--create base table
Create table myt(
a int,
b int);

--create child table
Create table myt_d( check (a>10)) inherits(myt);

-- Trigger function which will divert insert into particular partition table
create or replace function insert_myt_trigger_func()
returns trigger as $$
	declare
	vsql text;
	begin
		IF (new.a >10) THEN
		  vSql := 'insert into myt_d  values('||new.a||','||new.b||')';
		  execute vSql;
		ELSE
		  RAISE EXCEPTION 'column value for a out of range. Fix insert_my_trigger_func() function!';
		END IF; 
		return null;
	end;
$$
language plpgsql;

--trigger for insert..redirect from base to child
create trigger insert_myt_trigger
	before insert on myt
for each row execute procedure insert_myt_trigger_func();

--should fail
insert into myt values(10,10);

--should be successfully inserted
insert into myt values(11,11);

begin work;
select count(*) from myt where a>10;

--get oid of base and child tables
select oid from pg_class where relname='myt_d' or relname='myt';
--check if both of them are locked
select locktype, relation, mode from pg_locks;



pg=# select oid from pg_class where relname='myt_d' or relname='myt';
  oid   
--------
 271078
 271081
(2 rows)

pg=# select locktype, relation, mode from pg_locks;
  locktype  | relation |      mode       
------------+----------+-----------------
 virtualxid |          | ExclusiveLock
 relation   |   271081 | AccessShareLock
 virtualxid |          | ExclusiveLock
 relation   |   271078 | AccessShareLock
 relation   |    11001 | AccessShareLock
(5 rows)

pg=#