Re: Array aggregation. Was: PostgreSQL Final Release ... Monday?

It is used as an aggregation function. It only works on integers, and assumes
sizeof(int) == sizeof(void *)

There are two functions:

int_array_aggregate(int4)
and
int_array_enum(int4[])

One creates an integer array as:

create table tst as select some_field, int_array_aggregate(int_field) as field
from table group by some_field;

This will poduce one row for all the unique "some_fields" with an array of all
"int_field" associated.

To extract this, you use int_array_enum(int_array); whic returns multiple
results.

Hannu Krosing wrote:
>
> On Thu, 2002-01-31 at 02:36, mlw wrote:
> >
> > I submitted a "contrib" project for integer array
> > aggregation/enumeration. I didn't see it in rc2.
> >
>
> Some general questions about arrays -
>
> 1. Could this aggregation/enumeration be done in a generic way, so
> that you could aggregate over any array ?
>
> The only generic function I currently know of is count(), but it
> is generic only on argument side, i.e count(any) returns always
> integer.
>
> 2. Is there a way to define a function such that
>
> declare make_array(any) returns any[] ?
>
> 3. Also, can I prescribe order of aggregation (aggregation applied
> _after_ ORDER BY) that would act in a way similar to HAVING .
>
> 4. what arguments must I give to array_in so that it produces an
> array of specific kind ? I tried some more obvious things and
> really got nowhere.
>
> --------------
> Hannu
>
> PS. I attach an alpha-contrib ofPL/PgSQL code to compare intarrays.
> I have not had time to tie these ops to indexes
>
> --------------
> Hannu
>
> -------------------------------------------------------------------------------
> Name: ARRAY_COMP.SQL
> ARRAY_COMP.SQL Type: text/x-sql
> Encoding: quoted-printable