ef core 6/mysql performance issue

Question

I am having a strange performance issue with ef core 6 and MySlq and hoping you can help me spot the problem. here's my setup.

1. Ef core 6/ Mysql

2. Table per Hierarchy approach. Here's the hierarchy:

    public class RealEstate : Property{ }

3. Repository pattern with UnitOfWork. Here it is:

    public interface IUnitOfWork { IDataAccessLayer<Property> PropertyRepository { get; } IDataAccessLayer<RealEstate> RealEstateRepository { get; } }

4. Here's my database context:

    public class MeerkatContext : IdentityDbContext<AppUser> { public MeerkatContext(DbContextOptions<MeerkatContext> options) : base(options) { } public DbSet<Property> Property { get; set; } public DbSet<RealEstate> RealEstate { get; set; } }

5. I have the following index defined on the "property" table

6. I have 1 million records in the table.

Here's the issue:

The following query take less than 1 seconds:

var count1 = await this._unitOfWork.PropertyRepository.CountAsync(x =>
    x.CountryId == 1 && !x.IsBlocked && x.IsPublic);
    

this one takes 10 seconds:

var count2 = await this._unitOfWork.RealEstateRepository.CountAsync(x =>
     x.CountryId == 1 && !x.IsBlocked && x.IsPublic);

I am stomped. Any help would be really appreciated.

edited to show query excution in MySql WorkBench

Thanks

Answer 1

Sind you probably want to search for un-blocked items, change the logic to help with the SQL:

AND NOT IsBlocked -- inefficient
AND IsBlocked = 0 -- efficient (using "=" instead of "NOT")
AND NotBlocked -- efficient (flip the name and logic)

In general: avoid OR and NOT when constructing SQL. (This is an oversimplification.)

Then add this 4-column index to the table:

INDEX(CountryId, IsBlocked [or NotBlocked], IsPublic, CategoryName)

Look through the rest of the schema for similar changes.