Nhibernate 添加查询选项

Question

我最近遇到了 Nhibernate 生成的 SQL 的性能问题，如

中所述

Nhibernate generate plain sql query instead of execution statement

我还发现了一个描述类似经历的链接，来自唯一的杰夫·阿特伍德 (Jeff Atwood)，网址为

http://legeronline.blogspot.ca/2009/03/evils-of-slow-paramaterized-query-plans.html

有人知道是否可以向 Nhibernate 添加“优化未知”选项吗？

Answer 1

这个例子有点详细:

public class OptionInterceptor: EmptyInterceptor
{
    public override SqlString OnPrepareStatement(SqlString sql)
    {
        var parameters = sql.GetParameters();
        var paramCount = parameters.Count();

        if (paramCount == 0)
            return sql;

        string optionString = " OPTION (OPTIMIZE FOR (";

        for (var i = 0; i < paramCount; i++)
        {
            var comma = i > 0 ? "," : string.Empty;
            optionString = optionString + comma + "@p" + i + " UNKNOWN";
        }

        optionString = optionString + "))";

        var builder = new SqlStringBuilder(sql);

        builder.Add(optionString);

        return builder.ToSqlString();
    }
}

然后在你的 session 工厂/初始化程序中:

configuration.ExposeConfiguration(x =>
    {
        x.SetInterceptor(new OptionInterceptor());
    });