Possible trigger bug? function call argument literalised

Hi

I created a table with trigger and according trigger and trigger function as

drop table if exists CALCULATION_METHOD cascade;
create table CALCULATION_METHOD (ID
uuid
not null
default uuid_generate_v4(),
METHOD_NAME
text
not null,
DB_ROUTINE_NAME
name
not null,
ENTRY_PIT
timestamptz
not null
default transaction_timestamp(),
REMARKS
text,
constraint CALCULATION_METHOD_PK
primary key (ID),
constraint CALCULATION_METHOD_UQ
unique (DB_ROUTINE_NAME));

create or replace function METHOD_CHECK()
returns trigger
language plpgsql
stable
as
$body$
declare
V_COUNT smallint;
begin
if TG_NARGS != 1 then
raise
exception
using
message = 'METHOD_CHECK expects the schema name to be
passed and nothing more! There have been passed ' ||
TG_NARGS || ' arguments.',
hint = 'Please check the trigger "' || TG_NAME ||
'" on table "' || TG_TABLE_NAME || '" in schema "' ||
TG_TABLE_SCHEMA || '".';
end if;
select COUNT(*) into V_COUNT
from INFORMATION_SCHEMA.ROUTINES
where ROUTINE_SCHEMA = TG_ARGV[1]
and ROUTINE_NAME = NEW.DB_ROUTINE_NAME;
if V_COUNT != 1 then
raise exception ' expects the schema name to be passed!';
end if;
insert into TG_TABLE_SCHEMA.TG_TABLE_NAME values (NEW.*);
return NULL;
end;
$body$;

create trigger CALCULATION_METHOD_BR_IU
before insert on CALCULATION_METHOD
for each row
execute function METHOD_CHECK(current_schema);

Executing such, the string "current_schema" gets literalised, i.e.
single quoted:
norge=# \d calculation_method
Table "public.calculation_method"
Column | Type | Collation | Nullable |
Default
-----------------+--------------------------+-----------+----------+-------------------------
id | uuid | | not null |
uuid_generate_v4()
method_name | text | | not null |
db_routine_name | name | | not null |
entry_pit | timestamp with time zone | | not null |
transaction_timestamp()
remarks | text | | |
Indexes:
"calculation_method_pk" PRIMARY KEY, btree (id)
"calculation_method_uq" UNIQUE CONSTRAINT, btree (db_routine_name)
Triggers:
calculation_method_br_iu BEFORE INSERT ON calculation_method FOR
EACH ROW EXECUTE FUNCTION method_check('current_schema')

I am using
norge=# select version();
version
----------------------------------------------------------------------------------------------------------------------------------------------------
PostgreSQL 12.5 on x86_64-suse-linux-gnu, compiled by gcc (SUSE
Linux) 10.2.1 20201028 [revision
a78cd759754c92cecbf235ac9b447dcdff6c6e2f], 64-bit

I strongly feel this is a bug, at least no intention at all from my
side. However, before filing a bug, I wanted to get your opinion on
that. Maybe it is just a problem of the openSUSE Tumbleweed repository.

I would appreciate your two dimes. Kind regards

Thiemo

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