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Limit

The limit parameter restricts the maximum number of items returned in a single response. It is commonly used for pagination in combination with the skip parameter.

Syntax

  • limit(value: Integer)

Examples:

  • limit(10)
  • limit(100)

C# representation

The limit parameter is represented by the Limit node in C#. For example:

limit(10)

corresponds to:

new Limit(new Constant(10));

The Limit node has a single child, a Constant node containing the maximum number of items to return.

Configuration

Enable the limit parameter for a request by calling the SupportsLimit() method. Optionally, pass an action to configure the parameter further, for example, to set the default and maximum values:

public sealed class ApiSchema : Schema
{ 
    protected override void OnInitializeSchema(ISchemaConfigBuilder schema) 
    {        
        schema.Request("listSets")
            .SupportsLimit(config => 
            {                
                // Return at most 20 items by default
                config.HasDefaultValue(new Limit(new Constant(20)))
                    // Reject values greater than 100
                    .HasMaxLimit(100);
            });
    }
}

Note

If limit is not provided when executing a request and no default is set, the effective behavior is to return all remaining items (depending on the data source used, like EF Core).

Execution

When executing a query with the limit parameter, the Limit node is first validated against the following rules:

  • Value must be an integer.
  • Value must be greater than or equal to 0.
  • Value must be less than or equal to the maximum limit value.

If valid, the Limit node can be applied to the result set:

public sealed record Set(string Name, double Price, DateTime LaunchTime);

var sets = new List<Set>
{
    new("LEGO Star Wars Millennium Falcon", 849.99, new DateTime(2017, 10, 01)),
    new("LEGO Star Wars The Razor Crest", 599.99, new DateTime(2022, 10, 03)),
    new("LEGO DC Batman Batmobile Tumbler", 269.99, new DateTime(2021, 11, 01)),
    new("LEGO Harry Potter Hogwarts Castle", 469.99, new DateTime(2018, 09, 01)),
};

// 'limit(1)' node (e.g., from parsing)
var limit = new Limit(new Constant(1));

// Apply limit to data set
var results = sets.AsQueryable()
    // Equivalent LINQ:
    // .Take(1)
    .ApplyLimit(limit)
    .ToList();

// Print the result
Console.WriteLine(string.Join("\n", results));
// Output:
// Set { Name = LEGO Star Wars Millennium Falcon, Price = 849.99, LaunchTime = 1-10-2017 00:00:00 }

Pagination

Combine the skip and limit parameters to implement page/offset navigation. For example, to get the second page of results with 10 items per page, you can use the following query:

GET http://localhost:5000/sets
  ?skip=10
  &limit=10

listSets(
  skip(10),
  limit(10)
)

Tip

Use a stable sort with paging to avoid item drift between pages (e.g., sort by createTime).