How to Resolve Stale Data Selection in MySQL After Delete and Insert Operations?

MySQL: Recovering from Stale Data Selection after Delete and Insert

In multiple-threaded WSGI web applications using MySQL, session management can occasionally encounter inconsistencies, where deleted sessions are still returned in select queries.

This behavior stems from MySQL's default isolation level, "REPEATABLE READ." This level ensures that transactions remain unaffected by changes made after their initiation, regardless of whether those changes have been committed. Thus, other connections continue to retrieve old session data even after a new session has been inserted.

To resolve this issue, consider the following:

• End the Transaction: Issue COMMIT or ROLLBACK commands in the affected sessions to conclude the persistent transactions and allow them to observe the most recent database state.
• Modify Isolation Level: Change the isolation level to "READ COMMITTED" for the affected sessions. This level allows newly committed data to be visible to subsequent queries within the same transaction.

By implementing either approach, the connections should no longer select outdated data and will reflect the database's current state.

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