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我是 graphql 的新手，目前正在参加 ChilliCream graphql 研讨会。在遵循此之后实施分页后

有一个注释：“在我们的 TrackType 实现中有一个警告。因为，我们在解析器中使用 DataLoader 并首先获取 ID 列表，我们基本上总是会获取所有内容并切入内存。在实际项目中通过将 DataLoader 部分移动到中间件和可查询 id 上的第一页，这可以分为两个动作。也可以实现一个特殊的 IPagingHandler，它使用 DataLoader 并应用分页逻辑。

我一直无法弄清楚如何拆分这两个动作。任何帮助，将不胜感激。

询问

query GetTrackWithSessions {
  trackById(id: "VHJhY2sKaTE=") {
    id
    sessions(first: 1) {      
      nodes {
        title
      }      
    }
  }
}

跟踪查询

public Task<Track> GetTrackByIdAsync(
            [ID(nameof(Track))] int id,
            TrackByIdDataLoader trackById,
            CancellationToken cancellationToken) =>
            trackById.LoadAsync(id, cancellationToken);

轨道类型

public class TrackType : ObjectType<Track>
    {
        protected override void Configure(IObjectTypeDescriptor<Track> descriptor)
        {
            descriptor
                .ImplementsNode()
                .IdField(t => t.Id)
                .ResolveNode((ctx, id) =>
                    ctx.DataLoader<TrackByIdDataLoader>().LoadAsync(id, ctx.RequestAborted));

            descriptor
                .Field(t => t.Sessions)
                .ResolveWith<TrackResolvers>(t => t.GetSessionsAsync(default!, default!, default!, default))
                .UseDbContext<ApplicationDbContext>()
                .UsePaging<NonNullType<SessionType>>()
                .Name("sessions");

            descriptor
                .Field(t => t.Name)
                .UseUpperCase();
        }

        private class TrackResolvers
        {
            public async Task<IEnumerable<Session>> GetSessionsAsync(
                Track track,
                [ScopedService] ApplicationDbContext dbContext,
                SessionByIdDataLoader sessionById,
                CancellationToken cancellationToken)
            {
                int[] sessionIds = await dbContext.Sessions
                    .Where(s => s.Id == track.Id)
                    .Select(s => s.Id)
                    .ToArrayAsync();

                return await sessionById.LoadAsync(sessionIds, cancellationToken);
            }
        }
    }

数据加载器

public class TrackByIdDataLoader : BatchDataLoader<int, Track>
    {
        private readonly IDbContextFactory<ApplicationDbContext> _dbContextFactory;

        public TrackByIdDataLoader(
            IBatchScheduler batchScheduler, 
            IDbContextFactory<ApplicationDbContext> dbContextFactory)
            : base(batchScheduler)
        {
            _dbContextFactory = dbContextFactory ?? 
                throw new ArgumentNullException(nameof(dbContextFactory));
        }

        protected override async Task<IReadOnlyDictionary<int, Track>> LoadBatchAsync(
            IReadOnlyList<int> keys, 
            CancellationToken cancellationToken)
        {
            await using ApplicationDbContext dbContext = 
                _dbContextFactory.CreateDbContext();

            *All the tracks are returned here
            return await dbContext.Tracks
                .Where(s => keys.Contains(s.Id))
                .ToDictionaryAsync(t => t.Id, cancellationToken);
        }
    }

谢谢

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