ServiceStack OrmLite Select 带更新锁

Question

我有以下代码：

protected static void InsertOrUpdate<T>(
    IDbConnection connection,
    T item,
    Expression<Func<T, bool>> singleItemPredicate,
    Expression<Func<T, object>> updateOnlyFields = null)
{
    var type = item.GetType();
    var idProperty = type.GetProperty("Id");
    var currentId = (int)idProperty.GetValue(item);
    if (currentId != 0)
    {
        throw new ApplicationException("Cannot insert or update with non-zero ID");
    }

    var existingItem = connection.Select(singleItemPredicate).SingleOrDefault();
    if (existingItem == null)
    {
        Insert(connection, item);
        return;
    }

    var existingId = (int)idProperty.GetValue(existingItem);
    idProperty.SetValue(item, existingId);

    var affectedRowCount = connection.UpdateOnly(item, onlyFields: updateOnlyFields, where: singleItemPredicate);
    if (affectedRowCount != 1)
    {
        throw new ApplicationException("Update failed");
    }
}

但是使用默认隔离级别，这可能会导致多个线程在同一个 table 上工作时出错。

我想要的是 select-row 来指定我想要更新锁，例如：

var existingItem = connection.Select(singleItemPredicate).WithUpdateLock().SingleOrDefault();

对于SQL服务器，这将在末尾添加WITH UPDLOCK SELECT行

我如何在 ServiceStack OrmLite 中最好地解决这个问题？

Answer 1

您可以使用 new SqlExpression SQL Filter just added in v4.5.5 that's now (available on MyGet) 自定义生成的 SQL 然后执行自定义的 Typed SqlExpression，例如：

var q = connection.From<T>()
    .Where(singleItemPredicate)
    .WithSqlFilter(sql => sql + " WITH UPDLOCK");

var existingItem = connection.Select(q).SingleOrDefault();
if (existingItem == null)
{
    connection.Insert(item);
    return;
}

ServiceStack OrmLite Select 带更新锁

ServiceStack OrmLite Select with update lock

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