[英]What is the best way to test a condition in Linq to NHibernate?
Any()linq函數似乎加載了實體的所有列,即使它們並不需要。
如下代碼:
if(Session.Query<Project>().Any(p=>p.ID == projectID && p.ProjectOwner.Responsible == CurrentUserID))
// Current user is the responsible for this project
生成以下SQL:
select TOP (1) project0_.ProjectID as ProjectID7_,
project0_.DateCreated as DateCrea2_7_,
project0_.Type as Type7_,
project0_.ProjectOwner_FK as ProjectOy8_7_,
project0_.Address_FK as Address9_7_,
**[Snip -- the statement selects all of Project's columns]**
from [Project] project0_
inner join [OrganizationProject] organizati1_
on project0_.ProjectOwner_FK = organizati1_.OrganizationProjectID
where project0_.ProjectID = 1 /* @p0 */
and organizati1_.Responsible_FK = 1 /* @p1 */
但是,以下代碼:
if(Context.Projects.Where(p=>p.ID == projectID && p.ProjectOwner.Responsible == CurrentUserID).Count() == 1)
// Current user is the responsible for this project
生成以下sql,這是預期的結果:
select cast(count(*) as INT) as col_0_0_
from [Project] project0_
inner join [OrganizationProject] organizati1_
on project0_.ProjectOwner_FK = organizati1_.OrganizationProjectID
where project0_.ProjectID = 1 /* @p0 */
and organizati1_.Responsible_FK = 1 /* @p1 */
Count()方法可以完成預期的工作,但不太直接。
是Any()行為被認為是正常的還是錯誤? 這對我來說似乎不是最佳選擇,但是也許加載實體並不比要求SQL返回計數慢嗎?
有鑒於此, 什么是在Linq to NHibernate中測試條件的最佳方法?
這很有趣,但是您是否嘗試過:
if(Session.Query<Project>()
.FirstOrDefault(p=>p.ID == projectID
&& p.ProjectOwner.Responsible == CurrentUserID) != null)
我認為從您當前的選擇中可以更快。 實際上,它不會檢查所有項(例如count),也不會獲取所有數據。
這樣的事情應該創建一個僅包含一列的查詢:
if(Session
.Query<Project>()
.Where(p=>p.ID == projectID && p.ProjectOwner.Responsible == CurrentUserID)
.Select(p=>new { pID = p.ID })
.Any())
{
...
}
投影到匿名類型允許NHibernate僅獲取指定的列(例如ID)。
但是,當要檢索的行數量很多時,它通常更適合。
聲明:本站的技術帖子網頁,遵循CC BY-SA 4.0協議,如果您需要轉載,請注明本站網址或者原文地址。任何問題請咨詢:yoyou2525@163.com.