Re: join of array

Tom Lane wrote:
> Pavel Stehule <stehule@kix.fsv.cvut.cz> writes:
>
>>Is possible merge two arrays like
>>array[1,2,3] + array[4,5,6] => array[1,2,3,4,5,6]
>
>
> I was about to say that || would do it, but I see that's not quite
> right:
>
> regression=# SELECT ARRAY[1,2,3] || ARRAY[4,5,6];
>      ?column?
> -------------------
>  {{1,2,3},{4,5,6}}
> (1 row)
>
> Offhand, I would think that '{1,2,3,4,5,6}' would be what I'd
> intuitively expect to get from "concatenating" these arrays.
> Joe, do we really have this implemented per spec?
>

Hmmm, it made sense to me, at at least at some point ;-). Here's the
SQL99 guidance (SQL200X doesn't give any more detailed guidance):

4.11.3.2 Operators that operate on array values and return array values
<array concatenation> is an operation that returns the array value made
by joining its array value operands in the order given.

So I guess it ought to be changed.

We also have
   ARRAY[1,2] || 3 == '{1,2,3}'
and
   ARRAY[[1,2],[3,4]] || ARRAY[5,6] == '{{1,2},{3,4},{5,6}}'
and
   ARRAY[[1,2],[3,4]] || ARRAY[[1,2],[3,4]] ==
                                '{{{1,2},{3,4}},{{1,2},{3,4}}}'

I think the first two still make sense. I guess the third case ought to be:
   ARRAY[[1,2],[3,4]] || ARRAY[[1,2],[3,4]] ==
                                '{{1,2},{3,4},{1,2},{3,4}}'
?

If this sounds good, I'll work on a patch for the behavior as well as
the docs.

Joe