游标分页优化

src/Jiaowu.Api/Controllers/AppUpdatesController.cs

@@ -113,15 +113,17 @@ public sealed partial class AppUpdatesController(AppDbContext db) : ControllerBa
 
     [Authorize(Roles = SystemRoles.SuperAdmin)]
     [HttpGet("releases")]
-    public async Task<ActionResult<PagedResult<AppUpdateReleaseItem>>> GetReleases(
-        [FromQuery] int page = 1,
+    public async Task<ActionResult<CursorPagedResult<AppUpdateReleaseItem>>> GetReleases(
+        [FromQuery] string? cursor = null,
         [FromQuery] int pageSize = 20,
         [FromQuery] string? platform = null,
         [FromQuery] string? channel = null,
         CancellationToken cancellationToken = default)
     {
-        if (page < 1 || pageSize is < 1 or > 100)
-            return ValidationProblem("页码必须大于零，每页数量必须在 1 到 100 之间。");
+        if (pageSize is < 1 or > 100)
+            return ValidationProblem("每批数量必须在 1 到 100 之间。");
+        if (!CursorToken.TryDecode<ReleaseCursor>(cursor, out var after))
+            return BadRequest("更新包游标无效。");
 
         var query = db.AppUpdateReleases.AsNoTracking().AsQueryable();
         if (!string.IsNullOrWhiteSpace(platform))
@@ -137,11 +139,21 @@ public sealed partial class AppUpdatesController(AppDbContext db) : ControllerBa
             query = query.Where(x => x.Channel == parsedChannel);
         }
 
-        var total = await query.CountAsync(cancellationToken);
-        var rows = await query
+        if (after is not null)
+        {
+            query = query.Where(x => (x.PublishedAt ?? x.CreatedAt) < after.SortAt ||
+                (x.PublishedAt ?? x.CreatedAt) == after.SortAt && x.Id.CompareTo(after.Id) < 0);
+        }
+        var keys = await query
             .OrderByDescending(x => x.PublishedAt ?? x.CreatedAt)
-            .Skip((page - 1) * pageSize)
-            .Take(pageSize)
+            .ThenByDescending(x => x.Id)
+            .Take(pageSize + 1)
+            .Select(x => new { x.Id, SortAt = x.PublishedAt ?? x.CreatedAt })
+            .ToArrayAsync(cancellationToken);
+        var hasMore = keys.Length > pageSize;
+        var pageIds = keys.Take(pageSize).Select(x => x.Id).ToArray();
+        var rows = await query.WhereIn(pageIds, x => x.Id)
+            .OrderByDescending(x => x.PublishedAt ?? x.CreatedAt).ThenByDescending(x => x.Id)
             .Select(x => new AppUpdateReleaseItem(
                 x.Id,
                 x.Platform,
@@ -158,13 +170,16 @@ public sealed partial class AppUpdatesController(AppDbContext db) : ControllerBa
                 x.PublishedByUserName,
                 x.PublishedAt))
             .ToArrayAsync(cancellationToken);
-        return Ok(new PagedResult<AppUpdateReleaseItem>(
+        var last = keys.Take(pageSize).LastOrDefault();
+        return Ok(new CursorPagedResult<AppUpdateReleaseItem>(
             rows,
-            total,
-            page,
+            hasMore && last is not null ? CursorToken.Encode(new ReleaseCursor(last.SortAt, last.Id)) : null,
+            hasMore,
             pageSize));
     }
 
+    private sealed record ReleaseCursor(DateTime SortAt, Guid Id);
+
     [Authorize(Roles = SystemRoles.SuperAdmin)]
     [Consumes("multipart/form-data")]
     [RequestSizeLimit(MaximumBundleBytes + 1024 * 1024)]