Paging Control

[mjartz]

Description

In v3.1.0 I was able to set a global default page size to 20 in statup.cs which was desirable for most of my resources, however there were a few resources that I didn't want that default to apply to as I wanted every record returned by default, but still wanted paging if a page size was supplied by the client. I was able to achieve this in the controller for the given resource by checking whether a page size was supplied in the context QuerySet, and if not, I would set the context PageManager.PageSize = 0.

public class MyEntityController : BaseJsonApiController<MyEntity>
{
     public MyEntityController(
           IJsonApiContext jsonApiContext,
           IResourceService<MyEntity> resourceService,
           ILoggerFactory loggerFactory)
           : base(jsonApiContext, resourceService, loggerFactory)
       {
           if (jsonApiContext.QuerySet == null || jsonApiContext.QuerySet.PageQuery.PageSize == 0)
               jsonApiContext.PageManager.PageSize = 0;
       }
}

This worked well, but I am unable to achieve this in v4.0.0 using the PageService. I read in a previous issue (#217) of a potential solution to introduce a pagination attribute that could be used on resource definitions and I think this would be great as long as it allowed me to override the global default page size to something different, including equal to zero for no paging by default.

The above is probably a bigger change, so another option might be to:
Modify the PageService class as follows:

• Expose a DefaultPageSize property, defaulted to the global DefaultPageSize value
• Change the PageSize property to a int? and do not initialize it in the constructor
• Set the PageSize property to the value parsed from query parameters, only if supplied
• Add a CalcPageSize property { get => PageSize ?? DefaultPageSize; }

Modify the DefaultResourceService class, ApplyPageQueryAsync method as follows:

protected virtual async Task<IEnumerable<TResource>> ApplyPageQueryAsync(IQueryable<TResource> entities)
{
    if (_pageService.CalcPageSize == 0)
    {
        var allEntities = await _repository.ToListAsync(entities);
        return allEntities as IEnumerable<TResource>;
    }

    int pageOffset = _pageService.CurrentPage;
    if (_pageService.Backwards)
    {
        pageOffset = -pageOffset;
    }
    if (_logger?.IsEnabled(LogLevel.Information) == true)
    {
        _logger?.LogInformation($"Applying paging query. Fetching page {pageOffset} " +
            $"with {_pageService.CalcPageSize} entities");
    }

    return await _repository.PageAsync(entities, _pageService.CalcPageSize, pageOffset);
}

This respects the global default page size and any page sizes supplied in query parameters, but also allows me to modify the page service in a custom resource service to set PageSize = 0 to default to no paging.

public class MyEntityService : DefaultResourceService<MyEntity>
{
    public MyEntityService(
        IEnumerable<IQueryParameterService> queryParameters,
        IJsonApiOptions options,
        IResourceRepository<MyEntity> repository,
        IResourceContextProvider provider,
        ILoggerFactory loggerFactory = null)
        : base(queryParameters, options, repository, provider, null, loggerFactory)
    {
        var pageService = queryParameters.FirstOrDefault<IPageService>();
        pageService.PageSize = 0;
    }
}

I could also set a different DefaultPageSize for a given entity service as well if i wanted it different to the global option.

Thanks guys and keep up the great work.

Environment

• JsonApiDotNetCore Version: 4.0.0.0 alpha 4
• Other Relevant Package Versions:

[maurei]

Hi @mjartz, thanks for the clear feedback. Indeed, DefaultPageSize was exposed before and I wasn't sure why that was, but this appears to be a valid use-case for that.

The proposed attribute in #217 is nice, but currently not very high up my todo-list. I processed your request in #642 :)

Cheers