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ProduceCTEThatCanReturnTheUpwardRecommendationChainForAnyMember.cs
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ProduceCTEThatCanReturnTheUpwardRecommendationChainForAnyMember.cs
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using System.Linq;
using EFCorePgExercises.DataLayer;
using System.Collections.Generic;
using FluentAssertions;
using EFCorePgExercises.Utils;
using LinqToDB.EntityFrameworkCore;
using LinqToDB;
namespace EFCorePgExercises.Exercises.RecursiveQueries
{
[FullyQualifiedTestClass]
public class ProduceCTEThatCanReturnTheUpwardRecommendationChainForAnyMember
{
[FullyQualifiedTestMethod]
public void Test_Method1()
{
// https://pgexercises.com/questions/recursive/getupwardall.html
// Produce a CTE that can return the upward recommendation chain for any member.
// You should be able to select recommender from recommenders where member=x.
// Demonstrate it by getting the chains for members 12 and 22. Results table should have
// member and recommender, ordered by member ascending, recommender descending.
//
//with recursive recommenders(recommender, member) as (
// select recommendedby, memid
// from cd.members
// union all
// select mems.recommendedby, recs.member
// from recommenders recs
// inner join cd.members mems
// on mems.memid = recs.recommender
//)
//select recs.member member, recs.recommender, mems.firstname, mems.surname
// from recommenders recs
// inner join cd.members mems
// on recs.recommender = mems.memid
// where recs.member = 22 or recs.member = 12
//order by recs.member asc, recs.recommender desc
EFServiceProvider.RunInContext(context =>
{
var id1 = 12;
var id2 = 22;
var entityWithAllOfItsParents =
context.Members
.Where(member => member.MemId == id1 || member.MemId == id2
|| member.Children.Any(m => member.MemId == m.RecommendedBy))
.ToList(); //It's a MUST - get all children from the database
/*
SELECT [m].[MemId], [m].[Address], [m].[FirstName], [m].[JoinDate], [m].[RecommendedBy], [m].[Surname], [m].[Telephone], [m].[ZipCode]
FROM [Members] AS [m]
WHERE (([m].[MemId] = @__id1_0) OR ([m].[MemId] = @__id2_1)) OR EXISTS (
SELECT 1
FROM [Members] AS [m0]
WHERE ([m].[MemId] = [m0].[RecommendedBy]) AND ([m].[MemId] = [m0].[RecommendedBy]))
*/
var expectedResultFor12 = new[]
{
new { Recommender = 9, FirstName = "Ponder", Surname ="Stibbons" },
new { Recommender = 6, FirstName = "Burton", Surname ="Tracy" }
};
var actualResultFor12 = new List<dynamic>();
RecursiveUtils.FindParents(entityWithAllOfItsParents.FirstOrDefault(x => x.MemId == id1), actualResultFor12);
actualResultFor12.Should().BeEquivalentTo(expectedResultFor12);
var expectedResultFor22 = new[]
{
new { Recommender = 16, FirstName = "Timothy", Surname ="Baker" },
new { Recommender = 13, FirstName = "Jemima", Surname ="Farrell" }
};
var actualResultFor22 = new List<dynamic>();
RecursiveUtils.FindParents(entityWithAllOfItsParents.FirstOrDefault(x => x.MemId == id2), actualResultFor22);
actualResultFor22.Should().BeEquivalentTo(expectedResultFor22);
});
}
[FullyQualifiedTestMethod]
public void Test_Method2()
{
// https://pgexercises.com/questions/recursive/getupwardall.html
// Produce a CTE that can return the upward recommendation chain for any member.
// You should be able to select recommender from recommenders where member=x.
// Demonstrate it by getting the chains for members 12 and 22. Results table should have
// member and recommender, ordered by member ascending, recommender descending.
// Using
// https://github.com/linq2db/linq2db.EntityFrameworkCore
// https://linq2db.github.io/articles/sql/CTE.html
EFServiceProvider.RunInContext(context =>
{
var memberHierarchyCte =
context.CreateLinqToDBContext().GetCte<MemberHierarchyCTE>(memberHierarchy =>
{
return
(
from member in context.Members
select new MemberHierarchyCTE
{
ChildId = member.MemId,
ParentId = member.RecommendedBy
}
)
.Concat
(
from member in context.Members
from hierarchy in memberHierarchy
.InnerJoin(hierarchy => member.MemId == hierarchy.ParentId)
select new MemberHierarchyCTE
{
ChildId = hierarchy.ChildId,
ParentId = member.RecommendedBy
}
);
});
var parentIdsQuery = memberHierarchyCte.Where(mh => (mh.ChildId == 12 || mh.ChildId == 22) && mh.ParentId != null)
.Select(mh => mh.ParentId);
var parents = context.Members.Where(member => parentIdsQuery.Contains(member.MemId))
.Select(member => new
{
Recommender = member.MemId,
member.FirstName,
member.Surname
})
.OrderByDescending(result => result.Recommender)
.ToLinqToDB()
.ToList();
/*
WITH [memberHierarchy] ([ChildId], [ParentId])
AS
(
SELECT
[member_1].[MemId],
[member_1].[RecommendedBy]
FROM
[Members] [member_1]
UNION ALL
SELECT
[hierarchy_1].[ChildId],
[member_2].[RecommendedBy]
FROM
[Members] [member_2]
INNER JOIN [memberHierarchy] [hierarchy_1] ON [member_2].[MemId] = [hierarchy_1].[ParentId]
)
SELECT
[member_3].[MemId],
[member_3].[FirstName],
[member_3].[Surname]
FROM
[Members] [member_3]
WHERE
EXISTS(
SELECT
*
FROM
[memberHierarchy] [mh]
WHERE
([mh].[ChildId] = 12 OR [mh].[ChildId] = 22) AND [mh].[ParentId] IS NOT NULL AND
[mh].[ParentId] = [member_3].[MemId]
)
ORDER BY
[member_3].[MemId] DESC
*/
var expectedResult = new[]
{
new { Recommender = 16, FirstName = "Timothy", Surname ="Baker" },
new { Recommender = 13, FirstName = "Jemima", Surname ="Farrell" },
new { Recommender = 9, FirstName = "Ponder", Surname ="Stibbons" },
new { Recommender = 6, FirstName = "Burton", Surname ="Tracy" }
};
parents.Should().BeEquivalentTo(expectedResult);
});
}
}
}