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Skip

The skip parameter specifies how many items to skip from the result set before returning data. It is commonly used for pagination in combination with the limit parameter.

Syntax

  • skip(value: Integer)

Examples:

  • skip(10)
  • skip(20)

C# representation

The skip parameter is represented by the Skip node in C#. For example:

skip(20)

corresponds to:

new Skip(new Constant(20));

The Skip node has a single child, a Constant node containing the number of items to skip.

Configuration

Enable the skip parameter for a request by calling the SupportsSkip() method. Optionally, pass an action to configure the parameter further, for example, to set the default value:

public sealed class ApiSchema : Schema
{ 
    protected override void OnInitializeSchema(ISchemaConfigBuilder schema) 
    {        
        schema.Request("listSets")
            .SupportsSkip(config => 
            {
                // Skip first 20 items by default
                config.HasDefaultValue(new Skip(new Constant(20)));
            });
    }
}

Note

If skip is not provided when executing a request and no default is set, the effective value is 0.

Execution

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

  • Value must be an integer.
  • Value must be greater than or equal to 0.

If valid, the Skip 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)),
};

// 'skip(3)' node (e.g., from parsing)
var skip = new Skip(new Constant(3));

// Apply skip to data set
var results = sets.AsQueryable()
    // Equivalent LINQ:
    // .Skip(3)
    .ApplySkip(skip)
    .ToList();

// Print the result
Console.WriteLine(string.Join("\n", results));
// Output:
// Set { Name = LEGO Harry Potter Hogwarts Castle, Price = 469.99, LaunchTime = 1-9-2018 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).