Transaction levels
Better specify needed transaction levels Especially posting of questionanswers have been changed as these error anyhow in case 2 new entries are made at the same time (due to primary key constraints)
Transaction basics:
- post something (like assignment + file): READ COMMITTED
- patch something: REPEATABLE READ
- create/update something: REPEATABLE READ (will lock if exists, will fail is not exists and created in the mean time by 2 transactions)
- mainly teacher-actions, when things need t not exist before transaction (like review distribution): SERIALIZABLE
Edited by Yorick de Vries