Fix concat() and format() to handle VARIADIC-labeled arguments correctly.

Previously, the VARIADIC labeling was effectively ignored, but now these
functions act as though the array elements had all been given as separate
arguments.

Pavel Stehule

2 files changed, 29 insertions, 6 deletions

diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index 35c7f75eab2..e9dbcb9f8a0 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -1394,7 +1394,8 @@
        </entry>
        <entry><type>text</type></entry>
        <entry>
-        Concatenate all arguments. NULL arguments are ignored.
+        Concatenate the text representations of all the arguments.
+        NULL arguments are ignored.
        </entry>
        <entry><literal>concat('abcde', 2, NULL, 22)</literal></entry>
        <entry><literal>abcde222</literal></entry>
@@ -1411,8 +1412,8 @@
        </entry>
        <entry><type>text</type></entry>
        <entry>
-        Concatenate all but first arguments with separators. The first
-        parameter is used as a separator. NULL arguments are ignored.
+        Concatenate all but the first argument with separators. The first
+        argument is used as the separator string. NULL arguments are ignored.
        </entry>
        <entry><literal>concat_ws(',', 'abcde', 2, NULL, 22)</literal></entry>
        <entry><literal>abcde,2,22</literal></entry>
@@ -1522,8 +1523,9 @@
        </entry>
        <entry><type>text</type></entry>
        <entry>
-         Format a string.  This function is similar to the C function
-         <function>sprintf</>; but only the following conversion specifications
+         Format arguments according to a format string.
+         This function is similar to the C function
+         <function>sprintf</>, but only the following conversion specifications
          are recognized: <literal>%s</literal> interpolates the corresponding
          argument as a string; <literal>%I</literal> escapes its argument as
          an SQL identifier; <literal>%L</literal> escapes its argument as an
@@ -2034,6 +2036,18 @@
    </table>
 
    <para>
+    The <function>concat</function>, <function>concat_ws</function> and
+    <function>format</function> functions are variadic, so it is possible to
+    pass the values to be concatenated or formatted as an array marked with
+    the <literal>VARIADIC</literal> keyword (see <xref
+    linkend="xfunc-sql-variadic-functions">).  The array's elements are
+    treated as if they were separate ordinary arguments to the function.
+    If the variadic array argument is NULL, <function>concat</function>
+    and <function>concat_ws</function> return NULL, but
+    <function>format</function> treats a NULL as a zero-element array.
+   </para>
+
+   <para>
    See also the aggregate function <function>string_agg</function> in
    <xref linkend="functions-aggregate">.
    </para>
diff --git a/doc/src/sgml/xfunc.sgml b/doc/src/sgml/xfunc.sgml
index 85539feb0d2..4fb42842c6f 100644
--- a/doc/src/sgml/xfunc.sgml
+++ b/doc/src/sgml/xfunc.sgml
@@ -3153,6 +3153,10 @@ CREATE OR REPLACE FUNCTION retcomposite(IN integer, IN integer,
      <literal>fcinfo-&gt;flinfo</>. The parameter <literal>argnum</>
      is zero based.  <function>get_call_result_type</> can also be used
      as an alternative to <function>get_fn_expr_rettype</>.
+     There is also <function>get_fn_expr_variadic</>, which can be used to
+     find out whether the call contained an explicit <literal>VARIADIC</>
+     keyword.  This is primarily useful for <literal>VARIADIC "any"</>
+     functions, as described below.
     </para>
 
     <para>
@@ -3229,7 +3233,12 @@ CREATE FUNCTION make_array(anyelement) RETURNS anyarray
      as happens with normal variadic functions; they will just be passed to
      the function separately.  The <function>PG_NARGS()</> macro and the
      methods described above must be used to determine the number of actual
-     arguments and their types when using this feature.
+     arguments and their types when using this feature.  Also, users of such
+     a function might wish to use the <literal>VARIADIC</> keyword in their
+     function call, with the expectation that the function would treat the
+     array elements as separate arguments.  The function itself must implement
+     that behavior if wanted, after using <function>get_fn_expr_variadic</> to
+     detect that the actual argument was marked with <literal>VARIADIC</>.
     </para>
    </sect2>