如何使用Nhibernate和Sybase实施限制 [英] How to implement limit with Nhibernate and Sybase

问题描述

我们使用Nhibernate 3.3连接到我们的Sybase Ase 15数据库.除了不支持该限制(或最高限制)以外，其他一切都很好.它在sybase中实现，但不在Nhibernate中实现. 你有解决办法吗?

We use Nhibernate 3.3 to connect to our Sybase Ase 15 database. Everything is fine except for the non support of the limit (or top). It is implemented in sybase but not in Nhibernate. Do you have a solution?

我尝试创建一个CustomSybaseAse15Dialect，在其中进行以下更改:

I tried to create a CustomSybaseAse15Dialect where I change this:

     public override bool SupportsLimitOffset
{
    get { return true; }
}

public override SqlString GetLimitString(SqlString sql, SqlString offset, SqlString limit)
{    
    int insertionPoint = GetAfterSelectInsertPoint(sql);

    if (insertionPoint > 0)
    {
        SqlStringBuilder limitBuilder = new SqlStringBuilder();
        limitBuilder.Add("select");
        if (insertionPoint > 6)
        {
            limitBuilder.Add(" distinct ");
        }
        limitBuilder.Add(" top ");
        limitBuilder.Add(limit);
        if (offset != null)
        {
            limitBuilder.Add(" start at ");
            limitBuilder.Add(offset);
        }
        limitBuilder.Add(sql.Substring(insertionPoint));
        return limitBuilder.ToSqlString();
    }
    else
    {
        return sql; // unchanged
    }
}

/// <summary>
/// Copied from MsSql2000Dialect.
/// </summary>
private int GetAfterSelectInsertPoint(SqlString sql)
{
    if (sql.StartsWithCaseInsensitive("select distinct"))
    {
        return 15;
    }
    if (sql.StartsWithCaseInsensitive("select"))
    {
        return 6;
    }
    throw new NotSupportedException("The query should start with 'SELECT' or 'SELECT DISTINCT'");
}

使用Linq2Nhibernate语法，它可以很好地与

Using the Linq2Nhibernate syntax, it works good with

Session.Query<product>().First()

限制已正确设置为1，但如果我这样做

limit is correctly set to 1 but if I do this

Session.Query<product>().Take(3).ToList()

限制设置为?".

我该怎么办?

推荐答案

nHibernate中存在一个错误.它已经修复，但尚未包含在正式版本中.

as mentioned in the previous comment there is a bug in nHibernate. It is already fixed but not yet included in an official version.

https://nhibernate.jira.com/browse/NH-3281

您可以从 https://github.com/nhibernate/下载主要源代码并手动构建dll. nhibernate-core .

迈克尔

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