The following code simulates a dirty read. The actual isolation level will be promoted to either read uncommitted or serializable. treats the IsolationLevel passed to BeginTransaction as a minimum level. If allowed, the same query could return different rows when executed twice in the same transaction. Phantoms are rows that get changed or added to meet the where clause of a query during a transaction. ![]() The results contain data that was never actually committed to the database.Ī nonrepeatable read occurs when a transaction queries the same row twice, but the results are different because it was changed between the two queries by another transaction. This level allows dirty reads, nonrepeatable reads, and phantoms:Ī dirty read occurs when changes pending in one transaction are returned by a query outside of the transaction, but the changes in the transaction are rolled back. ![]() SQLite also supports read uncommitted when using a shared cache. Other statements executed outside of the transaction aren't affected by the transaction's changes. This isolation level guarantees that any changes made within a transaction are completely isolated. Transactions are serializable by default in SQLite. Because of this, calls to BeginTransaction and the Execute methods on SqliteCommand may time out if another transaction takes too long to complete.įor more information about locking, retries, and timeouts, see Database errors. In SQLite, only one transaction is allowed to have changes pending in the database at a time. Using a transaction can also improve performance on SQLite when making numerous changes to the database at once. The initial state of the database when the transaction was started is preserved. If any statement in the transaction fails, changes made by the previous statements can be rolled back. ![]() Transactions let you group multiple SQL statements into a single unit of work that is committed to the database as one atomic unit.
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