Обсуждение: BUG #18621: postgres_fdw cannot work with tables that use schemaless functions in triggers
BUG #18621: postgres_fdw cannot work with tables that use schemaless functions in triggers
От
PG Bug reporting form
Дата:
The following bug has been logged on the website:
Bug reference: 18621
Logged by: RekGRpth
Email address: rekgrpth@gmail.com
PostgreSQL version: 16.4
Operating system: docker alpine
Description:
Let's create a trigger on a remote server that uses different functions for
different users. postgres_fdw cannot perform an insert in this case. And the
remote server may be a production server, where there is no access to change
the trigger code so that it uses an explicit schema specification!
drop database local;
drop database remote;
drop user alice;
drop user bob;
drop user local;
drop user remote;
create user alice superuser;
create user bob superuser;
create user local superuser;
create user remote superuser;
create database local with owner local;
create database remote with owner remote;
\connect "user=remote dbname=remote"
create table remote (i int, t text);
create schema remote;
truncate table remote;
create function multiply(i int) returns int language plpgsql as $body$
begin
return i * 1;
end;$body$;
create schema alice;
create function alice.multiply(i int) returns int language plpgsql as $body$
begin
return i * 2;
end;$body$;
create schema bob;
create function bob.multiply(i int) returns int language plpgsql as $body$
begin
return i * 3;
end;$body$;
create function remote_trigger() returns trigger language plpgsql as $body$
begin
if tg_when = 'BEFORE' and tg_op in ('INSERT', 'UPDATE') then
new.i = multiply(new.i);
new.t = current_user;
end if;
return case when tg_op = 'DELETE' then old else new end;
end;$body$;
create trigger remote_before_trigger before insert or update or delete on
remote for each row execute procedure remote_trigger();
create trigger remote_after_trigger after insert or update or delete on
remote for each row execute procedure remote_trigger();
insert into remote select 1;
\connect "user=bob dbname=remote"
insert into remote select 1;
\connect "user=alice dbname=remote"
insert into remote select 1;
\connect "user=local dbname=local"
create schema fdw;
create extension postgres_fdw schema fdw;
create server remote foreign data wrapper postgres_fdw options (dbname
'remote');
create user mapping for current_user server remote options (user
'remote');
create user mapping for alice server remote options (user 'remote');
create user mapping for bob server remote options (user 'remote');
create foreign table remote (i int, t text) server remote options
(schema_name 'public', table_name 'remote');
select * from remote;
\connect "user=bob dbname=local"
insert into remote select i from generate_series(1, 10) i;
ERROR: function multiply(integer) does not exist
HINT: No function matches the given name and argument types. You might need
to add explicit type casts.
CONTEXT: PL/pgSQL function remote.remote_trigger() line 3 at assignment
remote SQL command: INSERT INTO public.remote(i, t) VALUES ($1, $2)
On Tue, 2024-09-17 at 05:28 +0000, PG Bug reporting form wrote:
> Let's create a trigger on a remote server that uses different functions for
> different users. postgres_fdw cannot perform an insert in this case. And the
> remote server may be a production server, where there is no access to change
> the trigger code so that it uses an explicit schema specification!
>
> [...]
> create function multiply(i int) returns int language plpgsql as $body$
> begin
> return i * 1;
> end;$body$;
> create schema alice;
> create function alice.multiply(i int) returns int language plpgsql as $body$
> begin
> return i * 2;
> end;$body$;
> create schema bob;
> create function bob.multiply(i int) returns int language plpgsql as $body$
> begin
> return i * 3;
> end;$body$;
> create function remote_trigger() returns trigger language plpgsql as $body$
> begin
> if tg_when = 'BEFORE' and tg_op in ('INSERT', 'UPDATE') then
> new.i = multiply(new.i);
> new.t = current_user;
> end if;
> return case when tg_op = 'DELETE' then old else new end;
> end;$body$;
> create trigger remote_before_trigger before insert or update or delete on
> remote for each row execute procedure remote_trigger();
>
> [...]
>
> create extension postgres_fdw schema fdw;
> create server remote foreign data wrapper postgres_fdw options (dbname
> 'remote');
> create user mapping for current_user server remote options (user
> 'remote');
> create user mapping for alice server remote options (user 'remote');
> create user mapping for bob server remote options (user 'remote');
> create foreign table remote (i int, t text) server remote options
> (schema_name 'public', table_name 'remote');
> select * from remote;
>
> \connect "user=bob dbname=local"
> insert into remote select i from generate_series(1, 10) i;
>
> ERROR: function multiply(integer) does not exist
> HINT: No function matches the given name and argument types. You might need
> to add explicit type casts.
> CONTEXT: PL/pgSQL function remote.remote_trigger() line 3 at assignment
> remote SQL command: INSERT INTO public.remote(i, t) VALUES ($1, $2)
That is documented
(https://www.postgresql.org/docs/current/postgres-fdw.html#POSTGRES-FDW-REMOTE-QUERY-EXECUTION-ENVIRONMENT)
"In the remote sessions opened by postgres_fdw, the search_path parameter
is set to just pg_catalog, so that only built-in objects are visible without
schema qualification. This is not an issue for queries generated by
postgres_fdw itself, because it always supplies such qualification.
However, this can pose a hazard for functions that are executed on the
remote server via triggers or rules on remote tables. For example, if a
remote table is actually a view, any functions used in that view will be
executed with the restricted search path. It is recommended to schema-qualify
all names in such functions, or else attach SET search_path options (see
CREATE FUNCTION) to such functions to establish their expected search path
environment."
So I don't see a bug here.
Yours,
Laurenz Albe
Yes, but as you can see above, the same insert works when connected
directly and does not work when connected via postgres_fdw.
Moreover, if I set search_path to the default value "$user", public ,
then everything starts working fine.
вт, 17 сент. 2024 г. в 14:19, Laurenz Albe <laurenz.albe@cybertec.at>:
>
> On Tue, 2024-09-17 at 05:28 +0000, PG Bug reporting form wrote:
> > Let's create a trigger on a remote server that uses different functions for
> > different users. postgres_fdw cannot perform an insert in this case. And the
> > remote server may be a production server, where there is no access to change
> > the trigger code so that it uses an explicit schema specification!
> >
> > [...]
> > create function multiply(i int) returns int language plpgsql as $body$
> > begin
> > return i * 1;
> > end;$body$;
> > create schema alice;
> > create function alice.multiply(i int) returns int language plpgsql as $body$
> > begin
> > return i * 2;
> > end;$body$;
> > create schema bob;
> > create function bob.multiply(i int) returns int language plpgsql as $body$
> > begin
> > return i * 3;
> > end;$body$;
> > create function remote_trigger() returns trigger language plpgsql as $body$
> > begin
> > if tg_when = 'BEFORE' and tg_op in ('INSERT', 'UPDATE') then
> > new.i = multiply(new.i);
> > new.t = current_user;
> > end if;
> > return case when tg_op = 'DELETE' then old else new end;
> > end;$body$;
> > create trigger remote_before_trigger before insert or update or delete on
> > remote for each row execute procedure remote_trigger();
> >
> > [...]
> >
> > create extension postgres_fdw schema fdw;
> > create server remote foreign data wrapper postgres_fdw options (dbname
> > 'remote');
> > create user mapping for current_user server remote options (user
> > 'remote');
> > create user mapping for alice server remote options (user 'remote');
> > create user mapping for bob server remote options (user 'remote');
> > create foreign table remote (i int, t text) server remote options
> > (schema_name 'public', table_name 'remote');
> > select * from remote;
> >
> > \connect "user=bob dbname=local"
> > insert into remote select i from generate_series(1, 10) i;
> >
> > ERROR: function multiply(integer) does not exist
> > HINT: No function matches the given name and argument types. You might need
> > to add explicit type casts.
> > CONTEXT: PL/pgSQL function remote.remote_trigger() line 3 at assignment
> > remote SQL command: INSERT INTO public.remote(i, t) VALUES ($1, $2)
>
> That is documented
> (https://www.postgresql.org/docs/current/postgres-fdw.html#POSTGRES-FDW-REMOTE-QUERY-EXECUTION-ENVIRONMENT)
>
> "In the remote sessions opened by postgres_fdw, the search_path parameter
> is set to just pg_catalog, so that only built-in objects are visible without
> schema qualification. This is not an issue for queries generated by
> postgres_fdw itself, because it always supplies such qualification.
> However, this can pose a hazard for functions that are executed on the
> remote server via triggers or rules on remote tables. For example, if a
> remote table is actually a view, any functions used in that view will be
> executed with the restricted search path. It is recommended to schema-qualify
> all names in such functions, or else attach SET search_path options (see
> CREATE FUNCTION) to such functions to establish their expected search path
> environment."
>
> So I don't see a bug here.
>
> Yours,
> Laurenz Albe
On Tue, 2024-09-17 at 14:39 +0500, RekGRpth wrote: > Yes, but as you can see above, the same insert works when connected > directly and does not work when connected via postgres_fdw. Yes, that's how it should be. Yours, Laurenz Albe
PG Bug reporting form <noreply@postgresql.org> writes:
> Let's create a trigger on a remote server that uses different functions for
> different users. postgres_fdw cannot perform an insert in this case. And the
> remote server may be a production server, where there is no access to change
> the trigger code so that it uses an explicit schema specification!
This is a bug in the trigger function, not in postgres_fdw.
regards, tom lane