![]() 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. Typically my database code follows the format of: using (SqlConnection connection = new SqlConnection(".No changes can be made to the database except within a transaction. To associate the command with the transaction you'll need the following piece of code after each new command object created: cmd.Transaction = trans If this code were to be executed against SQL server or Oracle an exception would be thrown stating that all commands must be assigned the active transaction (if there is one). One thing I noticed, though, is that your command objects you've created are not associated with the transaction. Keep in mind though, disposing a transaction object will not explicitly close the underlying database connection. If the transaction has not been committed the transaction will be rolled back. If the transaction has been committed, nothing will be rolled back. (I like this method because the code is cleaner without try/catches everywhere - I only use try/catch when I can react accordingly) Remember, in almost all exception cases the objects in a using block will still be disposed, even if you don't catch the exception. In many cases with my work, if the transaction hits the end of a using statement without a commit it will roll it back without me coding an explicit try/catch. ![]() In this case, the catch block could be used to retry an operation with different parameters and such. In an unexpected error condition I would rather my data be left as is and not in a half-committed state, which is the point of a transaction. Transactions must be committed explicitly as Daniel said.What bothers me is WHY does it not make any difference wether OR NOT I use trans.Rollback() in the catch-block.Ģ.) I am using the "using(resource)"-statement so what will happen if the transaction succeeds/commits to the state of the connection ? Will it be closed? Just concern that I do not do use the `using(var trans = new SQLiteTransaction()) That is ok because I used a transaction and the. The connection from the transaction needs to be shared among the dataprovider methods.ġ.) When a SQLiteException occurs because of inserting same primary keys "John" there is not inserted any of the "John" values. SQLiteCommand cmd2 = con.CreateCommand() Ĭmd2.CommandText = "INSERT INTO TEST(Name) VALUES('John')" Īs I use SQLite its best practice to use the SQLiteTransaction class for every executed sql command. ![]() SQLiteCommand cmd1 = con.CreateCommand() Ĭmd1.CommandText = "INSERT INTO TEST(Name) VALUES('John')" Var con = new Source=A:\TransactionScopeTest\TransactionTest.db Foreign Keys=ON") ĭo 2 sqlite inserts with same Primary Key value to raise an exception Create the Connection Transaction: public SQLiteTransaction BeginTransaction()
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