Обсуждение: element from an array by its index

On Tue, Jul 21, 2009 at 04:08:51PM +0600, Murat Kabilov wrote:
> I would like to know if there is a function that extracts an element by its
> index from an array?

No, the syntax most people expect and use would be arr[ndx].  If you
want a function, it would be easy to do:

  CREATE FUNCTION array_index(anyarray,int)
      RETURNS anyelement IMMUTABLE
      LANGUAGE sql AS $$
    SELECT $1[$2]; $$;

--
  Sam  http://samason.me.uk/

On Tue, Jul 21, 2009 at 10:47 AM, Sam Mason<sam@samason.me.uk> wrote:
> On Tue, Jul 21, 2009 at 04:08:51PM +0600, Murat Kabilov wrote:
>> I would like to know if there is a function that extracts an element by its
>> index from an array?
>
> No, the syntax most people expect and use would be arr[ndx].  If you
> want a function, it would be easy to do:
>
>  CREATE FUNCTION array_index(anyarray,int)
>      RETURNS anyelement IMMUTABLE
>      LANGUAGE sql AS $$
>    SELECT $1[$2]; $$;

but, why would you write a function to do this?

merlin

On Tue, Jul 21, 2009 at 02:29:12PM -0400, Merlin Moncure wrote:
> On Tue, Jul 21, 2009 at 10:47 AM, Sam Mason<sam@samason.me.uk> wrote:
> > On Tue, Jul 21, 2009 at 04:08:51PM +0600, Murat Kabilov wrote:
> >> I would like to know if there is a function that extracts an element by its
> >> index from an array?
> >
> > No, the syntax most people expect and use would be arr[ndx].  If you
> > want a function, it would be easy to do:
> >
> >   CREATE FUNCTION array_index(anyarray,int)
> >       RETURNS anyelement IMMUTABLE
> >       LANGUAGE sql AS $$
> >     SELECT $1[$2]; $$;
>
> but, why would you write a function to do this?

No idea, my guess was that Murat is driving PG through some other code
and this expected to generate function-call style syntax for everything,
including array indexing.

I'd be interested to know the real reason as well!

--
  Sam  http://samason.me.uk/