游标分页优化

src/Jiaowu.Api/Controllers/CourseAdjustmentsController.cs

@@ -177,12 +177,14 @@ public sealed class CourseAdjustmentsController(
     public async Task<ActionResult> GetMine(
         Guid? academicTermId,
         CourseAdjustmentStatus? status,
-        int page = 1,
+        string? cursor = null,
         int pageSize = 20,
         CancellationToken cancellationToken = default)
     {
-        if (page < 1 || pageSize is < 1 or > 100)
-            return ValidationProblem("页码必须大于 0，且每页条数应在 1 至 100 之间。");
+        if (pageSize is < 1 or > 100)
+            return ValidationProblem("每批条数应在 1 至 100 之间。");
+        if (!CursorToken.TryDecode<CreatedCursor>(cursor, out var after))
+            return BadRequest("调停课申请游标无效。");
 
         var userId = currentUserDataScope.Current.UserId;
         var source = db.CourseAdjustments.AsNoTracking()
@@ -193,15 +195,27 @@ public sealed class CourseAdjustmentsController(
         if (status.HasValue)
             source = source.Where(x => x.Status == status);
 
-        var total = await source.CountAsync(cancellationToken);
-        var items = await source
+        if (after is not null)
+        {
+            source = source.Where(x => x.CreatedAt < after.CreatedAt ||
+                x.CreatedAt == after.CreatedAt && x.Id.CompareTo(after.Id) < 0);
+        }
+        var keys = await source
             .OrderByDescending(x => x.CreatedAt)
             .ThenByDescending(x => x.Id)
-            .Skip((page - 1) * pageSize)
-            .Take(pageSize)
-            .Select(AdjustmentProjection())
+            .Take(pageSize + 1)
+            .Select(x => new { x.Id, x.CreatedAt })
             .ToListAsync(cancellationToken);
-        return Ok(new PagedResult<object>(items, total, page, pageSize));
+        var hasMore = keys.Count > pageSize;
+        var pageIds = keys.Take(pageSize).Select(x => x.Id).ToArray();
+        var items = await source.WhereIn(pageIds, x => x.Id)
+            .OrderByDescending(x => x.CreatedAt).ThenByDescending(x => x.Id)
+            .Select(AdjustmentProjection()).ToListAsync(cancellationToken);
+        var last = keys.Take(pageSize).LastOrDefault();
+        return Ok(new CursorPagedResult<object>(items,
+            hasMore && last is not null
+                ? CursorToken.Encode(new CreatedCursor(last.CreatedAt, last.Id)) : null,
+            hasMore, pageSize));
     }
 
     // ═══════════════ Pending reviews ═══════════════
@@ -210,13 +224,15 @@ public sealed class CourseAdjustmentsController(
     [Authorize(Roles = Reviewers)]
     public async Task<ActionResult> GetPendingReviews(
         Guid? academicTermId,
-        int page = 1,
+        string? cursor = null,
         int pageSize = 20,
         CancellationToken cancellationToken = default,
         Guid? adjustmentId = null)
     {
-        if (page < 1 || pageSize is < 1 or > 100)
-            return ValidationProblem("页码必须大于 0，且每页条数应在 1 至 100 之间。");
+        if (pageSize is < 1 or > 100)
+            return ValidationProblem("每批条数应在 1 至 100 之间。");
+        if (!CursorToken.TryDecode<SubmittedCursor>(cursor, out var after))
+            return BadRequest("待审核调停课游标无效。");
 
         var scope = currentUserDataScope.Current;
         var source = db.CourseAdjustments.AsNoTracking()
@@ -230,17 +246,32 @@ public sealed class CourseAdjustmentsController(
             source = source.Where(x =>
                 x.TeachingTask!.AcademicTermId == academicTermId);
 
-        var total = await source.CountAsync(cancellationToken);
-        var items = await source
+        if (after is not null)
+        {
+            source = source.Where(x => x.SubmittedAt!.Value < after.SubmittedAt ||
+                x.SubmittedAt == after.SubmittedAt && x.Id.CompareTo(after.Id) < 0);
+        }
+        var keys = await source
             .OrderByDescending(x => x.SubmittedAt)
             .ThenByDescending(x => x.Id)
-            .Skip((page - 1) * pageSize)
-            .Take(pageSize)
-            .Select(AdjustmentProjection())
+            .Take(pageSize + 1)
+            .Select(x => new { x.Id, SubmittedAt = x.SubmittedAt!.Value })
             .ToListAsync(cancellationToken);
-        return Ok(new PagedResult<object>(items, total, page, pageSize));
+        var hasMore = keys.Count > pageSize;
+        var pageIds = keys.Take(pageSize).Select(x => x.Id).ToArray();
+        var items = await source.WhereIn(pageIds, x => x.Id)
+            .OrderByDescending(x => x.SubmittedAt).ThenByDescending(x => x.Id)
+            .Select(AdjustmentProjection()).ToListAsync(cancellationToken);
+        var last = keys.Take(pageSize).LastOrDefault();
+        return Ok(new CursorPagedResult<object>(items,
+            hasMore && last is not null
+                ? CursorToken.Encode(new SubmittedCursor(last.SubmittedAt, last.Id)) : null,
+            hasMore, pageSize));
     }
 
+    private sealed record CreatedCursor(DateTime CreatedAt, Guid Id);
+    private sealed record SubmittedCursor(DateTime SubmittedAt, Guid Id);
+
     // ═══════════════ Detail ═══════════════
 
     [HttpGet("{id:guid}")]