mysql - Speeding up slow update query -

i trying update field based on table's field using join:

update transactions join products on products.link = transactions.product_id  set transactions.user_id = products.user_id transactions.user_id != products.user_id 

however, taking long time (over 15 minutes). products has 10k rows, transactions has 90k rows. there anyway can optimize query?

transactions table:

id              int(11) transaction_id  varchar(255) user_id         int(11) product_id      varchar(50) 

products table:

id      int(11) user_id int(11) link    varchar(45) 

i not sure if sql can help. can try?

update transactions t1     inner join ( select t2.id , p.user_id               transactions t2, projects p               t2.product_id = p.link                 , t2.user_id != p.user_id              ) t3 on t1.id = t3.id set t1.user_id = t3.user_id