Optimistic Locking in DatabaseDatabase
Databases are computer systems designed for storing data.
This note serves as a link to connect database-related notes.
ACID
[[Optimistic Locking]]/Pessimistic LockingPessimistic Locking
Pessimistic Locking in [[Database]] systems is a locking mechanism that relies on exclusive locks to ensure two transactions don't update rows at the same time.
For example:
user A fetches acco...
Status: #🌱... systems is a locking mechanism that relies on data versions to stop updates based on stale data.
For example:
- user A fetches account data which says
amount: 100, version: 1 - user B fetches the same row, getting
amount: 100, version: 1 - user B updates the row remove 100, succeeds and updates the record to
amount: 0, version: 2 - user A tries to remove 10 more, but their update fails because they were trying to update based on version 1, which is not the current version anymore
Optimistic locking is non-blocking - if the "locked" key was changed, the transaction will fail, will be reverted (ACID) and retried.
If the cost of retrying a transaction is too high, Pessimistic LockingPessimistic Locking
Pessimistic Locking in [[Database]] systems is a locking mechanism that relies on exclusive locks to ensure two transactions don't update rows at the same time.
For example:
user A fetches acco... should be preferred.
Status: #🌱
References:
- https://vladmihalcea.com/optimistic-vs-pessimistic-locking/