Isolation levels
Two doctors each check that someone else is on call, set only their own row to off call, and commit. Which isolation level catches it?
Seven pieces of work touch the same ward records at once on one machine, in a fixed order you step through. Each tab replays that same order under a different rule for what one open transaction may see of another's. Watch the race counter climb, and watch the line that says whether a doctor is still on call.
Board: Transactions →Thirty-two fixed operations across seven transactions on one machine. Step through them one at a time.
try this Pick You see the database as it was when you began, press Play next operation to the end, and watch races permitted.
Included with a plan
This lab is included with a plan. The first three lessons of every track are free, with their boards and videos. A plan unlocks every lesson, board, video, lab and paper for one price.
see also Spanner: Google's Globally-Distributed Database, Large-scale Incremental Processing Using Distributed Transactions and Notifications and A Critique of ANSI SQL Isolation Levels in Papers.