query optimization

Question

I have 50964218 records in a table. I am going to fetch the data from this table and insert into the same table. Which takes more time to manipulate. How optimize this query.

The Query is

INSERT INTO contacts_lists (contact_id, list_id, is_excluded, added_by_search)
SELECT contact_id, 68114 , TRUE, added_by_search
FROM contacts_lists cl1
WHERE list_id = 67579
AND is_excluded = TRUE
AND NOT EXISTS 
    (SELECT 1 FROM contacts_lists cl2 
     WHERE cl1.contact_id = cl2.contact_id AND cl2.list_id = 68114 )

index: list_id,contact_id

Answer 1

you will probably get better results with a left join:

select t1.[field], ...
from t1
left join t2
on [conditions]
where t2.[any pkey field] is null;