Postgres: Why is the performance so bad on subselects with Offset/Limit

Question

Can you please help me understand the reason for the performance drop between these statements?

For me it seems like in case of D & E he is first joining the add

Answer 1

I think that the join expressed in the SELECT clause is being executed even for the 100000 rows you are not including in the final data set.

How about this:

SELECT s2.user_id,
(SELECT address_id FROM address a WHERE a.user_id = s2.user_id ORDER BY address_id OFFSET 0 LIMIT 1) AS a_id
FROM (select *
      from   subscribers s
      ORDER BY s.user_id
      OFFSET 100000 LIMIT 200) s2

Failing that, try a common table expression:

With s2 as (
  select *
  from   subscribers s
  ORDER BY s.user_id
  OFFSET 100000 LIMIT 200)
SELECT s2.user_id,
(SELECT address_id FROM address a WHERE a.user_id = s2.user_id ORDER BY address_id OFFSET 0 LIMIT 1) AS a_id
FROM s2