/********************************************************
* ADO.NET 2.0 Data Provider for SQLite Version 3.X
* Written by Robert Simpson (robert@blackcastlesoft.com)
*
* Released to the public domain, use at your own risk!
********************************************************/
namespace System.Data.SQLite
{
using System;
using System.Collections.Generic;
using System.Data;
using System.Data.Common;
using System.Threading;
///////////////////////////////////////////////////////////////////////////////////////////////
/// <summary>
/// SQLite implementation of DbTransaction.
/// </summary>
public sealed class SQLiteTransaction : DbTransaction
{
/// <summary>
/// The connection to which this transaction is bound
/// </summary>
internal SQLiteConnection _cnn;
/// <summary>
/// Matches the version of the connection.
/// </summary>
private int _version;
/// <summary>
/// The isolation level for this transaction.
/// </summary>
private IsolationLevel _level;
/// <summary>
/// The original transaction level for the associated connection
/// when this transaction was created (i.e. begun).
/// </summary>
private int _beginLevel;
/// <summary>
/// The SAVEPOINT name for this transaction, if any. This will
/// only be non-null if this transaction is a nested one.
/// </summary>
private string _savePointName;
///////////////////////////////////////////////////////////////////////////////////////////////
/// <summary>
/// Constructs the transaction object, binding it to the supplied connection
/// </summary>
/// <param name="connection">The connection to open a transaction on</param>
/// <param name="deferredLock">TRUE to defer the writelock, or FALSE to lock immediately</param>
internal SQLiteTransaction(SQLiteConnection connection, bool deferredLock)
{
_cnn = connection;
_version = _cnn._version;
_level = (deferredLock == true) ?
SQLiteConnection.DeferredIsolationLevel :
SQLiteConnection.ImmediateIsolationLevel;
int transactionLevel;
if ((transactionLevel = _cnn._transactionLevel++) == 0)
{
try
{
using (SQLiteCommand cmd = _cnn.CreateCommand())
{
if (!deferredLock)
cmd.CommandText = "BEGIN IMMEDIATE;";
else
cmd.CommandText = "BEGIN;";
cmd.ExecuteNonQuery();
_beginLevel = transactionLevel;
}
}
catch (SQLiteException)
{
_cnn._transactionLevel--;
_cnn = null;
throw;
}
}
else
{
try
{
using (SQLiteCommand cmd = _cnn.CreateCommand())
{
_savePointName = GetSavePointName();
cmd.CommandText = String.Format(
"SAVEPOINT {0};", _savePointName);
cmd.ExecuteNonQuery();
_beginLevel = transactionLevel;
}
}
catch (SQLiteException)
{
_cnn._transactionLevel--;
_cnn = null;
throw;
}
}
}
///////////////////////////////////////////////////////////////////////////////////////////////
#region IDisposable "Pattern" Members
private bool disposed;
private void CheckDisposed() /* throw */
{
#if THROW_ON_DISPOSED
if (disposed)
throw new ObjectDisposedException(typeof(SQLiteTransaction).Name);
#endif
}
///////////////////////////////////////////////////////////////////////////////////////////////
/// <summary>
/// Disposes the transaction. If it is currently active, any changes are rolled back.
/// </summary>
protected override void Dispose(bool disposing)
{
try
{
if (!disposed)
{
if (disposing)
{
////////////////////////////////////
// dispose managed resources here...
////////////////////////////////////
if (IsValid(false))
{
IssueRollback(false);
}
}
//////////////////////////////////////
// release unmanaged resources here...
//////////////////////////////////////
}
}
finally
{
base.Dispose(disposing);
//
// NOTE: Everything should be fully disposed at this point.
//
disposed = true;
}
}
#endregion
///////////////////////////////////////////////////////////////////////////////////////////////
/// <summary>
/// Commits the current transaction.
/// </summary>
public override void Commit()
{
CheckDisposed();
SQLiteConnection.Check(_cnn);
IsValid(true);
if (_beginLevel == 0)
{
using (SQLiteCommand cmd = _cnn.CreateCommand())
{
cmd.CommandText = "COMMIT;";
cmd.ExecuteNonQuery();
}
_cnn._transactionLevel = 0;
_cnn = null;
}
else
{
using (SQLiteCommand cmd = _cnn.CreateCommand())
{
if (String.IsNullOrEmpty(_savePointName))
throw new SQLiteException("Cannot commit, unknown SAVEPOINT");
cmd.CommandText = String.Format(
"RELEASE {0};", _savePointName);
cmd.ExecuteNonQuery();
}
_cnn._transactionLevel--;
_cnn = null;
}
}
///////////////////////////////////////////////////////////////////////////////////////////////
/// <summary>
/// Returns the underlying connection to which this transaction applies.
/// </summary>
public new SQLiteConnection Connection
{
get { CheckDisposed(); return _cnn; }
}
///////////////////////////////////////////////////////////////////////////////////////////////
/// <summary>
/// Forwards to the local Connection property
/// </summary>
protected override DbConnection DbConnection
{
get { return Connection; }
}
///////////////////////////////////////////////////////////////////////////////////////////////
/// <summary>
/// Gets the isolation level of the transaction. SQLite only supports Serializable transactions.
/// </summary>
public override IsolationLevel IsolationLevel
{
get { CheckDisposed(); return _level; }
}
///////////////////////////////////////////////////////////////////////////////////////////////
/// <summary>
/// Rolls back the active transaction.
/// </summary>
public override void Rollback()
{
CheckDisposed();
SQLiteConnection.Check(_cnn);
IsValid(true);
IssueRollback(true);
}
///////////////////////////////////////////////////////////////////////////////////////////////
/// <summary>
/// Issue a ROLLBACK command against the database connection,
/// optionally re-throwing any caught exception.
/// </summary>
/// <param name="throwError">
/// Non-zero to re-throw caught exceptions.
/// </param>
private void IssueRollback(bool throwError)
{
SQLiteConnection cnn = Interlocked.Exchange(ref _cnn, null);
if (cnn != null)
{
if (_beginLevel == 0)
{
try
{
using (SQLiteCommand cmd = cnn.CreateCommand())
{
cmd.CommandText = "ROLLBACK;";
cmd.ExecuteNonQuery();
}
cnn._transactionLevel = 0;
}
catch
{
if (throwError)
throw;
}
}
else
{
try
{
using (SQLiteCommand cmd = cnn.CreateCommand())
{
if (String.IsNullOrEmpty(_savePointName))
throw new SQLiteException("Cannot rollback, unknown SAVEPOINT");
cmd.CommandText = String.Format(
"ROLLBACK TO {0};", _savePointName);
cmd.ExecuteNonQuery();
}
cnn._transactionLevel--;
}
catch
{
if (throwError)
throw;
}
}
}
}
///////////////////////////////////////////////////////////////////////////////////////////////
/// <summary>
/// Constructs the name of a new savepoint for this transaction. It
/// should only be called from the constructor of this class.
/// </summary>
/// <returns>
/// The name of the new savepoint -OR- null if it cannot be constructed.
/// </returns>
private string GetSavePointName()
{
int sequence = ++_cnn._transactionSequence;
return String.Format(
"sqlite_dotnet_savepoint_{0}", sequence);
}
///////////////////////////////////////////////////////////////////////////////////////////////
/// <summary>
/// Checks the state of this transaction, optionally throwing an exception if a state inconsistency is found.
/// </summary>
/// <param name="throwError">
/// Non-zero to throw an exception if a state inconsistency is found.
/// </param>
/// <returns>
/// Non-zero if this transaction is valid; otherwise, false.
/// </returns>
internal bool IsValid(bool throwError)
{
if (_cnn == null)
{
if (throwError == true) throw new ArgumentNullException("No connection associated with this transaction");
else return false;
}
if (_cnn._version != _version)
{
if (throwError == true) throw new SQLiteException("The connection was closed and re-opened, changes were already rolled back");
else return false;
}
if (_cnn.State != ConnectionState.Open)
{
if (throwError == true) throw new SQLiteException("Connection was closed");
else return false;
}
if (_cnn._transactionLevel == 0 || _cnn._sql.AutoCommit == true)
{
_cnn._transactionLevel = 0; // Make sure the transaction level is reset before returning
if (throwError == true) throw new SQLiteException("No transaction is active on this connection");
else return false;
}
return true;
}
}
}