PostgreSQL Parametric Window Size

Question

Does anyone know if SQL and PostgreSQL standards will be defined (10.x or higher) Parametric window size ?

MVE times of what I call the parametric window size:

WITH

D AS (SELECT T.x::FLOAT FROM generate_series(0., 10., 0.1) AS T(x)),
W AS (SELECT 10 AS WindowSize)

SELECT
    D.x
   ,AVG(D.x) OVER (ROWS BETWEEN W.WindowSize PRECEDING AND CURRENT ROW)
FROM
    D, W;

Which causes the following error:

ERROR:  argument of ROWS must not contain variables
LINE 8:    ,AVG(D.x) OVER (ROWS BETWEEN W.WindowSize PRECEDING AND C...
                                        ^
********** Error **********

ERROR: argument of ROWS must not contain variables
SQL State: 42P10

I understand that a parametric window is quite difficult to implement. And I know that I can get around some aspects of this limitation using Dynamic Query and PL / PGSQL.

My questions:

• Are SQL standards defining such a thing?
• Will PostgreSQL implement it (if so, when is it planned)?
• If not, what limitations should be overcome before using such a function?

Answer 1

No, this is not standard SQL.

BNF:

http://jakewheat.imtqy.com/sql-overview/sql-2008-foundation-grammar.html#window-frame-preceding

<window frame preceding> ::=
  <unsigned value specification> PRECEDING

<unsigned value specification> . , .