Postgres 9.6

By using db<>fiddle, you agree to license everything you submit by Creative Commons CC0.

Help with an interesting Postgres question: Why isn't an Index Only Scan used on a partition accessed via the parent table?.

create type t1 as (a int2, b text, c boolean);
create type t2 as (a t1, b boolean);
create type t3 as (a t2, b int4);
-- Now, how can I do the following for a variable x of type t3:

DO LANGUAGE PLPGSQL
$$
DECLARE 
    x t3 ;
    y boolean ;
    z t3 ;
BEGIN
    z := x ;           -- Works
    x.a.a.c := true;   -- Syntax error
    y := x.a.a.c;
END ;
$$
ERROR:  syntax error at or near "x"
LINE 11:     x.a.a.c := true;   -- Syntax error
             ^


DO LANGUAGE PLPGSQL
$$
DECLARE 
    x t3 ;
    z t3 ;
BEGIN
    x.a := z.a ;
END ;
$$
DO LANGUAGE PLPGSQL
$$
DECLARE 
    x t3 ;
    z t3 ;
BEGIN
    x.a.a := z.a.a ;
END ;
$$
ERROR:  "x.a.a" is not a known variable
LINE 7:     x.a.a := z.a.a ;
            ^


DO LANGUAGE PLPGSQL
$$
DECLARE 
    x t3 ;
    z t3 ;
BEGIN
    (x.a).a := z.a.a ;
END ;
$$
ERROR:  syntax error at or near "("
LINE 7:     (x.a).a := z.a.a ;
            ^