Allow referring to functions without arguments when unique

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 <michael.paquier@gmail.com>

10 files changed, 59 insertions, 24 deletions

diff --git a/doc/src/sgml/ref/alter_extension.sgml b/doc/src/sgml/ref/alter_extension.sgml
index de6d6dca16b..a7c0927d1c9 100644
--- 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
index 0388d06b959..168eeb7c526 100644
--- 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
index 4511c7f7b24..0bafe5b8f80 100644
--- 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
index c1cf587cb29..7483c8c03fc 100644
--- 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
index 11266755e56..a7d13edc22b 100644
--- 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>)
@@ -192,7 +192,7 @@ 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>
@@ -200,6 +200,8 @@ SELECT CAST ( 2 AS numeric ) + 4.0;
        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
index f44ee89d33c..647c3b9f057 100644
--- 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
index 5969b084b44..0aa984528d3 100644
--- 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
index d8ca39f869e..9fb4c2fd7e3 100644
--- 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
index fc00129620b..ce532543f0b 100644
--- 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
index 998fe3b7c03..afd86aff3a0 100644
--- 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> |