游标分页优化

src/Jiaowu.Api/Controllers/DegreeAwardsController.cs

@@ -1,4 +1,5 @@
 using System.ComponentModel.DataAnnotations;
+using Jiaowu.Api.Contracts;
 using Jiaowu.Api.Domain.Academic;
 using Jiaowu.Api.Domain.Identity;
 using Jiaowu.Api.Infrastructure.Auth;
@@ -62,14 +63,15 @@ public sealed class DegreeAwardsController(
     [Authorize(Roles = Reviewers)]
     public async Task<ActionResult> GetBatch(
         Guid id,
-        [FromQuery] int page = 1,
+        [FromQuery] string? cursor = null,
         [FromQuery] int pageSize = 20,
         [FromQuery] string? keyword = null,
         [FromQuery] DegreeAwardConclusion? conclusion = null,
         CancellationToken token = default)
     {
-        page = Math.Max(page, 1);
         pageSize = Math.Clamp(pageSize, 10, 100);
+        if (!CursorToken.TryDecode<DegreeResultCursor>(cursor, out var after))
+            return BadRequest("学位授予结果游标无效。");
         var batch = await db.DegreeAwardBatches.AsNoTracking()
             .FirstOrDefaultAsync(x => x.Id == id, token);
         if (batch is null) return NotFound();
@@ -104,9 +106,13 @@ public sealed class DegreeAwardsController(
             source = source.Where(x => x.Conclusion == conclusion.Value);
 
         var total = await source.CountAsync(token);
-        var items = await source.OrderBy(x => x.Student!.StudentNumber)
-            .Skip((page - 1) * pageSize)
-            .Take(pageSize)
+        if (after is not null)
+        {
+            source = source.Where(x => x.Student!.StudentNumber.CompareTo(after.StudentNumber) > 0 ||
+                x.Student.StudentNumber == after.StudentNumber && x.Id.CompareTo(after.Id) > 0);
+        }
+        var rows = await source.OrderBy(x => x.Student!.StudentNumber).ThenBy(x => x.Id)
+            .Take(pageSize + 1)
             .Select(x => new
             {
                 x.Id,
@@ -124,6 +130,9 @@ public sealed class DegreeAwardsController(
                 x.ReviewComment,
                 x.ReviewedAt
             }).ToListAsync(token);
+        var hasMore = rows.Count > pageSize;
+        var items = rows.Take(pageSize).ToArray();
+        var last = items.LastOrDefault();
 
         return Ok(new
         {
@@ -144,12 +153,16 @@ public sealed class DegreeAwardsController(
             {
                 Items = items,
                 Total = total,
-                Page = page,
+                HasMore = hasMore,
+                NextCursor = hasMore && last is not null
+                    ? CursorToken.Encode(new DegreeResultCursor(last.StudentNumber, last.Id)) : null,
                 PageSize = pageSize
             }
         });
     }
 
+    private sealed record DegreeResultCursor(string StudentNumber, Guid Id);
+
     [HttpPost("batches")]
     [Authorize(Roles = Managers)]
     public async Task<ActionResult> Create(