Question 198740 in ASP.NET Question posted in
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Asp.net – Include() not working with Take() when performing a split query

I have collection of Images in my Product class:

public ICollection<Image> Images { get; set; } = null!;

I ran into problem where Images are not being included when I try to take only 4 first products.
This code includes images

var products = await _context.Products
            .Include(x => x.Images)
            .AsSplitQuery()
            .ToListAsync();

But this does not include them

var products = await _context.Products
            .Take(4)
            .Include(x => x.Images)
            .AsSplitQuery()
            .ToListAsync();

This is SQL generated with Take

This is without Take

Also when I am including other entities, Images are also being included.
For example, I have Brand field in Product class

public int BrandId { get; set; }
public Brand Brand { get; set; } = null!;

And this code includes both Brand and Images

var products = await _context.Products
            .Take(4)
            .Include(x => x.Images)
            .Include(x => x.Brand)
            .AsSplitQuery()
            .ToListAsync();

Why it does not include Images when I use Take method?
I can change to a single query or use Select() to specify what i need to get and it will work.
But I want to know what is the problem with split query.
I use PostgreSQL as my database.

Tags:

2

Answers


  1. 0

    EF Core is generating a SQL query that includes a LIMIT clause to fetch only the specified number of products. However, when EF Core splits the query and executes separate queries for related entities, it doesn’t include the LIMIT clause in those queries. This use can clearly see in the generated queries.

    You could use the split query if this fulfils your requirement.

    var products = await _context.Products
    .Take(4)
    .Include(x => x.Images)
    .ToListAsync();

    Or you can run separate queries.

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  2. 0

    When you use Take() before Include(), EF Core generates a SQL query that includes a LIMIT clause to fetch only the specified number of products. However, when EF Core splits the query and executes separate queries for related entities, it doesn’t include the LIMIT clause in those queries.

    You can try removing AsSplitQuery() =>

    var products = await _context.Products
    .Take(4)
    .Include(x => x.Images)
    .ToListAsync();

    Or

    Split the queries =>

    var products = await _context.Products
    .Take(4)
    .ToListAsync();

foreach (var product in products)
{
    await _context.Entry(product)
        .Collection(x => x.Images)
        .LoadAsync();
}
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