实体框架6查询性能（MM关系）

Question

I need to query multiple columns from multiple tables using EF. All goes well and with nice performance when i don't include a MM Relationship in the select query.

Query with MM Relationship:

result = (from s in db.Member
                      .Include(i => i.Category)
                      .Include(i => i.MemberWorkEntity)
                      .Include(i => i.Status)
                      .Include(i => i.DiscountMethod)
                      .Where(i => i.C_deleted == null)
      select new MemberDTO
      {
          memberNumber = s.memberNumber,
          name = s.name,
          status = s.Status.name,
          email = s.email,
          phone = s.phone,
          mobile = s.mobile,
          fax = s.fax,
          workEntity = (from e in db.WorkEntity.Where(i => i.workEntityLevelID == 2)
                        join sc in s.MemberWorkEntity on e.workEntityID equals sc.workEntityID
                        select e.name).FirstOrDefault(),
          category = s.Category.name,
          discountMethod = s.DiscountMethod.name,
          delegate = s.delegate ? "Yes" : "No",
          leader = s.leader ? "Yes" : "No"

      }).AsNoTracking().ToList<MemberDTO>();

30000 records execution time (ms):

|1st Execution: 1376
|2nd Execution: 160
|3rd Execution: 145

Query without MM Relationship:

result = (from s in db.Member
                      .Include(i => i.Category)
                      .Include(i => i.MemberWorkEntity)
                      .Include(i => i.Status)
                      .Include(i => i.DiscountMethod)
                      .Where(i => i.C_deleted == null)
      select new MemberDTO
      {
          memberNumber = s.memberNumber,
          name = s.name,
          status = s.Status.name,
          email = s.email,
          phone = s.phone,
          mobile = s.mobile,
          fax = s.fax,
          //removed M-M Relationship Query
          category = s.Category.name,
          discountMethod = s.DiscountMethod.name,
          delegate = s.delegate ? "Yes" : "No",
          leader = s.leader ? "Yes" : "No"

      }).AsNoTracking().ToList<MemberDTO>();

30000 records execution time (ms):

|1st Execution: 1286
|2nd Execution: 79
|3rd Execution: 67

Why such a difference (2x slower in average)? How can i improve the query performance?

UPDATE: Relationship between Member and WorkEntity

UPDATE: Updated my query based on @AndreFilimon's suggestion:

IEnumerable<WorkEntity> workEntities = db.WorkEntity.AsNoTracking().Where(i => i.workEntityLevelID == 2);

result = (from s in db.Member
                      .Include(i => i.Category)                          
                      .Include(i => i.Status)
                      .Include(i => i.DiscountMethod)
                      .Where(i => i.C_deleted == null)
      select new MemberDTO
      {
          memberNumber = s.memberNumber,
          name = s.name,
          status = s.Status.name,
          email = s.email,
          phone = s.phone,
          mobile = s.mobile,
          fax = s.fax,
          workEntity = (from e in workEntities
                        join sc in s.MemberWorkEntity on e.workEntityID equals sc.workEntityID
                        select e.name).FirstOrDefault(),
          category = s.Category.name,
          discountMethod = s.DiscountMethod.name,
          delegate = s.delegate ? "Yes" : "No",
          leader = s.leader ? "Yes" : "No"

      }).AsNoTracking().ToList<MemberDTO>();

30000 records execution time (ms):

|1st Execution: 1364
|2nd Execution: 122
|3rd Execution: 120

UPDATE: Added a simple index to my Member table as @agfc suggested:

IEnumerable<WorkEntity> workEntities = db.WorkEntity.AsNoTracking().Where(i => i.workEntityLevelID == 2);

result = (from s in db.Member
                      .Include(i => i.Category)                          
                      .Include(i => i.Status)
                      .Include(i => i.DiscountMethod)
                      .Where(i => i.C_deleted == null)
      select new MemberDTO
      {
          memberNumber = s.memberNumber,
          name = s.name,
          status = s.Status.name,
          email = s.email,
          phone = s.phone,
          mobile = s.mobile,
          fax = s.fax,
          workEntity = (from e in workEntities
                        join sc in s.MemberWorkEntity on e.workEntityID equals sc.workEntityID
                        select e.name).FirstOrDefault(),
          category = s.Category.name,
          discountMethod = s.DiscountMethod.name,
          delegate = s.delegate ? "Yes" : "No",
          leader = s.leader ? "Yes" : "No"

      }).AsNoTracking().ToList<MemberDTO>();

30000 records execution time (ms):

|1st Execution: 1544
|2nd Execution: 109
|3rd Execution: 105

UPDATE: Changed query based on @Klinger's answer:

result = db.MemberWorkEntity.Where(mw => mw.WorkEntity.workEntityLevelID == 2 && mw.Member.C_deleted == null)
        .Select(s => new MemberDTO 
        {
            memberNumber = mw.Member.memberNumber,
            name = mw.Member.name,
            status = mw.Member.Status.name,
            email = mw.Member.email,
            phone = mw.Member.phone,
            mobile = mw.Member.mobile,
            fax = mw.Member.fax,
            workEntity = mw.WorkEntity.name,
            category = mw.Member.Category.name,
            discountMethod = mw.Member.DiscountMethod.name,
            @delegate = mw.Member.@delegate ? "Yes" : "No",
            leader = mw.Member.leader ? "Yes" : "No"
        }).ToList();

30000 records execution time (ms):

|1st Execution: 1427
|2nd Execution: 80
|3rd Execution: 76

Answer 1

Without looking at the exact shape of your entities, something like the following should do:

result = db.MemberWorkEntity.Where(mw => mw.WorkEntity.workEntityLevelID == 2 && mw.Member.C_deleted == null)
        .Select(s => new MemberDTO 
{
  memberNumber = mw.Member.memberNumber,
  name = mw.Member.name,
  status = mw.Member.Status.name,
  email = mw.Member.email,
  phone = mw.Member.phone,
  mobile = mw.Member.mobile,
  fax = mw.Member.fax,
  workEntity = mw.WorkEntity.name,
  category = mw.Member.Category.name,
  discountMethod = mw.Member.DiscountMethod.name,
  @delegate = mw.Member.@delegate ? "Yes" : "No",
  leader = mw.Member.leader ? "Yes" : "No"
}).ToList();

No need to use Include because you are projecting into a DTO not an entity. The DTO won't have the navigation properties to the entities you are including. Include is used for eager loading when entities are returned.

Answer 2

Try to move the includes after the where clause, you should get some overall performance here also: Also move the inner query out of the main query to avoid joins as bellow:

var workEntities=(from e in db.WorkEntity).Where(e=>e.workEntityLevelID==2).ToList();
var result = (from s in db.Member.Where(i => i.C_deleted == null).Include(i => i.Category).Include(i => i.MemberWorkEntity).Include(i => i.Status).Include(i => i.DiscountMethod)
          select new MemberDTO
          {
              memberNumber = s.memberNumber,
              name = s.name,
              status = s.Status.name,
              email = s.email,
              phone = s.phone,
              mobile = s.mobile,
              fax = s.fax,
              workEntity = workEntities.Where(e=>e.workEntityID ==sc.workEntityID).DefaultIfEmpty().Select(e=>e.name).FirstOrDefault(),
              category = s.Category.name,
              discountMethod = s.DiscountMethod.name,
              delegate = s.delegate ? "Yes" : "No",
              leader = s.leader ? "Yes" : "No"

          }).AsNoTracking().ToList<MemberDTO>();