Make DROP FUNCTION hint more informative.

If you decide you want to take the hint, this gives you something you
can paste right back to the server.

Dean Rasheed

src/backend/catalog/pg_proc.c

@@ -404,7 +404,8 @@ ProcedureCreate(const char *procedureName,
 			ereport(ERROR,
 					(errcode(ERRCODE_INVALID_FUNCTION_DEFINITION),
 					 errmsg("cannot change return type of existing function"),
-					 errhint("Use DROP FUNCTION first.")));
+					 errhint("Use DROP FUNCTION %s first.",
+                             format_procedure(HeapTupleGetOid(oldtup)))));
 
 		/*
 		 * If it returns RECORD, check for possible change of record type
@@ -427,7 +428,8 @@ ProcedureCreate(const char *procedureName,
 						(errcode(ERRCODE_INVALID_FUNCTION_DEFINITION),
 					errmsg("cannot change return type of existing function"),
 				errdetail("Row type defined by OUT parameters is different."),
-						 errhint("Use DROP FUNCTION first.")));
+						 errhint("Use DROP FUNCTION %s first.",
+                                 format_procedure(HeapTupleGetOid(oldtup)))));
 		}
 
 		/*
@@ -469,7 +471,8 @@ ProcedureCreate(const char *procedureName,
 							(errcode(ERRCODE_INVALID_FUNCTION_DEFINITION),
 					   errmsg("cannot change name of input parameter \"%s\"",
 							  old_arg_names[j]),
-							 errhint("Use DROP FUNCTION first.")));
+							 errhint("Use DROP FUNCTION %s first.",
+                                     format_procedure(HeapTupleGetOid(oldtup)))));
 			}
 		}
 
@@ -492,7 +495,8 @@ ProcedureCreate(const char *procedureName,
 				ereport(ERROR,
 						(errcode(ERRCODE_INVALID_FUNCTION_DEFINITION),
 						 errmsg("cannot remove parameter defaults from existing function"),
-						 errhint("Use DROP FUNCTION first.")));
+						 errhint("Use DROP FUNCTION %s first.",
+                                 format_procedure(HeapTupleGetOid(oldtup)))));
 
 			proargdefaults = SysCacheGetAttr(PROCNAMEARGSNSP, oldtup,
 											 Anum_pg_proc_proargdefaults,
@@ -518,7 +522,8 @@ ProcedureCreate(const char *procedureName,
 					ereport(ERROR,
 							(errcode(ERRCODE_INVALID_FUNCTION_DEFINITION),
 							 errmsg("cannot change data type of existing parameter default value"),
-							 errhint("Use DROP FUNCTION first.")));
+							 errhint("Use DROP FUNCTION %s first.",
+                                     format_procedure(HeapTupleGetOid(oldtup)))));
 				newlc = lnext(newlc);
 			}
 		}

src/test/regress/expected/polymorphism.out

@@ -1026,7 +1026,7 @@ select dfunc(10,20);
 create or replace function dfunc(a variadic int[]) returns int as
 $$ select array_upper($1, 1) $$ language sql;
 ERROR:  cannot remove parameter defaults from existing function
-HINT:  Use DROP FUNCTION first.
+HINT:  Use DROP FUNCTION dfunc(integer[]) first.
 \df dfunc
                                       List of functions
  Schema | Name  | Result data type |               Argument data types               |  Type  
@@ -1239,13 +1239,13 @@ returns record as $$
   select $1, $2;
 $$ language sql;
 ERROR:  cannot change name of input parameter "c"
-HINT:  Use DROP FUNCTION first.
+HINT:  Use DROP FUNCTION dfunc(character varying,numeric) first.
 create or replace function dfunc(a varchar = 'def a', out _a varchar, numeric = NULL, out _c numeric)
 returns record as $$
   select $1, $2;
 $$ language sql;
 ERROR:  cannot change name of input parameter "c"
-HINT:  Use DROP FUNCTION first.
+HINT:  Use DROP FUNCTION dfunc(character varying,numeric) first.
 drop function dfunc(varchar, numeric);
 --fail, named parameters are not unique
 create function testfoo(a int, a int) returns int as $$ select 1;$$ language sql;

src/test/regress/expected/rangefuncs.out

@@ -439,7 +439,7 @@ CREATE OR REPLACE FUNCTION foo(in f1 int, out f2 int, out f3 text)
 RETURNS record
 AS 'select $1+1' LANGUAGE sql;
 ERROR:  cannot change return type of existing function
-HINT:  Use DROP FUNCTION first.
+HINT:  Use DROP FUNCTION foo(integer) first.
 CREATE OR REPLACE FUNCTION foor(in f1 int, out f2 int, out text)
 AS $$select $1-1, $1::text || 'z'$$ LANGUAGE sql;
 SELECT f1, foor(f1) FROM int4_tbl;
@@ -521,7 +521,7 @@ SELECT * FROM dup('xyz'::text);
 CREATE OR REPLACE FUNCTION dup (inout f2 anyelement, out f3 anyarray)
 AS 'select $1, array[$1,$1]' LANGUAGE sql;
 ERROR:  cannot change name of input parameter "f1"
-HINT:  Use DROP FUNCTION first.
+HINT:  Use DROP FUNCTION dup(anyelement) first.
 DROP FUNCTION dup(anyelement);
 -- equivalent behavior, though different name exposed for input arg
 CREATE OR REPLACE FUNCTION dup (inout f2 anyelement, out f3 anyarray)