Filter data before lookup(join) two collections in mongodb

[855]

I'm writing a function which will join two collections and two filters for each.

public class Teacher
{
public string Id{ get; set; }
public string Name{ get; set; }
public string TeacherFilter{ get; set; }
...
}

public class Student
{
public string Id{ get; set; }
public string Name{ get; set; }
public string StudentFilter{ get; set; }
public string TeacherId{ get; set; }
...
}

public class TeacherStudents
{
public string Id{ get; set; } -- from teacher
public string Name{ get; set; } -- from teacher
public IEnumerable<Student> Students{get;set;}
}

public class TeacherStudents
{
public string Id{ get; set; } -- from teacher
public string Name{ get; set; } -- from teacher
public IEnumerable<Student> Student{get;set;}
}

public class TeacherStudent
{
public string Id{ get; set; } -- from teacher
public string Name{ get; set; } -- from teacher
...
public Student Student{get;set;}
}

Get(string TeacherFilter,string StudentFilter).

Here is how i implement it

var query = teacherCollection.Aggregate().Match(x => x.TeacherFilter== TeacherFilter); //filter teach
var query1 = query
.Lookup<Teacher, Student, TeacherStudent>(studentCollection, t => t.Id, s => s.TeacherId, l => l.Student)
.Unwind(x => x.Student, new AggregateUnwindOptions<TeacherStudent>())
.Match(x => x.StudentFilter== StudentFilter) //filter student

For the teacher collection, useless data has been filter out which will reduce the data size when doing the lookup(join). But for the student collection, the match stage is appended after the lookup. so does all the data from student will join with teacher behind the scenes? is it possible to filter out some student data before the lookup?

[Richard Deeming]

You have already posted this in QA: Filter data before lookup(join) two collections in mongodb[^]

---

"These people looked deep within my soul and assigned me a number based on the order in which I joined." - Homer

[855]

why no one answer it?

[Richard Deeming]

You posted it less than 12 hours ago. Half the world won't have woken up and had a chance to to read it yet. And since questions here are answered by volunteers, nobody is under any obligation to answer it at all, let alone within a defined time limit.

---

"These people looked deep within my soul and assigned me a number based on the order in which I joined." - Homer