Issue with inserting values that fetched from locked rows - mysql

Question

I have two scripts bounded by transactions:
The first:
START TRANSACTION;
update product set price = 70;
SELECT SLEEP(20);
rollback;
The second:
START TRANSACTION;
insert into product_order(product_id, amount, price) select id, amount, price from product;
commit;
The second transaction has started execute when the first one is in 'sleep' state.
So, I expected that second one will have executed during sleeping of the first transaction.
Unexpectedly the second transaction is waiting until the first one goes out from sleep state.
I know that it is something connected to row locking. But I hadn't updated the rows that included into the first transaction.
My question: What is the reason of such behaviour and how I can get rid of it?

Answer 1

It look like the lock will be released after the end of the transaction (You can't read the data because if the transaction fails the database will have to rollback to the previous state)
Before your insert you should set the sessions transaction isolation level so it can read data that are not commited:
SET SESSION TRANSACTION ISOLATION LEVEL READ UNCOMMITTED;
START TRANSACTION;
insert into product_order(product_id, amount, price) select id, amount, price from product;
COMMIT;
SET SESSION TRANSACTION ISOLATION LEVEL REPEATABLE READ;