Thread: array faults?

Using arrays I came across some strangenesses. Probably this is well
known, but I couldn't find mentions of it.

I am under the impression that this should be an error. Am I wrong?

EXAMPLE 1:
maint=# select ('{{1,2,3},{4,5,6}}'::int[])[1][1:3];
    int4
-----------
  {{1,2,3}}
(1 row)

Shouldn't this have been just {1,2,3} ?

EXAMPLE 2:
maint=# select ('{{1,2,3},{4,5,6}}'::int[])[2][1:3];
    int4
-----------
  {{1,2,3},{4,5,6}}
(1 row)

Shouldn't this have been just {4,5,6} (or maybe {{4,5,6}} accepting the
result of example 1) ?


I am trying to do sth like:
    maint=# select 1 = any ('{{1,2,3},{4,5,6}}'::int[])[2][1:3];
But that is not working for obvious reasons. This makes arrays pretty
broken for me.

Am I missing anything obvious?

Regards,

David Helgason
Over the Edge Entertainments

David Helgason <david@uti.is> writes:
> EXAMPLE 1:
> maint=# select ('{{1,2,3},{4,5,6}}'::int[])[1][1:3];
>     int4
> -----------
>   {{1,2,3}}
> (1 row)

> Shouldn't this have been just {1,2,3} ?

Nope.  It's equivalent to (...)[1:1][1:3].  See section 8.10.3 "Accessing
Arrays" in the current documentation.  Note in particular where it says

 An array subscripting operation is always taken to represent an array
 slice if any of the subscripts are written in the form lower:upper. A
 lower bound of 1 is assumed for any subscript where only one value is
 specified, ...

> Shouldn't this have been just {4,5,6} (or maybe {{4,5,6}} accepting the
> result of example 1) ?

See above.  You need to write [2:2] not [2].

            regards, tom lane