将 SQL 转换为 QueryOver 以使用 group bys 获取行数

Question

我有以下 NHibernate QueryOver 查询：

var query = session.QueryOver<IssuanceReportLogEntity>()
                        .Where(i => i.CustomerId == customer.Id && i.RollbackIssuanceId == null);

if (Parms.StartDate != null) query.Where(i => i.IssuanceDateCreated >= Parms.StartDate);
if (Parms.EndDate != null) query.Where(i => i.IssuanceDateCreated <= Parms.EndDate);
if (Parms.GroupId != null) query.Where(i => i.RecipientGroupId == Parms.GroupId);
if (Parms.ProgramId != null) query.Where(i => i.ProgramId == Parms.ProgramId);

query.Select(
    Projections.Group<IssuanceReportLogEntity>(x => x.RecipientGroupId).WithAlias(() => receiver.RecipientGroupId),
    Projections.Group<IssuanceReportLogEntity>(x => x.RecipientId).WithAlias(() => receiver.RecipientId),
    Projections.Group<IssuanceReportLogEntity>(x => x.RecipientFullName).WithAlias(() => receiver.RecipientFullName),
    Projections.Group<IssuanceReportLogEntity>(x => x.RecipientEmployeeNumber).WithAlias(() => receiver.RecipientEmployeeNumber),
    Projections.Group<IssuanceReportLogEntity>(x => x.RecipientTitle).WithAlias(() => receiver.RecipientTitle),
    Projections.Count<IssuanceReportLogEntity>(x=>x.RecipientGroupId).WithAlias(()=>receiver.RecognitionTotalReceived),
    Projections.Sum<IssuanceReportLogEntity>(x=>x.Points).WithAlias(()=>receiver.TotalPoints));

if (customer.Settings.PointsEnabled)
{
    query.OrderBy(Projections.Sum<IssuanceReportLogEntity>(x => x.Points)).Desc();
}
else
{
    query.OrderBy(Projections.Count<IssuanceReportLogEntity>(x => x.InitiatorId)).Desc();
}

query.TransformUsing(Transformers.AliasToBean<TopReceiver>());

这会生成以下查询（对于数据的选择是正确的）：

SELECT TOP (20 /* @p0 */) this_.RecipientGroupId        as y0_,
               this_.RecipientId             as y1_,
               this_.RecipientFullName       as y2_,
               this_.RecipientEmployeeNumber as y3_,
               this_.RecipientTitle          as y4_,
               count(this_.RecipientGroupId) as y5_,
               sum(this_.Points)             as y6_
FROM   [IssuanceReportLog] this_
WHERE  (this_.CustomerId = '30a678bc-264a-4a04-aac4-a3270158929f' /* @p1 */
      and this_.RollbackIssuanceId is null)
     and this_.RecipientGroupId = '2fd9ec20-e870-42f6-b345-a3270158992a' /* @p2 */
GROUP  BY this_.RecipientGroupId,
        this_.RecipientId,
        this_.RecipientFullName,
        this_.RecipientEmployeeNumber,
        this_.RecipientTitle
ORDER  BY sum(this_.Points) desc

我需要做的是弄清楚如何让 NHibernate 在不删除 Group By 的情况下生成行计数，本质上是做类似的事情（注意前面的查询本质上是一个没有 TOP 的子查询）：

SELECT COUNT(*) FROM (
SELECT this_.RecipientGroupId        as y0_,
                 this_.RecipientId             as y1_,
                 this_.RecipientFullName       as y2_,
                 this_.RecipientEmployeeNumber as y3_,
                 this_.RecipientTitle          as y4_,
                 count(this_.RecipientGroupId) as y5_,
                 sum(this_.Points)             as y6_
FROM   [IssuanceReportLog] this_
WHERE  (this_.CustomerId = '30a678bc-264a-4a04-aac4-a3270158929f' /* @p1 */
        and this_.RollbackIssuanceId is null)
       and this_.RecipientGroupId = '2fd9ec20-e870-42f6-b345-a3270158992a' /* @p2 */
GROUP  BY this_.RecipientGroupId,
          this_.RecipientId,
          this_.RecipientFullName,
          this_.RecipientEmployeeNumber,
          this_.RecipientTitle
) AS Query

每次我尝试让行计数起作用时，NH 都会删除 GROUP BY。上面的 SQL 按我的预期工作。

关于如何让 NHibernate 吐出该 SQL 的任何想法？

Answer 1

NHibernate 中的“标准”方式是创建一个克隆查询：

var rowCountQuery = query.ToRowCountQuery();

哪个（来自文档）：

克隆QueryOver，删除订单和分页，并投影查询的行数

但正如你已经（肯定）在这里体验过的那样......这将导致纯粹的查询（因为所有必需的都被删除了，请参阅下面的查询） - 返回错误结果

SELECT Count(*) FROM   [IssuanceReportLog] -- notwhat needed

解决方案：

将 magical sql sn-p 注入到投影中：

COUNT(*) OVER() AS TotalRowCount

这将准确返回我们需要的内容。总行数over 我们的查询。我们必须扩展 DTO：

public class TopReceiver
{
    ...
    public virtual int TotalRowCount { get; set; }

并像这样调整投影

query.Select(
    ... // all the GROUP BY statements
    // the total row count
    Projections.SqlProjection(" COUNT(*) OVER() AS TotalRowCount "
                   , new string[] { "TotalRowCount" }
                   , new IType[] { NHibernateUtil.Int32 })
    // count, sum
    Projections.Count<IssuanceReportLogEntity>(x=>x.RecipientGroupId)
               .WithAlias(()=>receiver.RecognitionTotalReceived),
    Projections.Sum<IssuanceReportLogEntity>(x=>x.Points)
               .WithAlias(()=>receiver.TotalPoints)
);

稍后我们甚至可以应用分页，但TotalRowCount 的值仍然是正确的。

query
    .Skip(100)
    .Take(25)

现在，每个（包括第一个）结果都包含有关总行数的信息。

var rowCount = list[0].TotalRowCount;

注意：你知道吗？ 这实际上是获取row-count 的最有效方法。不仅在 one server-db 往返中，甚至在 one sql 语句执行中...