Add reference for rpc with array literals

Fixes https://github.com/PostgREST/postgrest-docs/issues/258

api.rst

@@ -912,16 +912,6 @@ For instance, assume we have created this function in the database.
    SELECT a + b;
   $$ LANGUAGE SQL IMMUTABLE;
 
-The client can call it by posting an object like
-
-.. code-block:: http
-
-  POST /rpc/add_them HTTP/1.1
-
-  { "a": 1, "b": 2 }
-
-  3
-
 .. important::
 
   Whenever you create or change a function you must refresh PostgREST's schema cache. See the section :ref:`schema_reloading`.
@@ -938,25 +928,18 @@ The client can call it by posting an object like
       "message":"function test.add_them(a => text, b => text) does not exist"
      }
 
-You can also call a function that takes a single parameter of type json by sending the header :code:`Prefer: params=single-object` with your request. That way the JSON request body will be used as the single argument.
-
-.. code-block:: plpgsql
-
-  CREATE FUNCTION mult_them(param json) RETURNS int AS $$
-    SELECT (param->>'x')::int * (param->>'y')::int
-  $$ LANGUAGE SQL;
+The client can call it by posting an object like
 
 .. code-block:: http
 
-  POST /rpc/mult_them HTTP/1.1
-  Prefer: params=single-object
+  POST /rpc/add_them HTTP/1.1
 
-  { "x": 4, "y": 2 }
+  { "a": 1, "b": 2 }
 
-  8
+  3
 
 
-Procedures must be declared with named parameters, procedures declared like:
+Procedures must be declared with named parameters. Procedures declared like:
 
 .. code-block:: plpgsql
 
@@ -972,26 +955,6 @@ Note that PostgreSQL converts identifier names to lowercase unless you quote the
 
 PostgreSQL has four procedural languages that are part of the core distribution: PL/pgSQL, PL/Tcl, PL/Perl, and PL/Python. There are many other procedural languages distributed as additional extensions. Also, plain SQL can be used to write functions (as shown in the example above).
 
-.. note::
-
-  For versions prior to PostgreSQL 10, to pass a PostgreSQL native array you need to quote it as a string:
-
-  .. code-block:: http
-
-    POST /rpc/native_array_func HTTP/1.1
-
-    { "arg": "{1,2,3}" }
-
-  In these versions we recommend using function arguments of type json to accept arrays from the client:
-
-  .. code-block:: http
-
-    POST /rpc/json_array_func HTTP/1.1
-
-    { "arg": [1,2,3] }
-
-  Starting from PostgreSQL 10, a json array from the client gets mapped normally to a PostgreSQL native array.
-
 .. note::
 
   Why the `/rpc` prefix? One reason is to avoid name collisions between views and procedures. It also helps emphasize to API consumers that these functions are not normal restful things. The functions can have arbitrary and surprising behavior, not the standard "post creates a resource" thing that users expect from the other routes.
@@ -1013,6 +976,66 @@ Because ``add_them`` was declared IMMUTABLE, we can alternately call the functio
 
 The function parameter names match the JSON object keys in the POST case, for the GET case they match the query parameters ``?a=1&b=2``.
 
+Calling functions with a single json parameter
+----------------------------------------------
+
+You can also call a function that takes a single parameter of type json by sending the header :code:`Prefer: params=single-object` with your request. That way the JSON request body will be used as the single argument.
+
+.. code-block:: plpgsql
+
+  CREATE FUNCTION mult_them(param json) RETURNS int AS $$
+    SELECT (param->>'x')::int * (param->>'y')::int
+  $$ LANGUAGE SQL;
+
+.. code-block:: http
+
+  POST /rpc/mult_them HTTP/1.1
+  Prefer: params=single-object
+
+  { "x": 4, "y": 2 }
+
+  8
+
+Calling functions with array parameters
+---------------------------------------
+
+You can call a function that takes an array parameter:
+
+.. code-block:: plpgsql
+
+   CREATE FUNCTION native_array_func(arr int[]) RETURNS int[] as $$
+      SELECT arr;
+   $$ LANGUAGE SQL;
+
+.. code-block:: http
+
+ POST /rpc/native_array_func HTTP/1.1
+
+ { "arg": [1,2,3] }
+
+ [1,2,3]
+
+.. note::
+
+   For versions prior to PostgreSQL 10, to pass a PostgreSQL native array you need to quote it as a string:
+
+   .. code-block:: http
+
+    POST /rpc/native_array_func HTTP/1.1
+
+    { "arg": "{1,2,3}" }
+
+   In these versions we recommend using function parameters of type json to accept arrays from the client.
+
+For calling it with GET, you can pass the array as an `array literal <https://www.postgresql.org/docs/11/arrays.html#ARRAYS-INPUT>`_;
+as in ``{1,2,3}``. Note that the curly brackets have to be urlencoded(``{`` is ``%7B`` and ``}`` is ``%7D``).
+
+.. code-block:: http
+
+ GET /rpc/native_array_func?arr=%7B1,2,3%7D' HTTP/1.1
+
+ [1,2,3]
+
 Scalar functions
 ----------------