last year I did a performance audit of some applications and I found a new relatively common pattern - iteration over jsonb arrays. Because PL/pgSQL doesn't support this iteration directly, they used some combinations of jsonb_array_elements function and FOR IN SELECT.
The overhead of this can be relatively high, and I think we can support FOREACH json(b) arrays without some high cost.
My idea is a support of syntax
FOREACH target IN JSON ARRAY expression LOOP .. END LOOP
I did some simple test
CREATE OR REPLACE FUNCTION public.randoma(integer) RETURNS integer[] LANGUAGE sql AS $function$ select array_agg(random()*10000) from generate_series(1,$1) $function$
CREATE OR REPLACE FUNCTION public.suma(integer[]) RETURNS integer LANGUAGE plpgsql IMMUTABLE AS $function$ declare s int default 0; f int; begin foreach f in array $1 loop s := s + f; end loop; return s; end; $function$
CREATE OR REPLACE FUNCTION public.sumj(jsonb) RETURNS integer LANGUAGE plpgsql IMMUTABLE AS $function$ declare s int default 0; f int; begin for f in select v from jsonb_array_elements($1) g(v) loop s := s + f::int; end loop; return s; end; $function$
(2026-01-24 12:20:07) postgres=# do $$ declare a int[] = randoma(10000); begin for i in 1..1000 loop perform suma(a); end loop; end; $$; DO Time: 2705,881 ms (00:02,706) (2026-01-24 12:20:11) postgres=# do $$ declare a jsonb = array_to_json(randoma(10000)); begin for i in 1..1000 loop perform sumj(a); end loop; end; $$; DO Time: 25809,319 ms (00:25,809)
FOREACH is +/- 10 times faster
target can be a scalar variable of any type - we can use cast rules used in JSON_TABLE
