Re: Undocumented array_val[generate_series(...)] functionality?

> On Jul 11, 2021, at 5:52 PM, David G. Johnston <david(dot)g(dot)johnston(at)gmail(dot)com> wrote:
>
> 
> Hey,
>
> A post over in Reddit had an expression form I've never seen before:
>
> select (array[1,2,3,4]::integer[])[generate_series(1, 3)];
> ===
> 1
> 2
> 3
>
> Looking at subscripting in the SQL syntax this example doesn't seem to be documented.
>
> https://www.postgresql.org/docs/current/sql-expressions.html#SQL-EXPRESSIONS-SUBSCRIPTS
>
> Is it documented somewhere else, and, regardless, shouldn't it be documented in the linked location?
>
> I get this is basically a variant of the slice syntax [n:m], and it is working as expected, but nothing indicates I can put an SRF inside the brackets.
>
> David J.
Is that expression saying something like select the first second third element from array 1,2,3,4?

>