pl/pgsql errors when multi-dimensional arrays are used

try:
a.fld1[1] = '[221,222,223,224]';

чт, 29 апр. 2021 г. в 10:35, PG Doc comments form <noreply@postgresql.org>:

This also returns ERROR:  invalid input syntax for type integer:
"[221,222,223,224]"

Hi

čt 29. 4. 2021 v 12:33 odesílatel Rafal Dabrowa <fatwildcat@gmail.com>
napsal:

This also returns ERROR: invalid input syntax for type integer:
"[221,222,223,224]"

On 4/29/2021 9:48 AM, KraSer wrote:

try:
a.fld1[1] = '[221,222,223,224]';

чт, 29 апр. 2021 г. в 10:35, PG Doc comments form
<noreply@postgresql.org <mailto:noreply@postgresql.org>>:

The following documentation comment has been logged on the website:

Page: https://www.postgresql.org/docs/13/arrays.html
Description:

I have PostgreSQL 13. Let's declare the type below, then use it in
pl/pgsql:

create type typ1 as (
fld1 int[][]
);

do $$
declare
a typ1;
begin
a.fld1 = '{{121,122,123,124}}'; -- OK
(1)
a.fld1[1] = '{221,222,223,224}'; -- fails
(2)
a.fld1[1][1] = 321; -- OK
(3)
a.fld1[1][2] = 322; -- OK unless line (1)
is removed
end;
$$;

In line (2) the plql reports ERROR: invalid input syntax for type
integer:
"{221,222,223,224}"
When lines (1) and (2) are removed, psql reports ERROR: array
subscript out
of range

Is this expected behavior? Why?

Rafal

Postgres's arrays don't allow any modification that creates some gap in
the array. Next - Postgres's arrays are multidimensional arrays, and these
arrays are not an arrays or arrays.

So your line (1) cannot work.

You can write

a.fld1[1][1:4] := '{221,222,223,224}';

Case (3) fails, because this operation on empty array creates gap on
position 1,1.

you can use an function array_fill

DO
postgres=# do $$
declare a int[];
begin
a := array_fill(null::int, array[2,2]);
a[1][2] := 322;

raise notice 'a=%', a;
end;
$$;
NOTICE: a={{NULL,322},{NULL,NULL}}

Regards

Pavel

PG Doc comments form <noreply@postgresql.org> writes:

I have PostgreSQL 13. Let's declare the type below, then use it in
pl/pgsql:

create type typ1 as (
fld1 int[][]
);

I think you have a fundamental misunderstanding of how multidimensional
arrays work in Postgres. There's no separate type for 2-D vs 1-D arrays;
that is, the extra pair of brackets you wrote above is just noise.
What matters is what you put into the array at runtime, and the syntax
you use to do it.

a.fld1 = '{{121,122,123,124}}'; -- OK (1)

Fine, you stored a 2-D array into fld1.

a.fld1[1] = '{221,222,223,224}'; -- fails (2)

This fails on semantic grounds because a non-slice assignment or fetch
of an int array element must store or retrieve an int. You're trying
to store an array slice, which requires that you use [m:n] subscript
notation. It'd be correct to write either of

a.fld1[1:4] = '{221,222,223,224}';
a.fld1[1:] = '{221,222,223,224}';

which unfortunately plpgsql doesn't support in released versions
(that's fixed for v14 though).

regards, tom lane