We have 3 tables: COPY, PHYSICAL_COPY  and COPY_CLASSIFICATION. The
last two all linked to COPY using foreign keys: PHYSICAL_COPY.COPY_ID
-> COPY.ID and COPY_CLASSIFICATION.COPY_ID to COPY.ID

We have the following query which returns an empty result set because
the sub-query with alias "a" returns an empty result set

select *
from
(
    -- This sub-query returns empty result in 0.047 s
    SELECT * FROM PHYSICAL_COPY WHERE (PHYSICAL_COPY."REPOSITORY_TYPE" = 'blah')
) a
INNER JOIN COPY_CLASSIFICATION ON a."COPY_ID" = COPY_CLASSIFICATION."COPY_ID"
INNER JOIN COPY ON COPY_CLASSIFICATION.COPY_ID = COPY."ID";

This query with 2 joins takes 0.8 s. However, commenting out either
join brings this down to 0.047s.

How can we optimize this query so that it runs fast with both joins in place?

Thanks,

Alec