--
-- test.sql
--
create extension pg_readonly;
--
select get_cluster_readonly();
 get_cluster_readonly 
----------------------
 f
(1 row)

select unset_cluster_readonly();
 unset_cluster_readonly 
------------------------
 t
(1 row)

--
drop table t;
ERROR:  table "t" does not exist
drop function f;
ERROR:  could not find a function named "f"
--
create table t(i int);
create function f(IN p int, OUT i int) returns int as $$
begin
    insert into t(i) values (f.p) returning t.i into f.i;
end$$
language plpgsql;
select set_cluster_readonly();
 set_cluster_readonly 
----------------------
 t
(1 row)

select * from t;
 i 
---
(0 rows)

insert into t values (1);
ERROR:  pg_readonly: pgro_main: invalid statement because cluster is read-only
select f(1);
ERROR:  pg_readonly: pgro_main: invalid statement because cluster is read-only
CONTEXT:  SQL statement "insert into t(i) values (f.p) returning t.i"
PL/pgSQL function f(integer) line 3 at SQL statement
-- However, in this same session, if you call f() before entering in read only mode, 
-- it is then able to write during read only mode:
select unset_cluster_readonly();
 unset_cluster_readonly 
------------------------
 t
(1 row)

select f(1);
 f 
---
 1
(1 row)

select set_cluster_readonly();
 set_cluster_readonly 
----------------------
 t
(1 row)

insert into t values (2);
ERROR:  pg_readonly: pgro_main: invalid statement because cluster is read-only
select f(2);
ERROR:  pg_readonly: pgro_exec: invalid statement because cluster is read-only
CONTEXT:  SQL statement "insert into t(i) values (f.p) returning t.i"
PL/pgSQL function f(integer) line 3 at SQL statement
select get_cluster_readonly();
 get_cluster_readonly 
----------------------
 t
(1 row)

select f(3);
ERROR:  pg_readonly: pgro_exec: invalid statement because cluster is read-only
CONTEXT:  SQL statement "insert into t(i) values (f.p) returning t.i"
PL/pgSQL function f(integer) line 3 at SQL statement
select * from t;
 i 
---
 1
(1 row)