Allow referring to functions without arguments when unique

petere · petere · commit aefeb68741fb · 2017-03-14T23:55:19.000-04:00
In DDL commands referring to an existing function, allow omitting the
argument list if the function name is unique in its schema, per SQL
standard.

This uses the same logic that the regproc type uses for finding
functions by name only.

Reviewed-by: Michael Paquier &lt;michael.paquier@gmail.com&gt;
diff --git a/doc/src/sgml/ref/alter_extension.sgml b/doc/src/sgml/ref/alter_extension.sgml
@@ -39,7 +39,7 @@ ALTER EXTENSION <replaceable class="PARAMETER">name</replaceable> DROP <replacea
   EVENT TRIGGER <replaceable class="PARAMETER">object_name</replaceable> |
   FOREIGN DATA WRAPPER <replaceable class="PARAMETER">object_name</replaceable> |
   FOREIGN TABLE <replaceable class="PARAMETER">object_name</replaceable> |
-  FUNCTION <replaceable class="PARAMETER">function_name</replaceable> ( [ [ <replaceable class="parameter">argmode</replaceable> ] [ <replaceable class="parameter">argname</replaceable> ] <replaceable class="parameter">argtype</replaceable> [, ...] ] ) |
+  FUNCTION <replaceable class="PARAMETER">function_name</replaceable> [ ( [ [ <replaceable class="parameter">argmode</replaceable> ] [ <replaceable class="parameter">argname</replaceable> ] <replaceable class="parameter">argtype</replaceable> [, ...] ] ) ] |
   MATERIALIZED VIEW <replaceable class="PARAMETER">object_name</replaceable> |
   OPERATOR <replaceable class="PARAMETER">operator_name</replaceable> (<replaceable class="PARAMETER">left_type</replaceable>, <replaceable class="PARAMETER">right_type</replaceable>) |
   OPERATOR CLASS <replaceable class="PARAMETER">object_name</replaceable> USING <replaceable class="parameter">index_method</replaceable> |
diff --git a/doc/src/sgml/ref/alter_function.sgml b/doc/src/sgml/ref/alter_function.sgml
@@ -21,15 +21,15 @@ PostgreSQL documentation
 
  <refsynopsisdiv>
 <synopsis>
-ALTER FUNCTION <replaceable>name</replaceable> ( [ [ <replaceable class="parameter">argmode</replaceable> ] [ <replaceable class="parameter">argname</replaceable> ] <replaceable class="parameter">argtype</replaceable> [, ...] ] )
+ALTER FUNCTION <replaceable>name</replaceable> [ ( [ [ <replaceable class="parameter">argmode</replaceable> ] [ <replaceable class="parameter">argname</replaceable> ] <replaceable class="parameter">argtype</replaceable> [, ...] ] ) ]
     <replaceable class="PARAMETER">action</replaceable> [ ... ] [ RESTRICT ]
-ALTER FUNCTION <replaceable>name</replaceable> ( [ [ <replaceable class="parameter">argmode</replaceable> ] [ <replaceable class="parameter">argname</replaceable> ] <replaceable class="parameter">argtype</replaceable> [, ...] ] )
+ALTER FUNCTION <replaceable>name</replaceable> [ ( [ [ <replaceable class="parameter">argmode</replaceable> ] [ <replaceable class="parameter">argname</replaceable> ] <replaceable class="parameter">argtype</replaceable> [, ...] ] ) ]
     RENAME TO <replaceable>new_name</replaceable>
-ALTER FUNCTION <replaceable>name</replaceable> ( [ [ <replaceable class="parameter">argmode</replaceable> ] [ <replaceable class="parameter">argname</replaceable> ] <replaceable class="parameter">argtype</replaceable> [, ...] ] )
+ALTER FUNCTION <replaceable>name</replaceable> [ ( [ [ <replaceable class="parameter">argmode</replaceable> ] [ <replaceable class="parameter">argname</replaceable> ] <replaceable class="parameter">argtype</replaceable> [, ...] ] ) ]
     OWNER TO { <replaceable>new_owner</replaceable> | CURRENT_USER | SESSION_USER }
-ALTER FUNCTION <replaceable>name</replaceable> ( [ [ <replaceable class="parameter">argmode</replaceable> ] [ <replaceable class="parameter">argname</replaceable> ] <replaceable class="parameter">argtype</replaceable> [, ...] ] )
+ALTER FUNCTION <replaceable>name</replaceable> [ ( [ [ <replaceable class="parameter">argmode</replaceable> ] [ <replaceable class="parameter">argname</replaceable> ] <replaceable class="parameter">argtype</replaceable> [, ...] ] ) ]
     SET SCHEMA <replaceable>new_schema</replaceable>
-ALTER FUNCTION <replaceable>name</replaceable> ( [ [ <replaceable class="parameter">argmode</replaceable> ] [ <replaceable class="parameter">argname</replaceable> ] <replaceable class="parameter">argtype</replaceable> [, ...] ] )
+ALTER FUNCTION <replaceable>name</replaceable> [ ( [ [ <replaceable class="parameter">argmode</replaceable> ] [ <replaceable class="parameter">argname</replaceable> ] <replaceable class="parameter">argtype</replaceable> [, ...] ] ) ]
     DEPENDS ON EXTENSION <replaceable>extension_name</replaceable>
 
 <phrase>where <replaceable class="PARAMETER">action</replaceable> is one of:</phrase>
@@ -75,7 +75,8 @@ ALTER FUNCTION <replaceable>name</replaceable> ( [ [ <replaceable class="paramet
     <term><replaceable class="parameter">name</replaceable></term>
     <listitem>
      <para>
-      The name (optionally schema-qualified) of an existing function.
+      The name (optionally schema-qualified) of an existing function.  If no
+      argument list is specified, the name must be unique in its schema.
      </para>
     </listitem>
    </varlistentry>
diff --git a/doc/src/sgml/ref/alter_opfamily.sgml b/doc/src/sgml/ref/alter_opfamily.sgml
@@ -25,7 +25,7 @@ ALTER OPERATOR FAMILY <replaceable>name</replaceable> USING <replaceable class="
   {  OPERATOR <replaceable class="parameter">strategy_number</replaceable> <replaceable class="parameter">operator_name</replaceable> ( <replaceable class="parameter">op_type</replaceable>, <replaceable class="parameter">op_type</replaceable> )
               [ FOR SEARCH | FOR ORDER BY <replaceable class="parameter">sort_family_name</replaceable> ]
    | FUNCTION <replaceable class="parameter">support_number</replaceable> [ ( <replaceable class="parameter">op_type</replaceable> [ , <replaceable class="parameter">op_type</replaceable> ] ) ]
-              <replaceable class="parameter">function_name</replaceable> ( <replaceable class="parameter">argument_type</replaceable> [, ...] )
+              <replaceable class="parameter">function_name</replaceable> [ ( <replaceable class="parameter">argument_type</replaceable> [, ...] ) ]
   } [, ... ]
 
 ALTER OPERATOR FAMILY <replaceable>name</replaceable> USING <replaceable class="parameter">index_method</replaceable> DROP
@@ -195,8 +195,9 @@ ALTER OPERATOR FAMILY <replaceable>name</replaceable> USING <replaceable class="
     <term><replaceable class="parameter">function_name</replaceable></term>
     <listitem>
      <para>
-      The name (optionally schema-qualified) of a function that is an
-      index method support procedure for the operator family.
+      The name (optionally schema-qualified) of a function that is an index
+      method support procedure for the operator family.  If no argument list
+      is specified, the name must be unique in its schema.
      </para>
     </listitem>
    </varlistentry>
diff --git a/doc/src/sgml/ref/comment.sgml b/doc/src/sgml/ref/comment.sgml
@@ -37,7 +37,7 @@ COMMENT ON
   EVENT TRIGGER <replaceable class="PARAMETER">object_name</replaceable> |
   FOREIGN DATA WRAPPER <replaceable class="PARAMETER">object_name</replaceable> |
   FOREIGN TABLE <replaceable class="PARAMETER">object_name</replaceable> |
-  FUNCTION <replaceable class="PARAMETER">function_name</replaceable> ( [ [ <replaceable class="parameter">argmode</replaceable> ] [ <replaceable class="parameter">argname</replaceable> ] <replaceable class="parameter">argtype</replaceable> [, ...] ] ) |
+  FUNCTION <replaceable class="PARAMETER">function_name</replaceable> [ ( [ [ <replaceable class="parameter">argmode</replaceable> ] [ <replaceable class="parameter">argname</replaceable> ] <replaceable class="parameter">argtype</replaceable> [, ...] ] ) ] |
   INDEX <replaceable class="PARAMETER">object_name</replaceable> |
   LARGE OBJECT <replaceable class="PARAMETER">large_object_oid</replaceable> |
   MATERIALIZED VIEW <replaceable class="PARAMETER">object_name</replaceable> |
diff --git a/doc/src/sgml/ref/create_cast.sgml b/doc/src/sgml/ref/create_cast.sgml
@@ -19,7 +19,7 @@
  <refsynopsisdiv>
 <synopsis>
 CREATE CAST (<replaceable>source_type</replaceable> AS <replaceable>target_type</replaceable>)
-    WITH FUNCTION <replaceable>function_name</replaceable> (<replaceable>argument_type</replaceable> [, ...])
+    WITH FUNCTION <replaceable>function_name</replaceable> [ (<replaceable>argument_type</replaceable> [, ...]) ]
     [ AS ASSIGNMENT | AS IMPLICIT ]
 
 CREATE CAST (<replaceable>source_type</replaceable> AS <replaceable>target_type</replaceable>)
@@ -192,14 +192,16 @@ SELECT CAST ( 2 AS numeric ) + 4.0;
     </varlistentry>
 
     <varlistentry>
-     <term><replaceable>function_name</replaceable>(<replaceable>argument_type</replaceable> [, ...])</term>
+     <term><literal><replaceable>function_name</replaceable>[(<replaceable>argument_type</replaceable> [, ...])]</literal></term>
 
      <listitem>
       <para>
        The function used to perform the cast.  The function name can
        be schema-qualified.  If it is not, the function will be looked
        up in the schema search path.  The function's result data type must
        match the target type of the cast.   Its arguments are discussed below.
+       If no argument list is specified, the function name must be unique in
+       its schema.
       </para>
      </listitem>
     </varlistentry>
diff --git a/doc/src/sgml/ref/create_transform.sgml b/doc/src/sgml/ref/create_transform.sgml
@@ -19,8 +19,8 @@
  <refsynopsisdiv>
 <synopsis>
 CREATE [ OR REPLACE ] TRANSFORM FOR <replaceable>type_name</replaceable> LANGUAGE <replaceable>lang_name</replaceable> (
-    FROM SQL WITH FUNCTION <replaceable>from_sql_function_name</replaceable> (<replaceable>argument_type</replaceable> [, ...]),
-    TO SQL WITH FUNCTION <replaceable>to_sql_function_name</replaceable> (<replaceable>argument_type</replaceable> [, ...])
+    FROM SQL WITH FUNCTION <replaceable>from_sql_function_name</replaceable> [ (<replaceable>argument_type</replaceable> [, ...]) ],
+    TO SQL WITH FUNCTION <replaceable>to_sql_function_name</replaceable> [ (<replaceable>argument_type</replaceable> [, ...]) ]
 );
 </synopsis>
  </refsynopsisdiv>
@@ -104,7 +104,7 @@ CREATE [ OR REPLACE ] TRANSFORM FOR <replaceable>type_name</replaceable> LANGUAG
     </varlistentry>
 
     <varlistentry>
-     <term><replaceable>from_sql_function_name</replaceable>(<replaceable>argument_type</replaceable> [, ...])</term>
+     <term><literal><replaceable>from_sql_function_name</replaceable>[(<replaceable>argument_type</replaceable> [, ...])]</literal></term>
 
      <listitem>
       <para>
@@ -116,12 +116,14 @@ CREATE [ OR REPLACE ] TRANSFORM FOR <replaceable>type_name</replaceable> LANGUAG
        SQL-level function returning <type>internal</type> without at
        least one argument of type <type>internal</type>.)  The actual return
        value will be something specific to the language implementation.
+       If no argument list is specified, the function name must be unique in
+       its schema.
       </para>
      </listitem>
     </varlistentry>
 
     <varlistentry>
-     <term><replaceable>to_sql_function_name</replaceable>(<replaceable>argument_type</replaceable> [, ...])</term>
+     <term><literal><replaceable>to_sql_function_name</replaceable>[(<replaceable>argument_type</replaceable> [, ...])]</literal></term>
 
      <listitem>
       <para>
@@ -130,6 +132,8 @@ CREATE [ OR REPLACE ] TRANSFORM FOR <replaceable>type_name</replaceable> LANGUAG
        <type>internal</type> and return the type that is the type for the
        transform.  The actual argument value will be something specific to the
        language implementation.
+       If no argument list is specified, the function name must be unique in
+       its schema.
       </para>
      </listitem>
     </varlistentry>
diff --git a/doc/src/sgml/ref/drop_function.sgml b/doc/src/sgml/ref/drop_function.sgml
@@ -21,7 +21,7 @@ PostgreSQL documentation
 
  <refsynopsisdiv>
 <synopsis>
-DROP FUNCTION [ IF EXISTS ] <replaceable class="parameter">name</replaceable> ( [ [ <replaceable class="parameter">argmode</replaceable> ] [ <replaceable class="parameter">argname</replaceable> ] <replaceable class="parameter">argtype</replaceable> [, ...] ] ) [, ...]
+DROP FUNCTION [ IF EXISTS ] <replaceable class="parameter">name</replaceable> [ ( [ [ <replaceable class="parameter">argmode</replaceable> ] [ <replaceable class="parameter">argname</replaceable> ] <replaceable class="parameter">argtype</replaceable> [, ...] ] ) ] [, ...]
     [ CASCADE | RESTRICT ]
 </synopsis>
  </refsynopsisdiv>
@@ -56,7 +56,8 @@ DROP FUNCTION [ IF EXISTS ] <replaceable class="parameter">name</replaceable> (
     <term><replaceable class="parameter">name</replaceable></term>
     <listitem>
      <para>
-      The name (optionally schema-qualified) of an existing function.
+      The name (optionally schema-qualified) of an existing function.  If no
+      argument list is specified, the name must be unique in its schema.
      </para>
     </listitem>
    </varlistentry>
@@ -141,14 +142,40 @@ DROP FUNCTION sqrt(integer);
 <programlisting>
 DROP FUNCTION sqrt(integer), sqrt(bigint);
 </programlisting></para>
+
+  <para>
+   If the function name is unique in its schema, it can be referred to without
+   an argument list:
+<programlisting>
+DROP FUNCTION update_employee_salaries;
+</programlisting>
+   Note that this is different from
+<programlisting>
+DROP FUNCTION update_employee_salaries();
+</programlisting>
+   which refers to a function with zero arguments, whereas the first variant
+   can refer to a function with any number of arguments, including zero, as
+   long as the name is unique.
+  </para>
  </refsect1>
 
  <refsect1 id="SQL-DROPFUNCTION-compatibility">
   <title>Compatibility</title>
 
   <para>
-   A <command>DROP FUNCTION</command> statement is defined in the SQL
-   standard, but it is not compatible with this command.
+   This command conforms to the SQL standard, with
+   these <productname>PostgreSQL</productname> extensions:
+   <itemizedlist>
+    <listitem>
+     <para>The standard only allows one function to be dropped per command.</para>
+    </listitem>
+    <listitem>
+     <para>The <literal>IF EXISTS</literal> option</para>
+    </listitem>
+    <listitem>
+     <para>The ability to specify argument modes and names</para>
+    </listitem>
+   </itemizedlist>
   </para>
  </refsect1>
 
diff --git a/doc/src/sgml/ref/grant.sgml b/doc/src/sgml/ref/grant.sgml
@@ -55,7 +55,7 @@ GRANT { USAGE | ALL [ PRIVILEGES ] }
     TO <replaceable class="PARAMETER">role_specification</replaceable> [, ...] [ WITH GRANT OPTION ]
 
 GRANT { EXECUTE | ALL [ PRIVILEGES ] }
-    ON { FUNCTION <replaceable>function_name</replaceable> ( [ [ <replaceable class="parameter">argmode</replaceable> ] [ <replaceable class="parameter">arg_name</replaceable> ] <replaceable class="parameter">arg_type</replaceable> [, ...] ] ) [, ...]
+    ON { FUNCTION <replaceable>function_name</replaceable> [ ( [ [ <replaceable class="parameter">argmode</replaceable> ] [ <replaceable class="parameter">arg_name</replaceable> ] <replaceable class="parameter">arg_type</replaceable> [, ...] ] ) ] [, ...]
          | ALL FUNCTIONS IN SCHEMA <replaceable class="PARAMETER">schema_name</replaceable> [, ...] }
     TO <replaceable class="PARAMETER">role_specification</replaceable> [, ...] [ WITH GRANT OPTION ]
 
diff --git a/doc/src/sgml/ref/revoke.sgml b/doc/src/sgml/ref/revoke.sgml
@@ -70,7 +70,7 @@ REVOKE [ GRANT OPTION FOR ]
 
 REVOKE [ GRANT OPTION FOR ]
     { EXECUTE | ALL [ PRIVILEGES ] }
-    ON { FUNCTION <replaceable>function_name</replaceable> ( [ [ <replaceable class="parameter">argmode</replaceable> ] [ <replaceable class="parameter">arg_name</replaceable> ] <replaceable class="parameter">arg_type</replaceable> [, ...] ] ) [, ...]
+    ON { FUNCTION <replaceable>function_name</replaceable> [ ( [ [ <replaceable class="parameter">argmode</replaceable> ] [ <replaceable class="parameter">arg_name</replaceable> ] <replaceable class="parameter">arg_type</replaceable> [, ...] ] ) ] [, ...]
          | ALL FUNCTIONS IN SCHEMA <replaceable>schema_name</replaceable> [, ...] }
     FROM { [ GROUP ] <replaceable class="PARAMETER">role_name</replaceable> | PUBLIC } [, ...]
     [ CASCADE | RESTRICT ]
diff --git a/doc/src/sgml/ref/security_label.sgml b/doc/src/sgml/ref/security_label.sgml
@@ -30,7 +30,7 @@ SECURITY LABEL [ FOR <replaceable class="PARAMETER">provider</replaceable> ] ON
   DOMAIN <replaceable class="PARAMETER">object_name</replaceable> |
   EVENT TRIGGER <replaceable class="PARAMETER">object_name</replaceable> |
   FOREIGN TABLE <replaceable class="PARAMETER">object_name</replaceable>
-  FUNCTION <replaceable class="PARAMETER">function_name</replaceable> ( [ [ <replaceable class="parameter">argmode</replaceable> ] [ <replaceable class="parameter">argname</replaceable> ] <replaceable class="parameter">argtype</replaceable> [, ...] ] ) |
+  FUNCTION <replaceable class="PARAMETER">function_name</replaceable> [ ( [ [ <replaceable class="parameter">argmode</replaceable> ] [ <replaceable class="parameter">argname</replaceable> ] <replaceable class="parameter">argtype</replaceable> [, ...] ] ) ] |
   LARGE OBJECT <replaceable class="PARAMETER">large_object_oid</replaceable> |
   MATERIALIZED VIEW <replaceable class="PARAMETER">object_name</replaceable> |
   [ PROCEDURAL ] LANGUAGE <replaceable class="PARAMETER">object_name</replaceable> |
diff --git a/src/backend/nodes/copyfuncs.c b/src/backend/nodes/copyfuncs.c
@@ -3067,6 +3067,7 @@ _copyObjectWithArgs(const ObjectWithArgs *from)
 
 	COPY_NODE_FIELD(objname);
 	COPY_NODE_FIELD(objargs);
+	COPY_SCALAR_FIELD(args_unspecified);
 
 	return newnode;
 }
diff --git a/src/backend/nodes/equalfuncs.c b/src/backend/nodes/equalfuncs.c
@@ -1119,6 +1119,7 @@ _equalObjectWithArgs(const ObjectWithArgs *a, const ObjectWithArgs *b)
 {
 	COMPARE_NODE_FIELD(objname);
 	COMPARE_NODE_FIELD(objargs);
+	COMPARE_SCALAR_FIELD(args_unspecified);
 
 	return true;
 }
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
@@ -7202,6 +7202,33 @@ function_with_argtypes:
 					n->objargs = extractArgTypes($2);
 					$$ = n;
 				}
+			/*
+			 * Because of reduce/reduce conflicts, we can't use func_name
+			 * below, but we can write it out the long way, which actually
+			 * allows more cases.
+			 */
+			| type_func_name_keyword
+				{
+					ObjectWithArgs *n = makeNode(ObjectWithArgs);
+					n->objname = list_make1(makeString(pstrdup($1)));
+					n->args_unspecified = true;
+					$$ = n;
+				}
+			| ColId
+				{
+					ObjectWithArgs *n = makeNode(ObjectWithArgs);
+					n->objname = list_make1(makeString($1));
+					n->args_unspecified = true;
+					$$ = n;
+				}
+			| ColId indirection
+				{
+					ObjectWithArgs *n = makeNode(ObjectWithArgs);
+					n->objname = check_func_name(lcons(makeString($1), $2),
+												  yyscanner);
+					n->args_unspecified = true;
+					$$ = n;
+				}
 		;
 
 /*
diff --git a/src/backend/parser/parse_func.c b/src/backend/parser/parse_func.c
@@ -1895,8 +1895,10 @@ func_signature_string(List *funcname, int nargs,
 
 /*
  * LookupFuncName
- *		Given a possibly-qualified function name and a set of argument types,
- *		look up the function.
+ *
+ * Given a possibly-qualified function name and optionally a set of argument
+ * types, look up the function.  Pass nargs == -1 to indicate that no argument
+ * types are specified.
  *
  * If the function name is not schema-qualified, it is sought in the current
  * namespace search path.
@@ -1914,6 +1916,35 @@ LookupFuncName(List *funcname, int nargs, const Oid *argtypes, bool noError)
 
 	clist = FuncnameGetCandidates(funcname, nargs, NIL, false, false, noError);
 
+	/*
+	 * If no arguments were specified, the name must yield a unique candidate.
+	 */
+	if (nargs == -1)
+	{
+		if (clist)
+		{
+			if (clist->next)
+			{
+				if (!noError)
+					ereport(ERROR,
+							(errcode(ERRCODE_AMBIGUOUS_FUNCTION),
+							 errmsg("function name \"%s\" is not unique",
+									NameListToString(funcname)),
+							 errhint("Specify the argument list to select the function unambiguously.")));
+			}
+			else
+				return clist->oid;
+		}
+		else
+		{
+			if (!noError)
+				ereport(ERROR,
+						(errcode(ERRCODE_UNDEFINED_FUNCTION),
+						 errmsg("could not find a function named \"%s\"",
+								NameListToString(funcname))));
+		}
+	}
+
 	while (clist)
 	{
 		if (memcmp(argtypes, clist->args, nargs * sizeof(Oid)) == 0)
@@ -1962,7 +1993,7 @@ LookupFuncWithArgs(ObjectWithArgs *func, bool noError)
 		args_item = lnext(args_item);
 	}
 
-	return LookupFuncName(func->objname, argcount, argoids, noError);
+	return LookupFuncName(func->objname, func->args_unspecified ? -1 : argcount, argoids, noError);
 }
 
 /*
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
@@ -1811,6 +1811,9 @@ typedef struct ObjectWithArgs
 	NodeTag		type;
 	List	   *objname;		/* qualified name of function/operator */
 	List	   *objargs;		/* list of Typename nodes */
+	bool		args_unspecified; /* argument list was omitted, so name must
+								   * be unique (note that objargs == NIL means
+								   * zero args) */
 } ObjectWithArgs;
 
 /*
diff --git a/src/test/regress/expected/create_function_3.out b/src/test/regress/expected/create_function_3.out
diff --git a/src/test/regress/sql/create_function_3.sql b/src/test/regress/sql/create_function_3.sql
