NH-3435 - Ability to select the root entity in a criteria projection #302

rjperes · 2014-08-14T10:22:27Z

https://nhibernate.jira.com/browse/NH-3435 (#948)

oskarb · 2014-08-17T11:49:47Z

I'm afraid I don't follow... This appears to be only new code - what is being cleaned up?

hazzik · 2014-08-17T11:58:48Z

There was a broken pull request #299

hazzik · 2014-09-21T12:24:01Z

Hi @rjperes,

I've cleaned up your old pull request with:

D:\Projects\NHibernate\nhibernate-core>git checkout NH-3435
Branch NH-3435 set up to track remote branch NH-3435 from rjperes.
Switched to a new branch 'NH-3435'

D:\Projects\NHibernate\nhibernate-core>git rebase upstream/master -Xrenormalize
First, rewinding head to replay your work on top of it...
Auto-merging src/NHibernate/NHibernate.csproj
Auto-merging src/NHibernate/Criterion/Projections.cs
Auto-merging src/NHibernate.Test/Criteria/ProjectionsTest.cs
[detached HEAD c267a58] Cleaning up pull request
Author: Ricardo Peres [email protected]
6 files changed, 264 insertions(+)
create mode 100644 src/NHibernate/Criterion/BaseEntityProjection.cs
create mode 100644 src/NHibernate/Criterion/EntityProjection.cs
create mode 100644 src/NHibernate/Criterion/RootEntityProjection.cs
Committed: 0001 Cleaning up pull request
All done.

D:\Projects\NHibernate\nhibernate-core>git push rjperes NH-3435:NH-3435 -f
Counting objects: 22, done.
Delta compression using up to 8 threads.
Compressing objects: 100% (12/12), done.
Writing objects: 100% (13/13), 2.84 KiB | 0 bytes/s, done.
Total 13 (delta 10), reused 3 (delta 1)
To [email protected]:rjperes/nhibernate-core.git

d4f9a4e...c267a58 NH-3435 -> NH-3435 (forced update)

hazzik · 2014-10-09T23:18:33Z

Restarting tests

rjperes · 2014-10-10T08:13:24Z

BTW: can you lower the priority from Major to something else? And will it be in 4.1?

X

danspam · 2016-03-01T05:59:46Z

Looks to me like this new code only selects the identifier of the root entity and not all the properties.

rjperes · 2016-03-01T07:34:34Z

Did you try it?

danspam · 2016-03-01T07:44:00Z

Yes I did, and the SQL produced only selects the identifier. The way I read it, the code that retrieves the column names and alias name in IProjection.ToSqlString() just retrieves the identifier column name and alias. The pull request #299 mentioned earlier appears to have code that iterates and retrieves all properties of the entity but this pr does not have this.

Unfortunately my knowledge of this code base is non-existent and I would not dare hazard a guess at the fix for this.

rjperes · 2016-03-01T08:36:43Z

This works as expected, AFAIK.
Did you see the unit tests? Are they failing?

danspam · 2016-03-02T03:00:20Z

The unit tests are not failing. However, I thought that the purpose of this change was to be able to create a projection of all the properties of the specified entity . This is useful if you have multiple joins in the query and only want to retrieve e.g. the root entity without creating a sql select statement with every property of all the joined entities.

When I run the unit test UseRootProjection(), the generated SQL statement of the select query using Projections.RootEntity() is as follows:

`SELECT
    this_."studentId" as studentId2_ 
FROM
    Student this_ 
WHERE
    this_.studentId = @p0;
@p0 = 667 [Type: Int64 (0)]`

This means that if the entity is not in cache, accessing any of the entities properties will cause an additional query to retrieve the rest of the properties.

bahusoid · 2017-11-23T15:36:38Z

I also really miss the ability to eager fetch entities via QueryOver/Criteria API.
And as @danspam pointed out - this promising pr doesn't allow it either :(.

Regarding unit tests - they check object loading that's already present in session. So tests don't really check that all properties are fetched.

I updated tests to show the issue:

Updated tests

[Test]
public void UseRootProjection()
{
	//NH-3435
	using (ISession session = Sfi.OpenSession())
	using (ITransaction tx = session.BeginTransaction())
	{
		Course course = new Course();
		course.CourseCode = "HIB";
		course.Description = "Hibernate Training";
		session.Save(course);

		Student gavin = new Student();
		gavin.Name = "Gavin King";
		gavin.StudentNumber = 667;
		session.Save(gavin);

		Enrolment enrolment = new Enrolment();
		enrolment.Course = course;
		enrolment.CourseCode = course.CourseCode;
		enrolment.Semester = 1;
		enrolment.Year = 1999;
		enrolment.Student = gavin;
		enrolment.StudentNumber = gavin.StudentNumber;
		gavin.Enrolments.Add(enrolment);
		session.Save(enrolment);
		session.Flush();
				
		//Clear session to make sure entity is eager fetched
		session.Clear();

		Student g = session.CreateCriteria(typeof(Student))
			.Add(Expression.IdEq(gavin.StudentNumber))
			.SetFetchMode("Enrolments", FetchMode.Join)
			.SetProjection(Projections.RootEntity())
			.UniqueResult<Student>();

		Assert.That(NHibernateUtil.IsInitialized(g), Is.True, "object must be initialized");
		Assert.That(g, Is.EqualTo(gavin).Using((Student x, Student y) => x.StudentNumber == y.StudentNumber && x.Name == y.Name ? 0 : 1));
	}
}

[Test]
public void UseEntityProjection()
{
	//NH-3435
	using (ISession session = Sfi.OpenSession())
	using (ITransaction tx = session.BeginTransaction())
	{
		Course course = new Course();
		course.CourseCode = "HIB";
		course.Description = "Hibernate Training";
		session.Save(course);

		Student gavin = new Student();
		gavin.Name = "Gavin King";
		gavin.StudentNumber = 667;
		session.Save(gavin);

		Enrolment enrolment = new Enrolment();
		enrolment.Course = course;
		enrolment.CourseCode = course.CourseCode;
		enrolment.Semester = 1;
		enrolment.Year = 1999;
		enrolment.Student = gavin;
		enrolment.StudentNumber = gavin.StudentNumber;
		gavin.Enrolments.Add(enrolment);
		session.Save(enrolment);
		session.Flush();

		//Clear session to make sure entity is eager fetched
		session.Clear();

		Student g = session.CreateCriteria(typeof(Enrolment))
			.Add(Expression.And(Expression.Eq("StudentNumber", gavin.StudentNumber), Expression.Eq("CourseCode", course.CourseCode)))
			.CreateAlias("Student", "s", JoinType.InnerJoin)
			.SetProjection(Projections.Entity<Student>("s"))
			.UniqueResult<Student>();

		Assert.That(NHibernateUtil.IsInitialized(g), Is.True, "object must be initialized");
		Assert.That(g, Is.EqualTo(gavin).Using((Student x, Student y) => x.StudentNumber == y.StudentNumber && x.Name == y.Name ? 0 : 1));
	}
}

bahusoid · 2017-11-23T18:11:30Z

Updated tests can also be found here (rebased with master): https://github.com/bahusoid/nhibernate-core/commits/GH948.

bahusoid · 2017-11-23T19:03:09Z

Yayk! It's actually possible to eager fetch. It's just not exposed for some reasons via Projections helper methods. But it's possible via:
.SetProjection(new RootEntityProjection().SetLazy(false))
.SetProjection(new EntityProjection<Student>("s").SetLazy(false))

I think SetLazy should be definitely exposed via additional parameter (or maybe Projections helper methods should simply return exact class instead of IProjection interface)

fredericDelaporte · 2017-11-23T19:12:10Z

If you wish to tackle this subject, PR your rebase and go ahead with required changes, it will then replace this PR.

Update: I am not sure this PR was actually about eager fetching. If you change things about it, it may be better to do it as a separated PR.

bahusoid · 2017-11-24T05:01:08Z

@fredericDelaporte No changes needed (except small changes to better expose already present functionality). This PR allows to retrieve entity as projection both ways (as lazy and eager fetched). Ok I will add separate tests for lazy and eager part and submit a new PR for this.

hazzik · 2017-11-28T21:25:29Z

Replaced by #1458

oskarb changed the title ~~Cleaning up pull request~~ NH-3435 Ability to select the root entity in a criteria projection Sep 2, 2014

rjperes mentioned this pull request Sep 21, 2014

NH-3435 #299

Closed

hazzik force-pushed the master branch from eb44257 to 4b88cc1 Compare September 21, 2014 13:52

hazzik added this to the 4.1.0 milestone Nov 18, 2014

hazzik changed the title ~~NH-3435 Ability to select the root entity in a criteria projection~~ NH-3435 - Ability to select the root entity in a criteria projection Apr 22, 2015

NH-3435 - Ability to select the root entity in a criteria projection

1da08d4

X

hazzik closed this Apr 22, 2015

hazzik reopened this Apr 22, 2015

hazzik modified the milestones: 4.2.0, 4.1.0 Aug 12, 2016

hazzik force-pushed the master branch from e20411b to 9b7a5a3 Compare October 26, 2016 01:26

hazzik modified the milestones: 4.2.0, 5.0.0 Dec 1, 2016

hazzik modified the milestones: 5.0, 5.1 Aug 25, 2017

nhibernate-bot mentioned this pull request Oct 12, 2017

NH-3435 - Ability to select entities in Criteria projections #948

Closed

bahusoid mentioned this pull request Nov 28, 2017

#948(NH-3435) - Ability to select entities in a criteria projections (rebased PR #302) #1458

Closed

hazzik closed this Nov 28, 2017

hazzik added r: Replaced t: Fix p: Minor t: New Feature labels Nov 28, 2017

hazzik removed this from the 5.1 milestone Nov 28, 2017

bahusoid mentioned this pull request Dec 3, 2017

Ability to select entities in Criteria projections #1471

Merged

NH-3435 - Ability to select the root entity in a criteria projection #302

NH-3435 - Ability to select the root entity in a criteria projection #302

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