Why PostgreSQL recursive view execution plan is so inefficient? - postgresql

Question

My app employs a multilevel hierarchical structure. There are many PL/pgSQL functions in the app that use the same type of selection: "select entities according to a list and all their child entities". I created a recursive view trying to avoid redundancy. The problem is, if i understand correctly, PostgreSQL (12.3, compiled by Visual C++ build 1914, 64-bit) selects all entities first and then it filters the records.
Here is a simplified example.
drop view if exists v;
drop table if exists t;
create table t
(
id int primary key,
parent_id int
);
insert into t (id, parent_id)
select s, (s - 1) * random()
from generate_series(1, 100000) as s;
create recursive view v (start_id, id, pid) as
select id, id, parent_id
from t
union all
select v.start_id, t.id, t.parent_id
from t
inner join v on v.id = t.parent_id;
explain (analyze)
select *
from v
where start_id = 10
order by start_id, id;
explain (analyze)
select *
from v
where start_id in (10, 11, 12, 20, 100)
order by start_id, id;
Is there a better solution? Any help is greatly appreciated.
Here is the query plan I got on my computer:
Sort (actual time=3809.581..3812.541 rows=29652 loops=1)
" Sort Key: v.start_id, v.id"
Sort Method: quicksort Memory: 2158kB
-> CTE Scan on v (actual time=0.044..3795.424 rows=29652 loops=1)
" Filter: (start_id = ANY ('{10,11,12,20,100}'::integer[]))"
Rows Removed by Filter: 1069171
CTE v
-> Recursive Union (actual time=0.028..3411.325 rows=1098823 loops=1)
-> Seq Scan on t (actual time=0.025..19.465 rows=100000 loops=1)
-> Merge Join (actual time=74.631..127.916 rows=41618 loops=24)
Merge Cond: (t_1.parent_id = v_1.id)
-> Sort (actual time=46.021..59.589 rows=99997 loops=24)
Sort Key: t_1.parent_id
Sort Method: external merge Disk: 1768kB
-> Seq Scan on t t_1 (actual time=0.016..11.797 rows=100000 loops=24)
-> Materialize (actual time=23.542..42.088 rows=65212 loops=24)
-> Sort (actual time=23.188..29.740 rows=45385 loops=24)
Sort Key: v_1.id
Sort Method: quicksort Memory: 25kB
-> WorkTable Scan on v v_1 (actual time=0.017..7.412 rows=45784 loops=24)
Planning Time: 0.260 ms
Execution Time: 3819.152 ms