
+     CALLED ON NULL INPUT
+     RETURNS NULL ON NULL INPUT
+     STRICT
  </synopsis>
   </refsynopsisdiv>
    
***************
*** 69,79 ****
      <term><replaceable class="parameter">newowner</replaceable></term>
      <listitem>
       <para>
!       The new owner of the function.
!       To change the owner of a function, you must be a superuser.
!       Note that if the function is marked
!       <literal>SECURITY DEFINER</literal>,
!       it will subsequently execute as the new owner.
       </para>
      </listitem>
     </varlistentry>
--- 76,112 ----
      <term><replaceable class="parameter">newowner</replaceable></term>
      <listitem>
       <para>
!       The new owner of the function.  To change the owner of a
!       function, you must be a superuser.  Note that if the function is
!       marked <literal>SECURITY DEFINER</literal>, it will subsequently
!       execute as the new owner.
!      </para>
!     </listitem>
!    </varlistentry>
! 
!     <varlistentry>
!      <term><literal>CALLED ON NULL INPUT</literal></term>
!      <term><literal>RETURNS NULL ON NULL INPUT</literal></term>
!      <term><literal>STRICT</literal></term>
! 
!      <listitem>
!       <para>
!        <literal>CALLED ON NULL INPUT</literal> changes the function so
!        that it will be invoked when some or all of its arguments are
!        null. <literal>RETURNS NULL ON NULL INPUT</literal> or
!        <literal>STRICT</literal> changes the function so that it
!        always returns null if any of its arguments are null. See <xref
!        linkend="sql-createfunction"> for more information.
!       </para>
!      </listitem>
!    </varlistentry>
! 
!    <varlistentry>
!     <term><literal>RESTRICT</literal></term>
! 
!     <listitem>
!      <para>
!       Ignored for compatibility with the SQL standard.
       </para>
      </listitem>
     </varlistentry>
***************
*** 104,112 ****
    <title>Compatibility</title>
  
    <para>
!    There is an <command>ALTER FUNCTION</command> statement in the SQL
!    standard, but it does not provide the option to rename the
!    function or change the owner.
    </para>
   </refsect1>
  
--- 137,146 ----
    <title>Compatibility</title>
  
    <para>
!    This statement is partially compatible with the <command>ALTER
!    FUNCTION</command> statement in the SQL standard. The standard
!    allows more properties of a function to be modified, but does not
!    provide the ability to rename a function or changes its owner.
    </para>
   </refsect1>
  
Index: doc/src/sgml/ref/alter_index.sgml
===================================================================
RCS file: /Users/neilc/local/cvs/pgsql/doc/src/sgml/ref/alter_index.sgml,v
retrieving revision 1.4
diff -c -r1.4 alter_index.sgml
*** doc/src/sgml/ref/alter_index.sgml	24 Aug 2004 00:06:51 -0000	1.4
--- doc/src/sgml/ref/alter_index.sgml	12 Mar 2005 12:09:43 -0000
***************
*** 20,29 ****
  
   <refsynopsisdiv>
  <synopsis>
! ALTER INDEX <replaceable class="PARAMETER">name</replaceable> 
!     <replaceable class="PARAMETER">action</replaceable> [, ... ]
! ALTER INDEX <replaceable class="PARAMETER">name</replaceable>
!     RENAME TO <replaceable class="PARAMETER">new_name</replaceable>
  
  where <replaceable class="PARAMETER">action</replaceable> is one of:
  
--- 20,27 ----
  
   <refsynopsisdiv>
  <synopsis>
! ALTER INDEX <replaceable class="PARAMETER">name</replaceable> <replaceable class="PARAMETER">action</replaceable> [, ... ]
! ALTER INDEX <replaceable class="PARAMETER">name</replaceable> RENAME TO <replaceable class="PARAMETER">new_name</replaceable>
  
  where <replaceable class="PARAMETER">action</replaceable> is one of:
  
Index: src/backend/commands/functioncmds.c
===================================================================
RCS file: /Users/neilc/local/cvs/pgsql/src/backend/commands/functioncmds.c,v
retrieving revision 1.54
diff -c -r1.54 functioncmds.c
*** src/backend/commands/functioncmds.c	27 Jan 2005 23:23:55 -0000	1.54
--- src/backend/commands/functioncmds.c	12 Mar 2005 13:19:44 -0000
***************
*** 3,9 ****
   * functioncmds.c
   *
   *	  Routines for CREATE and DROP FUNCTION commands and CREATE and DROP
!  *		  CAST commands.
   *
   * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
   * Portions Copyright (c) 1994, Regents of the University of California
--- 3,9 ----
   * functioncmds.c
   *
   *	  Routines for CREATE and DROP FUNCTION commands and CREATE and DROP
!  *	  CAST commands.
   *
   * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
   * Portions Copyright (c) 1994, Regents of the University of California
***************
*** 805,811 ****
--- 805,877 ----
  	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;
+ 
+ 	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. Right now we only support changing
+ 	 * a function's strictness, so there's not much point refactoring
+ 	 * this to share code with CREATE FUNCTION. If the list of actions
+ 	 * grows, reconsider this...
+ 	 */
+ 	if (list_length(stmt->actions) != 1)
+ 		ereport(ERROR,
+ 				(errcode(ERRCODE_SYNTAX_ERROR),
+ 				 errmsg("conflicting or redundant options")));
+ 
+ 	foreach (l, stmt->actions)
+ 	{
+ 		DefElem *defel = (DefElem *) lfirst(l);
  
+ 		if (strcmp(defel->defname, "strict") == 0)
+ 			procForm->proisstrict = intVal(defel->arg);
+ 		else
+ 			elog(ERROR, "option \"%s\" not recognized", defel->defname);
+ 	}
+ 
+ 	/* 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
Index: src/backend/nodes/copyfuncs.c
===================================================================
RCS file: /Users/neilc/local/cvs/pgsql/src/backend/nodes/copyfuncs.c,v
retrieving revision 1.297
diff -c -r1.297 copyfuncs.c
*** src/backend/nodes/copyfuncs.c	10 Mar 2005 23:21:21 -0000	1.297
--- src/backend/nodes/copyfuncs.c	12 Mar 2005 09:42:10 -0000
***************
*** 1892,1897 ****
--- 1892,1908 ----
  	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)
  {
***************
*** 2882,2887 ****
--- 2893,2901 ----
  		case T_FunctionParameter:
  			retval = _copyFunctionParameter(from);
  			break;
+ 		case T_AlterFunctionStmt:
+ 			retval = _copyAlterFunctionStmt(from);
+ 			break;
  		case T_RemoveAggrStmt:
  			retval = _copyRemoveAggrStmt(from);
  			break;
Index: src/backend/nodes/equalfuncs.c
===================================================================
RCS file: /Users/neilc/local/cvs/pgsql/src/backend/nodes/equalfuncs.c,v
retrieving revision 1.236
diff -c -r1.236 equalfuncs.c
*** src/backend/nodes/equalfuncs.c	10 Mar 2005 23:21:21 -0000	1.236
--- src/backend/nodes/equalfuncs.c	12 Mar 2005 09:39:34 -0000
***************
*** 954,959 ****
--- 954,968 ----
  }
  
  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);
***************
*** 2014,2019 ****
--- 2023,2031 ----
  		case T_FunctionParameter:
  			retval = _equalFunctionParameter(a, b);
  			break;
+ 		case T_AlterFunctionStmt:
+ 			retval = _equalAlterFunctionStmt(a, b);
+ 			break;
  		case T_RemoveAggrStmt:
  			retval = _equalRemoveAggrStmt(a, b);
  			break;
Index: src/backend/parser/gram.y
===================================================================
RCS file: /Users/neilc/local/cvs/pgsql/src/backend/parser/gram.y,v
retrieving revision 2.483
diff -c -r2.483 gram.y
*** src/backend/parser/gram.y	2 Feb 2005 06:36:01 -0000	2.483
--- src/backend/parser/gram.y	12 Mar 2005 10:44:21 -0000
***************
*** 142,148 ****
  		DropUserStmt DropdbStmt DropTableSpaceStmt ExplainStmt FetchStmt
  		GrantStmt IndexStmt InsertStmt ListenStmt LoadStmt
  		LockStmt NotifyStmt ExplainableStmt PreparableStmt
! 		CreateFunctionStmt ReindexStmt RemoveAggrStmt
  		RemoveFuncStmt RemoveOperStmt RenameStmt RevokeStmt
  		RuleActionStmt RuleActionStmtOrEmpty RuleStmt
  		SelectStmt TransactionStmt TruncateStmt
--- 142,148 ----
  		DropUserStmt DropdbStmt DropTableSpaceStmt ExplainStmt FetchStmt
  		GrantStmt IndexStmt InsertStmt ListenStmt LoadStmt
  		LockStmt NotifyStmt ExplainableStmt PreparableStmt
! 		CreateFunctionStmt AlterFunctionStmt ReindexStmt RemoveAggrStmt
  		RemoveFuncStmt RemoveOperStmt RenameStmt RevokeStmt
  		RuleActionStmt RuleActionStmtOrEmpty RuleStmt
  		SelectStmt TransactionStmt TruncateStmt
***************
*** 213,219 ****
  %type <list>	stmtblock stmtmulti
  				OptTableElementList TableElementList OptInherit definition
  				opt_distinct opt_definition func_args
! 				func_args_list func_as createfunc_opt_list
  				oper_argtypes RuleActionList RuleActionMulti
  				opt_column_list columnList opt_name_list
  				sort_clause opt_sort_clause sortby_list index_params
--- 213,219 ----
  %type <list>	stmtblock stmtmulti
  				OptTableElementList TableElementList OptInherit definition
  				opt_distinct opt_definition func_args
! 				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
***************
*** 231,237 ****
  
  %type <range>	into_clause OptTempTableName
  
! %type <defelt>	createfunc_opt_item
  %type <fun_param> func_arg
  %type <typnam>	func_return func_type aggr_argtype
  
--- 231,237 ----
  
  %type <range>	into_clause OptTempTableName
  
! %type <defelt>	createfunc_opt_item common_func_opt_item
  %type <fun_param> func_arg
  %type <typnam>	func_return func_type aggr_argtype
  
***************
*** 486,491 ****
--- 486,492 ----
  stmt :
  			AlterDatabaseSetStmt
  			| AlterDomainStmt
+ 			| AlterFunctionStmt
  			| AlterGroupStmt
  			| AlterOwnerStmt
  			| AlterSeqStmt
***************
*** 3371,3376 ****
--- 3372,3395 ----
  			| createfunc_opt_list createfunc_opt_item { $$ = lappend($1, $2); }
  	;
  
+ /*
+  * Options common to both CREATE FUNCTION and ALTER FUNCTION
+  */
+ common_func_opt_item:
+ 			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
+ 				{
+ 					$$ = makeDefElem("strict", (Node *)makeInteger(TRUE));
+ 				}
+ 		;
+ 
  createfunc_opt_item:
  			AS func_as
  				{
***************
*** 3392,3409 ****
  				{
  					$$ = 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));
--- 3411,3417 ----
  				{
  					$$ = makeDefElem("volatility", (Node *)makeString("volatile"));
  				}
! 
  			| EXTERNAL SECURITY DEFINER
  				{
  					$$ = makeDefElem("security", (Node *)makeInteger(TRUE));
***************
*** 3420,3425 ****
--- 3428,3437 ----
  				{
  					$$ = makeDefElem("security", (Node *)makeInteger(FALSE));
  				}
+ 			| common_func_opt_item
+ 				{
+ 					$$ = $1;
+ 				}
  		;
  
  func_as:	Sconst						{ $$ = list_make1(makeString($1)); }
***************
*** 3434,3439 ****
--- 3446,3481 ----
  			| /*EMPTY*/								{ $$ = NIL; }
  		;
  
+ /*****************************************************************************
+  * ALTER FUNCTION
+  *
+  * RENAME and OWNER subcommands are already provided by the generic
+  * ALTER infrastructure, so 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 */
+ 		;
+ 
  
  /*****************************************************************************
   *
Index: src/backend/tcop/utility.c
===================================================================
RCS file: /Users/neilc/local/cvs/pgsql/src/backend/tcop/utility.c,v
retrieving revision 1.233
diff -c -r1.233 utility.c
*** src/backend/tcop/utility.c	27 Jan 2005 03:18:10 -0000	1.233
--- src/backend/tcop/utility.c	12 Mar 2005 12:52:18 -0000
***************
*** 277,282 ****
--- 277,283 ----
  	{
  		case T_AlterDatabaseSetStmt:
  		case T_AlterDomainStmt:
+ 		case T_AlterFunctionStmt:
  		case T_AlterGroupStmt:
  		case T_AlterOwnerStmt:
  		case T_AlterSeqStmt:
***************
*** 711,716 ****
--- 712,721 ----
  			CreateFunction((CreateFunctionStmt *) parsetree);
  			break;
  
+ 		case T_AlterFunctionStmt: /* ALTER FUNCTION */
+ 			AlterFunction((AlterFunctionStmt *) parsetree);
+ 			break;
+ 
  		case T_IndexStmt:		/* CREATE INDEX */
  			{
  				IndexStmt  *stmt = (IndexStmt *) parsetree;
***************
*** 1394,1403 ****
--- 1399,1413 ----
  					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;
Index: src/include/commands/defrem.h
===================================================================
RCS file: /Users/neilc/local/cvs/pgsql/src/include/commands/defrem.h,v
retrieving revision 1.62
diff -c -r1.62 defrem.h
*** src/include/commands/defrem.h	31 Dec 2004 22:03:28 -0000	1.62
--- src/include/commands/defrem.h	12 Mar 2005 10:42:45 -0000
***************
*** 49,54 ****
--- 49,55 ----
  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);
Index: src/include/nodes/nodes.h
===================================================================
RCS file: /Users/neilc/local/cvs/pgsql/src/include/nodes/nodes.h,v
retrieving revision 1.163
diff -c -r1.163 nodes.h
*** src/include/nodes/nodes.h	31 Dec 2004 22:03:34 -0000	1.163
--- src/include/nodes/nodes.h	12 Mar 2005 09:37:33 -0000
***************
*** 223,228 ****
--- 223,229 ----
  	T_FetchStmt,
  	T_IndexStmt,
  	T_CreateFunctionStmt,
+ 	T_AlterFunctionStmt,
  	T_RemoveAggrStmt,
  	T_RemoveFuncStmt,
  	T_RemoveOperStmt,
Index: src/include/nodes/parsenodes.h
===================================================================
RCS file: /Users/neilc/local/cvs/pgsql/src/include/nodes/parsenodes.h,v
retrieving revision 1.273
diff -c -r1.273 parsenodes.h
*** src/include/nodes/parsenodes.h	10 Mar 2005 23:21:24 -0000	1.273
--- src/include/nodes/parsenodes.h	12 Mar 2005 09:37:00 -0000
***************
*** 1397,1402 ****
--- 1397,1409 ----
  	/* 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
   * ----------------------
Index: src/test/regress/expected/alter_table.out
===================================================================
RCS file: /Users/neilc/local/cvs/pgsql/src/test/regress/expected/alter_table.out,v
retrieving revision 1.86
diff -c -r1.86 alter_table.out
*** src/test/regress/expected/alter_table.out	22 Jan 2005 05:12:23 -0000	1.86
--- src/test/regress/expected/alter_table.out	12 Mar 2005 12:45:28 -0000
***************
*** 1235,1237 ****
--- 1235,1272 ----
  (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)
+ 
Index: src/test/regress/sql/alter_table.sql
===================================================================
RCS file: /Users/neilc/local/cvs/pgsql/src/test/regress/sql/alter_table.sql,v
retrieving revision 1.48
diff -c -r1.48 alter_table.sql
*** src/test/regress/sql/alter_table.sql	22 Jan 2005 05:12:33 -0000	1.48
--- src/test/regress/sql/alter_table.sql	12 Mar 2005 12:32:09 -0000
***************
*** 975,977 ****
--- 975,994 ----
  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
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