The sqlite3_blob finishes when it is closed. An open sqlite3_blob used for incremental BLOB I/O counts as an unfinished statement. A statement finishes when its prepared statement is reset or finalized.
After a BEGIN EXCLUSIVE, no other database connection except for read_uncommitted connections will be able to read the database and no other connection without exception will be able to write the database until the transaction is complete.Īn implicit transaction (a transaction that is started automatically, not a transaction started by BEGIN) is committed automatically when the last active statement finishes. An exclusive transaction causes EXCLUSIVE locks to be acquired on all databases. Other processes can continue to read from the database, however. After a BEGIN IMMEDIATE, no other database connection will be able to write to the database or do a BEGIN IMMEDIATE or BEGIN EXCLUSIVE. If the transaction is immediate, then RESERVED locks are acquired on all databases as soon as the BEGIN command is executed, without waiting for the database to be used.
Because the acquisition of locks is deferred until they are needed, it is possible that another thread or process could create a separate transaction and write to the database after the BEGIN on the current thread has executed. The first read operation against a database creates a SHARED lock and the first write operation creates a RESERVED lock. Locks are not acquired until the first read or write operation. Thus with a deferred transaction, the BEGIN statement itself does nothing to the filesystem. Deferred means that no locks are acquired on the database until the database is first accessed. The default transaction behavior is deferred. Transactions can be deferred, immediate, or exclusive. The COMMIT command and the ROLLBACK command without the TO clause work the same on SAVEPOINT transactions as they do with transactions started by BEGIN. An attempt to invoke the BEGIN command within a transaction will fail with an error, regardless of whether the transaction was started by SAVEPOINT or a prior BEGIN. The "TO SAVEPOINT name" clause of the ROLLBACK command shown in the syntax diagram above is only applicable to SAVEPOINT transactions. For nested transactions, use the SAVEPOINT and RELEASE commands. Transactions created using BEGIN.COMMIT do not nest. See the documentation on the ON CONFLICT clause for additional information about the ROLLBACK conflict resolution algorithm. But a transaction will also ROLLBACK if the database is closed or if an error occurs and the ROLLBACK conflict resolution algorithm is specified. Such transactions usually persist until the next COMMIT or ROLLBACK command. Transactions can be started manually using the BEGIN command. Automatically started transactions are committed when the last query finishes. Any command that changes the database (basically, any SQL command other than SELECT) will automatically start a transaction if one is not already in effect. SqlClient supports it.No changes can be made to the database except within a transaction. If a provider does not implement support for System.Transactions, it is possible that calls to these APIs will be completely ignored. when disposed if either commands failsĮF Core relies on database providers to implement support for System.Transactions. Commit transaction if all commands succeed, transaction will auto-rollback The following example shows two SaveChanges operations and a LINQ query being executed in a single transaction: using var context = new BloggingContext() You can use the DbContext.Database API to begin, commit, and rollback transactions. You should only manually control transactions if your application requirements deem it necessary. This means that SaveChanges is guaranteed to either completely succeed, or leave the database unmodified if an error occurs.įor most applications, this default behavior is sufficient. If any of the changes fail, then the transaction is rolled back and none of the changes are applied to the database. Default transaction behaviorīy default, if the database provider supports transactions, all changes in a single call to SaveChanges are applied in a transaction. You can view this article's sample on GitHub.
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