Transaction Commit

The commit policies for implicit and explicit transactions are as follows:

1. Implicit transaction. A single DML/DDL statement can automatically trigger an implicit transaction, which does not have explicit transaction block control statements (such as START TRANSACTION/BEGIN/COMMIT/END). After a DML/DDL statement ends, the transaction is automatically committed.
2. Explicit transaction. An explicit transaction uses an explicit statement, such as START TRANSACTION or BEGIN, to control the start of the transaction. The COMMIT and END statements control the commit of a transaction.

   A subtransaction must exist in an explicit transaction or stored procedure. The SAVEPOINT statement controls the start of a subtransaction, and the RELEASE SAVEPOINT statement controls the end of a subtransaction. If a subtransaction is not released during transaction committing, commit the subtransaction first. The transaction is not committed until all subtransactions are committed.

   Ustore supports READ COMMITTED. At the beginning of statement execution, the current system CSN is obtained for querying the current statement. The visible result of the entire statement is determined at the beginning of statement execution and is not affected by subsequent transaction modifications. By default, READ COMMITTED in the Ustore is consistent. Ustore also supports standard 2PC transactions.