[gnome-db] isolation level for transactions

[Rodrigo Moya <rodrigo gnome-db org>]

Hi

I've just added two new methods to GdaTransaction:

typedef enum {
	GDA_TRANSACTION_ISOLATION_UNKNOWN,
	GDA_TRANSACTION_ISOLATION_READ_COMMITTED,
	GDA_TRANSACTION_ISOLATION_READ_UNCOMMITTED,
	GDA_TRANSACTION_ISOLATION_REPEATABLE_READ,
	GDA_TRANSACTION_ISOLATION_SERIALIZABLE
} GdaTransactionIsolation;

GdaTransactionIsolation gda_transaction_get_isolation_level
(GdaTransaction *xaction);
void                    gda_transaction_set_isolation_level
(GdaTransaction *xaction,
							     GdaTransactionIsolation level);

so, now, when providers get a GdaTransaction in the begin_transaction
method, they have to check the isolation level of the transaction, and
act accordingly (of course, if they support this, if not, they can just
ignore it). For an example, here's how mysql does it:

static gboolean
gda_mysql_provider_begin_transaction (GdaServerProvider *provider,
				      GdaConnection *cnc,
				      GdaTransaction *xaction)
{
	MYSQL *mysql;
	gint rc;
	GdaMysqlProvider *myprv = (GdaMysqlProvider *) provider;

	g_return_val_if_fail (GDA_IS_MYSQL_PROVIDER (myprv), FALSE);
	g_return_val_if_fail (GDA_IS_CONNECTION (cnc), FALSE);
	g_return_val_if_fail (GDA_IS_TRANSACTION (xaction), FALSE);

	mysql = g_object_get_data (G_OBJECT (cnc), OBJECT_DATA_MYSQL_HANDLE);
	if (!mysql) {
		gda_connection_add_error_string (cnc, _("Invalid MYSQL handle"));
		return FALSE;
	}

	/* set isolation level */
	switch (gda_transaction_get_isolation_level (xaction)) {
	case GDA_TRANSACTION_ISOLATION_READ_COMMITTED :
		rc = mysql_real_query (mysql, "SET TRANSACTION ISOLATION LEVEL READ
COMMITTED", 46);
		break;
	case GDA_TRANSACTION_ISOLATION_READ_UNCOMMITTED :
		rc = mysql_real_query (mysql, "SET TRANSACTION ISOLATION LEVEL READ
UNCOMMITTED", 48);
		break;
	case GDA_TRANSACTION_ISOLATION_REPEATABLE_READ :
		rc = mysql_real_query (mysql, "SET TRANSACTION ISOLATION LEVEL
REPEATABLE READ", 47);
		break;
	case GDA_TRANSACTION_ISOLATION_SERIALIZABLE :
		rc = mysql_real_query (mysql, "SET TRANSACTION ISOLATION LEVEL
SERIALIZABLE", 44);
		break;
	default :
		rc = 0;
	}

	if (rc != 0) {
		gda_connection_add_error (cnc, gda_mysql_make_error (mysql));
		return FALSE;
	}

	/* start the transaction */
	rc = mysql_real_query (mysql, "BEGIN", strlen ("BEGIN"));
	if (rc != 0) {
		gda_connection_add_error (cnc, gda_mysql_make_error (mysql));
		return FALSE;
	}

	return TRUE;
}

please, people working on the providers, take this into account.

cheers