InnoDB / MySQL - new transaction uses old data on SELECT instead of returning updated data

问题

1. Begin transaction Tx1
2. Tx1 performs a SELECT
3. Commit Tx1
4. Begin transaction Tx2 in a different session, using a different connection
5. Tx2 performs a SELECT
6. Update rows in Tx2
7. Commit Tx2
8. Begin a new transaction, Tx1
9. Perform select - get results from step 2(??)
10. Commit Tx1
11. Begin transaction Tx1
12. Perform select - get CORRECT results, i.e. the committed updates from Tx2

Very confused... How can this happen? It is happening reliably and consistently.

回答1:

Turns out this can happen if the transaction isolation level is set to REPEATABLE READ. Set the transaction isolation level to READ COMMITTED and everything is hunky dory. Doesn't really explain why (must be some sort of BEGIN TRANSACTION hanging around?)

来源：https://stackoverflow.com/questions/21613500/innodb-mysql-new-transaction-uses-old-data-on-select-instead-of-returning-up