Thread: Counting elements of an array

Good morning all,

I would like to know how I can get the number of elements of an array.

regards,
Renaud THONNART

Christopher Sawtell wrote:

> On Thu, 01 Mar 2001 21:53, you wrote:
> > Good morning all,
> >
> > I would like to know how I can get the number of elements of an array.
>
> create function array_element_count(_int4) returns integer as '
>  declare
>   a alias for $1;
>   i integer;
>  begin
>   i := 1;
>   while a[i] loop
>    i := i+1;
>   end loop;
>  return i-1;
>  end;' language 'plpgsql' with(isstrict,iscachable);
>

Thanks a lot
Regards, Renaud THONNART

Renaud Tthonnart <thonnart@amwdb.u-strasbg.fr> writes:
> I would like to know how I can get the number of elements of an array.

There is a function that returns an array's dimensions as a text string:

regression=# select array_dims( '{1,2,3}'::int[] );
 array_dims
------------
 [1:3]
(1 row)

regression=# select array_dims( '{{1,2,3},{4,5,6}}'::int[] );
 array_dims
------------
 [1:2][1:3]
(1 row)


            regards, tom lane

Tom Lane wrote:

> Renaud Tthonnart <thonnart@amwdb.u-strasbg.fr> writes:
> > I would like to know how I can get the number of elements of an array.
>
> There is a function that returns an array's dimensions as a text string:
>
> regression=# select array_dims( '{1,2,3}'::int[] );
>  array_dims
> ------------
>  [1:3]
> (1 row)
>
> regression=# select array_dims( '{{1,2,3},{4,5,6}}'::int[] );
>  array_dims
> ------------
>  [1:2][1:3]
> (1 row)
>
>                         regards, tom lane

Thanks very much Tom,  you have helped me a lot.
Renaud THONNART

Tom Lane wrote:

> Renaud Tthonnart <thonnart@amwdb.u-strasbg.fr> writes:
> > I would like to know how I can get the number of elements of an array.
>
> There is a function that returns an array's dimensions as a text string:
>
> regression=# select array_dims( '{1,2,3}'::int[] );
>  array_dims
> ------------
>  [1:3]
> (1 row)
>
> regression=# select array_dims( '{{1,2,3},{4,5,6}}'::int[] );
>  array_dims
> ------------
>  [1:2][1:3]
> (1 row)
>
>                         regards, tom lane

Ok Tom, but if I have a table (for example aaa) that contains an array (for
example vector)

The function that you have spoken to me doesn't work:

select array_dims(vector) from aaa;
or
select array_dims(vector :: int[]) from aaa;

The result is :

 array_dims
------------



(3 row)

There isn't  any parse error but it don't work.

Do I have badly understand what you have explain me?

Thank you,
Renaud THONNART

Sorry!!
It works very well!

Renaud THONNART


> Renaud Tthonnart <thonnart@amwdb.u-strasbg.fr> writes:
> > I would like to know how I can get the number of elements of an array.
>
> There is a function that returns an array's dimensions as a text string:
>
> regression=# select array_dims( '{1,2,3}'::int[] );
>  array_dims
> ------------
>  [1:3]
> (1 row)
>
> regression=# select array_dims( '{{1,2,3},{4,5,6}}'::int[] );
>  array_dims
> ------------
>  [1:2][1:3]
> (1 row)
>
>                         regards, tom lane