nhibernate - 如何在 nhibernate 中使用 ToFuture？

Question

假设我有这些问题

// Linq 
    var allRecords = session.Query<Table1P>().FetchMany(x => x.Table2).FetchMany(x => x.Table3).FetchMany(x => x.Table4).FetchMany(x => x.Table6).ToList();

// Hql
string hqlQuery = @"from Table1 tbl1
                                left join fetch tbl1.Table2 tbl2
                                left join fetch tbl1.Table3
                                left join fetch tbl1.Table4
                                left join fetch tbl1.Table6
                                left join fetch tbl2.Table5s";

在上述情况下，我需要执行所有这些连接以停止延迟加载并进行预加载。现在这会在 nhibernate 分析器中产生关于连接过多的警报。

http://nhprof.com/Learn/Alerts/TooManyJoins

因此，停止此警报的一种方法是分解连接。并进行多次查询。这就是我想要做的。然而与此同时，我一直在阅读有关 future 功能的信息，我认为它可以让我分解查询(以停止过多的连接)但仍然一次执行它。

编辑

我一直在尝试 ToFuture 并发现它在尝试限制要返回的数据量时速度较慢(如果我尝试恢复所有内容则它会更快，因为它不会崩溃)。

  var allRecords = session.Query<Table1P>().FetchMany(x => x.Table2).FetchMany(x => x.Table3).FetchMany(x => x.Table4).FetchMany(x => x.Table6).Take(3000).ToList();

// result (2.731 seconds), row count 3000, duration 8 ms/ 2013 ms

select TOP (3000 /* @p0 */) table1p0_.Id        as Id1_0_,
                 table2x1_.Id        as Id2_1_,
                 table3x2_.Id        as Id3_2_,
                 table4x3_.Id        as Id4_3_,
                 table6x4_.Id        as Id6_4_,
                 table1p0_.F1        as F2_1_0_,
                 table1p0_.F2        as F3_1_0_,
                 table1p0_.F3        as F4_1_0_,
                 table2x1_.F1        as F2_2_1_,
                 table2x1_.F2        as F3_2_1_,
                 table2x1_.F3        as F4_2_1_,
                 table2x1_.Table1_id as Table5_2_1_,
                 table2x1_.Table1_id as Table5_0__,
                 table2x1_.Id        as Id0__,
                 table3x2_.F1        as F2_3_2_,
                 table3x2_.F2        as F3_3_2_,
                 table3x2_.F3        as F4_3_2_,
                 table3x2_.Table1_id as Table5_3_2_,
                 table3x2_.Table1_id as Table5_1__,
                 table3x2_.Id        as Id1__,
                 table4x3_.F1        as F2_4_3_,
                 table4x3_.F2        as F3_4_3_,
                 table4x3_.F3        as F4_4_3_,
                 table4x3_.Table1_id as Table5_4_3_,
                 table4x3_.Table1_id as Table5_2__,
                 table4x3_.Id        as Id2__,
                 table6x4_.F1        as F2_6_4_,
                 table6x4_.F2        as F3_6_4_,
                 table6x4_.F3        as F4_6_4_,
                 table6x4_.Table1_id as Table5_6_4_,
                 table6x4_.Table1_id as Table5_3__,
                 table6x4_.Id        as Id3__
from   Table1 table1p0_
       left outer join [Table2] table2x1_
         on table1p0_.Id = table2x1_.Table1_id
       left outer join [Table3] table3x2_
         on table1p0_.Id = table3x2_.Table1_id
       left outer join [Table4] table4x3_
         on table1p0_.Id = table4x3_.Table1_id
       left outer join [Table6] table6x4_
         on table1p0_.Id = table6x4_.Table1_id

使用 future

// result (4.808 seconds), row count 6944 / 75/ 374, duration 1ms / 4022 ms

                // will load the Entities with Table2 fetched
                var allRecords = session.Query<Table1P>()
                    .FetchMany(x => x.Table2)
                    .ToFuture()
                    .Take(3000);

                // will load the Entities with Table3 fetched
                session.Query<Table1P>()
                    .FetchMany(x => x.Table3)
                    .ToFuture();

                // will load the Entities with Table4 fetched
                session.Query<Table1P>()
                    .FetchMany(x => x.Table4)
                    .ToFuture();

                // will load the Entities with Table6 fetched
                session.Query<Table1P>()
                    .FetchMany(x => x.Table6)
                    .ToFuture();

                // will trigger all queries at once and the session cache will make sure,
                // that the results of all queries fill the same Entities
                allRecords.ToList();


select table1p0_.Id        as Id1_0_,
       table2x1_.Id        as Id2_1_,
       table1p0_.F1        as F2_1_0_,
       table1p0_.F2        as F3_1_0_,
       table1p0_.F3        as F4_1_0_,
       table2x1_.F1        as F2_2_1_,
       table2x1_.F2        as F3_2_1_,
       table2x1_.F3        as F4_2_1_,
       table2x1_.Table1_id as Table5_2_1_,
       table2x1_.Table1_id as Table5_0__,
       table2x1_.Id        as Id0__
from   Table1 table1p0_
       left outer join [Table2] table2x1_
         on table1p0_.Id = table2x1_.Table1_id;



select table1p0_.Id        as Id1_0_,
       table3x1_.Id        as Id3_1_,
       table1p0_.F1        as F2_1_0_,
       table1p0_.F2        as F3_1_0_,
       table1p0_.F3        as F4_1_0_,
       table3x1_.F1        as F2_3_1_,
       table3x1_.F2        as F3_3_1_,
       table3x1_.F3        as F4_3_1_,
       table3x1_.Table1_id as Table5_3_1_,
       table3x1_.Table1_id as Table5_0__,
       table3x1_.Id        as Id0__
from   Table1 table1p0_
       left outer join [Table3] table3x1_
         on table1p0_.Id = table3x1_.Table1_id;



select table1p0_.Id        as Id1_0_,
       table4x1_.Id        as Id4_1_,
       table1p0_.F1        as F2_1_0_,
       table1p0_.F2        as F3_1_0_,
       table1p0_.F3        as F4_1_0_,
       table4x1_.F1        as F2_4_1_,
       table4x1_.F2        as F3_4_1_,
       table4x1_.F3        as F4_4_1_,
       table4x1_.Table1_id as Table5_4_1_,
       table4x1_.Table1_id as Table5_0__,
       table4x1_.Id        as Id0__
from   Table1 table1p0_
       left outer join [Table4] table4x1_
         on table1p0_.Id = table4x1_.Table1_id;



select table1p0_.Id        as Id1_0_,
       table6x1_.Id        as Id6_1_,
       table1p0_.F1        as F2_1_0_,
       table1p0_.F2        as F3_1_0_,
       table1p0_.F3        as F4_1_0_,
       table6x1_.F1        as F2_6_1_,
       table6x1_.F2        as F3_6_1_,
       table6x1_.F3        as F4_6_1_,
       table6x1_.Table1_id as Table5_6_1_,
       table6x1_.Table1_id as Table5_0__,
       table6x1_.Id        as Id0__
from   Table1 table1p0_
       left outer join [Table6] table6x1_
         on table1p0_.Id = table6x1_.Table1_id;

从 nhibernate 分析器中获取的查询和时间。通过使用其中一组代码运行一次测试来运行测试，记录结果，停止 .net 开发服务器，然后运行另一组代码。

表 1 - 6200 行表 2 - 744 行表 3 - 75 行表 4 - 374 行表 6 - 300 行

几乎表 1 对所有其他表都是一对多的。

Answer 1

// will load the Entities with Table2 fetched
var allRecords = session.Query<Table1P>()
    .FetchMany(x => x.Table2)
    .ToFuture();

// will load the Entities with Table3 fetched
session.Query<Table1P>()
    .FetchMany(x => x.Table3)
    .ToFuture();

// will load the Entities with Table4 fetched
session.Query<Table1P>()
    .FetchMany(x => x.Table4)
    .ToFuture();

// will load the Entities with Table6 fetched
session.Query<Table1P>()
    .FetchMany(x => x.Table6)
    .ToFuture();

// will trigger all queries at once and the session cache will make sure,
// that the results of all queries fill the same Entities
allRecords.ToList();

改变

       .ToFuture()
       .Take(3000);

到

       .Take(3000);
       .ToFuture()

更新:

// Hql
var allRecords = session.CreateQuery("from Table1 left join fetch tbl1.Table2")
    .ToFuture<Table1>();

...

奇怪的是，这比 big join 慢。我现在不能在这里测试。也许数据库中没有那么多行，多个结果集的开销大于扩展连接的开销。你能尝试在 db 中使用更多数据吗？