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1. #Sqlite transaction rollback how to
2. #Sqlite transaction rollback update
3. #Sqlite transaction rollback upgrade
4. #Sqlite transaction rollback code

#Sqlite transaction rollback how to

Transaction.Summary: in this tutorial, you will learn how to use the SQLite full-text search feature by using the FTS5 virtual table module. Commit savepoint and continue with the transaction Transaction.Rollback("optimistic-update")

#Sqlite transaction rollback update

Concurrent update detected! Rollback savepoint and retry Var recordsAffected = updateCommand.ExecuteNonQuery() Var updateCommand = connection.CreateCommand() VALUES (datetime('now'), 'User updates data with id 1') Var insertCommand = connection.CreateCommand() Transaction may include additional statements before the savepoint using (var transaction = connection.BeginTransaction())

#Sqlite transaction rollback code

The following code illustrates using the Optimistic Offline Lock pattern to detect concurrent updates and resolve conflicts within a savepoint as part of a larger transaction. Savepoints can be rolled back without affecting other parts of the transaction, and even though a savepoint may be committed (released), its changes may later be rolled back as part of its parent transaction. Savepoints can be used to create nested transactions. When this happens, the application will need to retry the entire transaction. After the first write statement, both concurrent reads and writes are blockedĬommands inside a deferred transaction can fail if they cause the transaction to be upgraded from a read transaction to a write transaction while the database is locked. Var writeCommand = connection.CreateCommand() After a the first read statement, concurrent writes are blocked until the Var value = (long)readCommand.ExecuteScalar() Var readCommand = connection.CreateCommand() Before the first statement of the transaction is executed, both concurrent using (var transaction = connection.BeginTransaction(deferred: true))

This can be useful for enabling concurrent access to the database during the transaction.

#Sqlite transaction rollback upgrade

It also causes the transaction to gradually upgrade from a read transaction to a write transaction as needed by its commands. This defers the creation of the actual transaction in the database until the first command is executed. Starting with version 5.0, transactions can be deferred. Var value = (string)quer圜ommand.ExecuteScalar() Var quer圜ommand = secondConnection.CreateCommand() Using (secondConnection.BeginTransaction(IsolationLevel.ReadUncommitted)) while the transaction on the first connection is active Without ReadUncommitted, the command will time out since the table is locked Var updateCommand = firstConnection.CreateCommand() using (var firstTransaction = firstConnection.BeginTransaction()) Note, the connection string must include Cache=Shared. 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.